bluuebunny/crossref_metadata_2025 huggingface dataset:
Preparation and characteristic of phase transition vanadium oxide thin films by rapid thermal process
Authors: Wu Bin  , Hu Ming  , Hou Shun-Bao  , Lü Zhi-Jun  , Gao Wang  , Liang Ji-Ran  ,   School of Electronic Information Engineering, Tianjin University, Tianjin 300072, China
Published: December 2020

Metal-insulator phase transition VOX thin film is fabricated on a Si 100 substrate after the metal V thin film, prepared by direct current facing targets magnetron sputtering has been rapidly thermally treated first in pure oxygen environment and then in pure nitrogen environment. The thermal treatment conditions are 430℃/40 s, 450℃/40 s, 470℃/40 s, 450℃/30 s, 450℃/50 s in pure oxygen environment and 500℃/15 s in pure nitrogen environment. XRD, XPS, AFM and SEM are imployed to analyze the crystalline structure, valentstate and the components, morphology of the thin film. The electrical and optical characteristic of the thin film are analyzed by the Four-point probe method and THz time domain spectrum technology. Results reveal that after 450℃/40 s rapid thermal treatment in pure oxygen environment the metal V thin film turns into VOX thin film which has low properties of phase transition. Before and after heating, the change of resistivity reaches 2 orders of magnitude and the range of the THz transmission intensity shows smooth change. In order to improve the properties of phase transition, the VOX thin film is treated by 500℃/15 s rapid thermal process in pure nitrogen environment. After that, we find that the thin film shows a good phase transition performance, accompanied by a sheet square resistance drop of above 3 orders of magnitude and a 56.33% reduction in THz transmission intensity.
Aberrations in holographic array optical tweezers corrected with Zernike polynomials
Authors: Liu Wei-Wei  , Ren Yu-Xuan  , Gao Hong-Fang  , Sun Qing  , Wang Zi-Qiang  , Li Yin-Mei  ,   Department of Optics and Optical Engineering, University of Science and Technology of China, Hefei 230026, China;,   Hefei National Laboratory for Physical Sciences at the Microscale, Hefei 230026, China
Published: December 2020

Aberrations will degrade trapping performance of optical tweezers. In the holographic optical tweezers, aberrations originate not only from optical elements but also from holographic phase hologram of optical traps designed by a certain algorithm. We utilize a spatial light modulator to imprint Zernike polynomials phase hologram for correcting some certain aberrations in holographic array optical tweezers which are caused by grating and lens algorithm. The results show that third-order Zernike term can effectively correct coma due to the algorithm in the optical train, and the trap stiffness for 2 μm microns diameter polystyrene beads can reach 40%. Further comparison between different Zernike term aberration correction effects demonstrates that coma caused by grating and lens algorithm in the holographic array optical tweezer has the same serious influence on tweezer trapping performance as the aberrations originating from optical elements. Meanwhile, based on first-order Zernike term aberration correction results it can be obtained that grating and lens algorithm are robust with first-order Zernike aberrations. The correcting of aberrations for algorithm in holographic optical tweezers has great significance for improving the tweezer trapping performance and deepening the understanding of specific algorithm.
The critical warning research of the mean time series mutations based on Logistic model
Authors: Yan Peng-Cheng  , Hou Wei  , Hu Jing-Guo  ,   Department of Physics, Yangzhou University, Yangzhou 225002, China;,   National Climate Center, China Meteorological Administration, Beijing 100081, China;,   College of Physics and Electronic Engineering, Northwest Normal University, Lanzhou 730070, China
Published: December 2020

In this paper, we analyze the stability of solution of the nonlinear function of physics, the Logistic function. It is found that the solution has a special character that it can change abruptly from one stable state to another when the initial value and parameters of function are selected. Abrupt change level and abrupt change rate are related to parameters of function, which can be described by defining the abrupt change intensity index. By using the character of solution, we build an ideal time series to imitate climate abrupt change in mean of climate system, investigate what behaviors the recovery rate and recovery force can have when the system approaches to a critical threshold, and to ascertain how it warns the abrupt change of the system early. Besides, we also find that even the system is disturbed by some noise signals, the recovery rate and recovery force also make an early response to the arrival of the abrupt change of system. Finally, the result of testing the Pacific Decadal Oscillation (PDO) index showes that the early warning of the abrupt change appeared in 1973, much more early than the abrupt change of PDO index happening in 1976/1977, which means that the recovery rate and recovery force can be used as the early warning signals of the abrupt change in mean.
A finite volume algorithm for solving nonlinear standing waves in acoustic resonators
Authors: Ning Fang-Li  , Dong Liang  , Zhang Wen-Zhi  , Wang Kang  ,   School of Mechanical Engineering, Northwestern Polytechnical University, Xi'an 710072, China
Published: December 2020

In order to expand the engineering application area of nonlinear standing waves in acoustic resonators, a new numerical algorithm is proposed for simulating nonlinear standing waves in resonators. It also can be used to overcome the shortages of the existing numerical methods, which restrict the solution to the nonlinear standing waves in cylindrical resonators and exponential resonators. The numerical algorithm is constructed based on the Navier-Stokes equations in the resonators with variable cross-section for an unsteady compressible thermoviscous fluid without truncation, and the space conservation law. The numerical algorithm-finite volume method for solving the nonlinear standing waves in acoustic resonators by piston driving is built based on the semi-implicit method for pressure-linked equations-consistent algorithm and staggered grid technique. Simulations for solving the nonlinear standing waves in cylindrical resonators, exponential resonators and conical resonators are carried out. By comparison with the existing experimental results and numerical simulation results, the accuracy of the developed finite volume algorithm is verified. Some new physical results are obtained, including unsteady velocity, density and temperature. The shock-like pressure wave shapes are found in cylindrical resonators, simultaneously, and the results show that the sharp velocity spikes appear in the cylindrical resonators. High amplitude acoustic pressures are generated in exponential resonators and conical resonators. Shock-like pressure waves and the sharp velocity spikes are not found. The strong dependence of the physical properties of nonlinear standing waves on resonator shape is demonstrated through the simulative results.
Eliminate spiral wave and spatiotemporal chaos by using short-term cardiac memory
Authors: Kuang Yu-Lan  , Tang Guo-Ning  ,   College of Physics and Technology, Guangxi Normal University, Guilin 541004, China
Published: December 2020

Cardiac memory effect, which exhibits the time-delayed coupling of membrane voltage, is introduced into Luo-Rudy phase I cardiac model. The effect of the cardiac memory on spiral waves is investigated. The numerical results show that the cardiac memory can lead to irregular meandering of spiral waves. When the delay-time is properly chosen, the increase of memory strength causes the decrease of spiral wave frequency. If memory strength exceeds the critical value, the cardiac memory results in the disappearances of both spiral waves and spatiotemporal chaos in system because the time-dependent potassium ion current is over suppressed by cardiac memory.
Fractional differentiability of the non-smooth heat curve
Authors: Wu Guo-Cheng  , Shi Xiang-Chao  ,   College of Water Resources and Hydropower, Sichuan University, Chengdu 610065, China
Published: December 2020

There are many non-smooth objects in nature, such as coastline, rock fracture, cross section, whose differentiabilities cannot be described by ordinary calculus and methods in Euclidean geometry. The local fractional derivative is one of the potential tools to investigate the non-smooth problems. This study revisits the non-smooth curves generated from the fractional integrals and Cantor-like set. From the view of the fractional differentiable functions, the differentiabilities of the non-smooth curves are derived by using a binomial expansion.
Heart rate variability analysis based on modified Poincaré plot
Authors: Huo Cheng-Yu  , Zhuang Jian-Jun  , Huang Xiao-Lin  , Hou Feng-Zhen  , 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;,   School of Physics and Electronic Engineering, Changshu Institute of Technology, Changshu 215500, China
Published: December 2020

Poincaré plot is an important method in nonlinear analysis of heart rate variability(HRV). Based on the modified Poincaré plot, two arguments-the regional distribution entropy and regional distribution coefficient are put forward for the quantitative description of the scatter distribution trends in the studied area. And the distributions of the Poincaré plot in the four quadrants are calculated separately. Through the analysis of the HRV sample data from healthy young people, older people and congestive heart failure(CHF) sufferers in MIT-BIH database, we find that the two parameters show a significant difference between the groups. Meanwhile, the analysis results in different quadrants show that the sensitivities of the four quadrants are different, and especially in the first quadrant, the sensitivity is best. This phenomenon shows that the changes of vagal control function are most significant between healthy people and CHF sufferers, which is consistent with previous physiological research conclusion. Experimental results also show that the method can be used for short-term data, and thus is easier to extend to clinical applications.
Opinion formation on the social networks with geographic structure
Authors: Luo Zhi  , Yang Guan-Qiong  , Di Zeng-Ru  ,   School of Management, Beijing Normal University, Beijing 100875, China
Published: December 2020

Opinion formation is the result of co-evolution of individual behavior and environment. Individual behavior is determined by its rational cognition and irrational emotion. Environment includes culture, cognitive and behavioral patterns and social interactions. Culture and cognitive patterns are usually related to the spatial factors. In this paper, a social network with geographical factors is constructed. Together with the Ising model in networks, the effects of both spatial and social factors on opinion formation are investigated. The phase transition in the process of opinion formation is studied. The results indicate that both spatial cultural background and global preference for public opinion are crucial to opinion formation.
The study of dielectronic recombination (DR) rate coefficient for ground state of Ne-like isoelectronic sequence ions
Authors: Yang Jian-Hui  , Fan Qiang  , Zhang Jian-Ping  ,   College of Physics and Electronic Engineering, Leshan Normal University, Leshan 614004, China
Published: December 2020

The dielectronic recombination (DR) rate coefficients for Ne-like isoelectronic sequence ions in the ground state 2s22p6 are calculated by using relativistic configuration interaction (RCI) method over a wide temperature ranging from 0.1EI to 10EI where EI is the ionization energy of corresponding Na-like ion. The (2s2p)73ln'l', (2s2p)74l4l' and (2s2p)74l5l' complexes are considered as autoionizing doubly excited states of Ne-like ions in the calculation. The contribution of (2s2p)73ln'l' complex with l' >8 is found to be negligible. The contribution of high Rydberg states of (2s2p)73ln'l' complex obeys the complex-complex n'-3 extrapolation, and the larger the nuclear charge, the smaller the value of n' is. On the basis of the detailed level-by-level results, a general analytic formula for the total DR rate coefficient for all the ions along the Ne-like isoelectronic sequence is constructed. This formula can generally reproduce the calculated DR rate coefficients within 2% for electron temperature between 0.1EI and 10EI. Burgess-Merts semiempirical formula is found to be inadequate for predicting the DR rates of Ne-like ions at low electron temperatures (kTeEI) and may be used for high electron temperatures (kTe > 2EI).
First-principles study on the electronic and optical property of C-Zn co-doped anatase TiO2
Authors: Wang Yin  , Feng Qing  , Wang Wei-Hua  , Yue Yuan-Xia  ,   Key Laboratory of Optics and Engineering, Chongqing Normal University, Chongqing 400047, China
Published: December 2020

In recent years, many theoretical and experimental researches have reported that different atoms doping TiO2 is one of the effective methods to reduce the gap. In this paper, the band structure, density of states and optical property of C-Zn co-doped rutile TiO2 are studied by the plane-wave ultrasoft pseudopotential method based on the first-principles density functional theory. The calculations show that C-Zn co-doped TiO2 results in the conductor band apparently shifted down to the Fermi level. Some impurity energy levels of co-doped TiO2 are below the conduction band minimum, and others are above the valence band maximum. The distance between them narrows down, which results in the redshift of the optical absorption edges to visible-light region. These impurity energy levels can reduce the recombination rate of photoexcited carriers and improve the photocatalytic efficiency of TiO2. Besides, the optical absorption coefficient becomes larger in visible-light region and the energy loss decreases clearly.
Coherence effect of high excited state atoms
Authors: Zhao Jian-Dong  , Xin Jie  ,   College of Information and Communication Engineering, North University of China, Taiyuan 030051, China
Published: December 2020

The ladder three-level system including ground state, excited state and high excited state is investigated by using the density matrix equations. The coherence effect of ladder three-level system is analyzed, and absorption and dispersion curves of weak probe laser are obtained. The effects of interaction between high excited atoms and external electric field on the coherence effect are also investigated. The result shows that the interaction between high excited atoms or the external field can make the absorption curve and the dispersion curve shifted.
Cross-polarizaton characteristics in spin Hall effect of light
Authors: Luo Xing  , Zhou Xin-Xing  , Luo Hai-Lu  , Wen Shuang-Chun  ,   Key Laboratory for Micro/Nano Optoelectronic Devices of Ministry of Education, School of Information Science and Engineering, Hunan University, Changsha 410082, China
Published: December 2020

From the angular spectrum theory of beam, we obtain a transmission model in the paraxial approximation which describes the spin Hall effect of light, and we use this model to analyze the cross-polarization characteristics in spin Hall effect of light. By analyzing the change of cross-polarization intensity and incident angles we find that the spin splitting in spin Hall effect of light becomes stronger when cross-polarization effect is stronger. In order to facilitate the experimental observation, we choose the incident angle near the Brewster angle where it's spin Hall effect of light is much more evident, and from where we observe a strong cross-polarization effect. If we increase the cross-polarization components and reduce the light of original polarization direction at the same time, the spin Hall effect of light can be greatly enhanced. This is a promising method to develop new optical devices based on spin Hall effect of light.
The absorption spectrum study of the (4, 0) band in the b4Σ--a4Πi system of NO
Authors: Deng Lun-Hua  , Li Chuan-Liang  , Zhu Yuan-Yue  , He Wen-Yan  , Chen Yang-Qin  ,   State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai 200062, China;,   Taiyuan University of Science and Technology, Applied Science and Technology, Department of Physics, TaiYuan 030024, China
Published: December 2020

The absorption spectrum of NO is analyzed in a range of 12530-12850 cm-1 using optical heterodyne concentration modulation spectroscopy in an AC glow discharge of He/NO mixture. Among all the spectral lines, 324 lines are assigned to the (4, 0) band and 267 ones are fitted to the Hamiltonians of the b4Σ--a4Πi system by a non-linear least-square fitting procedure. A residual (0.0071 cm-1) comparable to system error (0.0071 cm-1) is obtained. The main molecular constants are consistent with those reported in the literature and the fine structure constants are fitted.
The gain spectrum character under Raman scattering and parametric amplification
Authors: Jia Wei-Guo  , Qiao Li-Rong  , Wang Xu-Ying  , Ke Neimule  , Yang Jun  , Zhang Jun-Ping  ,   School of Physical Science and Technology, Inner Mongolia University, Hohhot 010021, China;,   Inner Mongolia Radio & TV University, Hohhot 010010, China
Published: December 2020

According to the nonlinear coupled equation under the joint action of Raman scattering and parametric amplification when the optical pulse propagats in the birefringent fiber, based on Lorentzian model of parallel Raman gain spectrum, the gain spectrum is obtained by combining Raman scattering and parametric amplification when the pump wave polarization direction is along the two orthogonal birefringence axes. The gain spectrum is discussed as a function of input parameters (input power, the group velocity mismatch) in different dispersion regimes. The result shows that the balance between non-linearity and dispersion is destructed by Raman scattering. Stokes and anti-stokes gain spectrum are asymmetric because of Raman effect. The structure of gain spectrum is confirmed when input power is constant. The intensity and width of gain spectrum change with dispersion and nonlinear parameter.
Generation of photonic microwave based on the period-one oscillation of an optically injected semiconductor lasers and all-optical linewidth narrowing
Authors: Lin Xiao-Dong  , Deng Tao  , Xie Yi-Yuan  , Wu Jia-Gui  , Chen Jian-Guo  , Wu Zheng-Mao  , Xia Guang-Qiong  ,   School of Electronics and Information Engineering, Sichuan University, Chengdu 610064, China;,   School of Physics Science and Technology, Southwest University, Chongqing 400715, China
Published: December 2020

Based on the single period dynamics of optically injected semiconductor laser, the generation of photonic microwave and its linewidth narrowing effect by introducing optical feedback are experimentally demonstrated. The experimental results show that the photonic microwave frequency can be continuously and widely tuned in a range of several ten GHz by adjusting the injection parameters. By introducing an optical feedback and properly adjusting the feedback strength, the photonic microwave linewidth is reduced by about two orders of magnitude from a range of 40-100 MHz to a range of 300-900 kHz. The influence of optical feedback length on the microwave linewidth is not obvious except that the photonic microwave frequency exhibits an periodical variation in a small range when the feedback length is finely varied in a small range.
Forced oscillations of gaseous bubbles in microtubules
Authors: Wang Cheng-Hui  , Cheng Jian-Chun  ,   Institute of Acoustics, Nanjing University, Nanjing 210093, China;,   Institute of Applied Acoustics, Shaanxi Normal University, Xi'an 710062, China
Published: December 2020

Based on the model for the one-dimensional coupled oscillation of bubble-liquid column in tube, a theoretical investigation of the forced oscillation of a cylindrical gaseous bubble in a microtubule is presented. For the case that the two acoustic pressures of microtubule ends are not homogenous, the linear natural frequency is not affected, but its oscillating amplitude is influenced by the effective acoustic pressure amplitude. The relations between the amplitudes of fundamental, third and one third harmonic oscillations and the acoustic frequency are analyzed using the succession-level approximation method. Numerical results show that the bubble oscillates nonlinearly if the effective value of acoustic pressure exceeds 0.1MPa. It is found that the amplituds of fundamental, third and one third harmonic oscillations are multivalued, and the response of third harmonic oscillation is stronger in the region of lower frequencies. Furthermore, the third harmonic oscillation may be probably induced in the region of ω/ω0 ≥ 1.
Lyapunov-Schmidt reduction and singularity analysis of a high-dimensional relative-rotation nonlinear dynamical system
Authors: Shi Pei-Ming  , Han Dong-Ying  , Li Ji-Zhao  , Jiang Jin-Shui  , Liu Bin  ,   College of Electrical Engineering, Yanshan University, Qinhuangdao 066004, China;,   College of Vehicles and Energy, Yanshan University, Qinhuangdao 066004, China
Published: December 2020

The dimensionality reduction and bifurcation of some high-dimensional relative-rotation nonlinear dynamical system are studied. Considering the nonlinear influence factor of a relative-rotation nonlinear dynamic system, the high-dimensional relative-rotation torsional vibration global dynamical equation is established based on Lagrange equation. The equivalent low-dimensional bifurcation equation, which can reveal the low-dimensional equivalent bifurcation equation between the nonlinear dynamics and parameters, can be obtained by reducing the dimensionality system using the method of Lyapunov-Schmidt reduction. On this basis, the bifurcation characteristic is analyzed by taking universal unfolding on the bifurcation equation through using the singularity theory. The simulation is carried out with actual parameters. The parameter region of torsional vibration and the effect of the parameters on the vibration are discussed.
Mechanism analysis of one-dimensional short groove quasicrystal structure drag-reduction
Authors: Zhang Meng  , Geng Xing-Guo  , Zhang Yao  , Wang Xiao-Na  ,   School of Science, Northwestern Polytechnical University, Xi'an 710072, China
Published: December 2020

Short groove arranged in one-dimensional quasicrystal structure is designed by mechanical method in this paper and drag reduction experiments are performed by viscometer. The results show that there is a novel drag reduction effect compared with periodic structure of one-dimensional short groove, in which 12-fold quasicrystal structure of one-dimensional short groove has the best drag reduction, and has an equal effect compared with one-dimensional periodic groove structure. An two-dimensional grating model is proposed to investigate the mechanism. It is found that in comparison with two-dimensional periodic grating, the intensity spectrum of coherent wave passing through two-dimensional quasiperiodic grating has several characteristic structure factors. Corresponding to the quasicrystal structures of one-dimensional short groove, the quasiperiodic structure in spanwise direction can activate little disturbance on boundary layer and make the secondary vortex more uniform, which restrains the strong disturbance in spanwise, consequently reducing the drag.
First-principles study on the electronic structure and phase transition of α-, β- and γ-Si3N4
Authors: Yu Ben-Hai  , Chen Dong  ,   College of Physics and Electronic Engineering, Xinyang Normal University, Xinyang 464000, China
Published: December 2020

The high-temperature lattice constants and elastic moduli of the silicon nitrides are calculated using the plane-wave pseudo-potential method combined with the vibrational Debye-like model. β-Si3N4 is ductile at low temperature and brittle at high temperature. γ-Si3N4 is found to be brittle and covalent in nature. We find a positive slope of the β→γ phase boundary, hence, at higher temperatures it requires higher pressures to synthesize γ -Si3N4. The α → γ phase boundary may be expressed as P=16.29-1.835-10-2 T+9.33945-10-5T2-2.16759-10-7 T3+2.91795-10-10T4. We also obtain the electronic structures and energy bands of Si3N4 with and without pressure. The interaction between Si-s, p and N-s, p plays a dominant role in the stability of α-Si3N4. The α- and β-Si3N4 have the ΓV-ΓC indirect band gaps (4.9~eV and 4.4~eV) while γ-Si3N4 has a direct band gap(3.9~eV). The tops of the valence bands for α- and β-Si3N4 are along the Γ-M and Γ-A direction, respectively. Our results are consistent with the experimental data and the theoretical results.
Research on the electromagnetic properties of nano-fiber coating absorbent
Authors: Fu Cheng-Wu  , Zhang Shuan-Qin  , Chen Ming-Qing  ,   The Key Laboratory of Food Colloids and Biotechnology, Ministry of Education, School of Chemical and Material Engineering, Jiangnan University, Wuxi 214122, China;,   The First Engineers Scientific Research Institute of the General Armaments Department, Wuxi 214035, China
Published: December 2020

Electrochemical method is used to fabricate nano-fiber coating absorbent. The effect of the fiber length on electromagnetic property is analyzed. Radar absorbing coating is prepared preferentially. The measurements show that nano-fiber coating absorbent has good absorbing properties.
Phenomenological analysis for dielectric dispersion of donor doped barium titanate based relaxor ferroelectric
Authors: Shang Yu-Li  , Shu Ming-Fei  , Chen Wei  , Cao Wan-Qiang  ,   School of Materials Science and Engineering, Hubei University, Wuhan 430062, China
Published: December 2020

Dielectric dispersion of relaxor ferroelectric in diffusion region is related to the doping of extrinsic ions or ordering arrangement of intrinsic ions. The further explanation and unitive characterization of the dispersion property are required. Focusing on the facts that cation vacancies and dielectric dispersion in barium titanate based relaxor ferroelectric can be caused by donor doping in high concentration, three equivalently correlated Gaussian distributions of doping dopants, Curie temperature, and cation vacancy are obtained. The relevant Gibbs free energy and relation between dielectric constant and temperature of the relaxors with donor doping are deduced. The result demonstrates an increase in concentration of cation vacancy with temperature decreasing in diffusion transition region. The unipole charges caused by the cation vacancies are probably responsible for the dielectric dispersion and loss by their hopping motion.
Effects of pulsed magnetic field on Mn-doped ZnO diluted magnetic semiconductor prepared by hydrothermal method
Authors: Wang Shi-Wei  , Zhu Ming-Yuan  ,  Zhong Min  , Liu Cong  , Li Ying  , Hu Ye-Min  , Jin Hong-Ming  ,   Laboratory for Microstructures, School of Materials Science and Engineering, Shanghai University, Shanghai 200072, China
Published: December 2020

In this study, zinc acetate, manganese acetate, ammonium hydroxide and ammonium chloride are used as the source materials to prepare crystalline Mn-doped ZnO diluted magnetic semiconductor by hydrothermal method under a 4 T pulsed magnetic field. The microstructures, morphologies and magnetic properties of the samples are characterized by X-ray diffraction, scanning electron microscope, transmission electron microscope, Raman scattering spectra, Photoluminescnce and vibrating sample magnetometer. The effect of pulsed magnetic field on the microstructure and magnetic property of the Mn-doped ZnO diluted magnetic semiconductor are discussed. The result indicates that all the samples are still of hexagonal wurtzite structure. The pulsed magnetic field promotes the crystal growth, and improves room temperature ferromagnetism. The saturation magnetization (0.028 emu/g) of the sample fabricated under 4 T pulsed magnetic field is more than two times that of the sample synthesized without pulsed magnetic field. The Curie temperature (Tc) of the Mn-doped ZnO increases 15 K through the pulsed magnetic field processing.
Effect of electromigration on interfacial reaction in Ni/Sn3.0Ag0.5Cu/Au/Pd/Ni-P flip chip solder joints
Authors: Huang Ming-Liang  , Chen Lei-Da  , Zhou Shao-Ming  , Zhao Ning  ,   School of Materials Science and Engineering, Key Laboratory of Liaoning Advanced Welding and Joining Technology, Dalian University of Technology, Dalian 116024, China
Published: December 2020

The effect of electromigration (EM) on the interfacial reaction in the Ni/Sn3.0Ag0.5Cu/Au/Pd/Ni-P flip chip solder joint is investigated under a current density of 1.0× 104 A/cm2 at 150℃. The (Cu,Ni)6Sn5 intermetallic compounds (IMCs) form at both solder/Ni and solder/Ni-P interfaces in the as-reflowed state. During aging at 150℃, the (Cu,Ni)6Sn5 interfacial IMCs grow thicker and transform into (Ni,Cu)3Sn4 type after 200 h at solder/Ni interface and 600 h at solder/Ni-P interface, respectively. During EM, the current direction plays an important role in Ni-P layer consumption. When electrons flow from Ni-P to Ni, EM enhances the consumption of Ni-P, i.e., the Ni-P s completely consumed and transforms into Ni2SnP after EM for 600 h. There is no Cu-Sn-Ni ternary IMC at the solder/Ni-P interface (cathode). Crack forms at the Ni2SnP/Cu interface due to the weak bonding force between Ni2SnP and Cu. When electrons flow from Ni to Ni-P, no obvious consumption of Ni-P is observed during EM; the current crowding effect induces a rapid and localized dissolution of Ni UBM and Cu pad at the chip side (cathode). The dissolved Ni and Cu atoms are driven along the flowing direction of electrons and form a large number of IMC particles in the solder matrix. During EM, the (Au,Pd,Ni)Sn4 phase prefers to be redistributed only at the anode interface, regardless of the direction of electron flow.
Research on sodium incorporation methods of growing Cu(In-Ga)Se2 thin film by low-temperature deposition
Authors: He Jing-Jing  , Liu Wei  , Li Zhi-Guo  , Li Bo-Yan  , Han An-Jun  , Li Guang-Min  , Zhang Chao  , Zhang Yi  , Sun Yun  ,   Institute of Photo-Electronics Thin Film Devices and Technique, College of Information Technical Science, Nankai University, Tianjin 300071, China
Published: December 2020

Sodium is proved to be able to improve the performance of Cu(In,Ga)Se2 solar cell grown on flexible polyimide substrate by a low-temperature deposition. Different sodium incorporation methods affect the film in different ways. Comparing the deposition of a NaF precursor with post deposition NaF treatment, different mechanisms can be found. In NaF precursor approach, Na is available during the Cu(In,Ga)Se2 growth and acts as a surfactant at the grain boundary which adds up an energy barrier for adatom to across. Thus, a small grain size as well as double-peak reflection pattern can be observed and the formation probability of donor defects is reduced. In post deposition NaF treatment, incorporation of NaF does not affect the growth and microstructure but passivates donor defects in the Cu(In,Ga)Se2 film. Moreover, according to the experimental results, external energy assistance is necessary during NaF incorporation through post deposition treatment. It is verified that Na incorporation is able to improve the properties of the film effectively when substrate temperature reaches above 350 ℃. Finally, the conversion efficiency of flexible Cu(In,Ga)Se2 thin film solar cell on polyimide substrate is achieved to be 10.4% by optimizing the sodium incorporation.
A mechanism analysis of the interdecadal precipitation change in Northwestern China for the last 30 years of twentieth century
Authors: Dai Xin-Gang  , Zhang Kai-Jing  ,   RCE-TEA, Institute of Atmospheric Physics, CAS, Beijing 100029, China;,   Qindao Meteorological Service, Qingdao 266003, China
Published: December 2020

There took place an inter-decadal climate change over the west part of Northwestern China at mid-1980s. One of the significant characteristics is the increase in precipitation with more extreme rainfall or snowfall event. For understanding its mechanism our calculation focuses on the difference of the geo-potential height on 500 hPa, transient eddy activity, column water vapor content or precipitable water, moisture transport and its divergence between 1987-2000 and 1973-1986. The results show that the change in height field is favorable for the increase in moisture transport to the region with moisture convergence, leading to more water vapor over the region. Meanwhile the eddy activity became weak in wintertime and strong in summertime, leading to more synoptic processes in summertime and less in wintertime. A further decomposition shows that the increase in the transport with convergence was contributed mainly by its stationary-wave part along the west-east direction, while the transient eddy played a positive role in summertime and a negative one in wintertime for precipitation. It turns out that the increase in precipitation in the region resulted from the moisture convergence and the increase in eddy activity in summertime while the moisture convergence played a dominant role in wintertime. Besides, the warming climate also played a positive role in increasing air water-vapor content in the region since the warm air can hold more water vapors than the cold one.
Conformal invariance, Mei symmetry and the conserved quantity of the Kepler equation
Authors: Liu Hong-Wei  , Li Ling-Fei  , Yang Shi-Tong  ,   Institute of Mathematics, Jilin University, Changchun 130012, China;,   School of Sciences, Northeast Dianli University, Jilin 132012, China
Published: December 2020

In this paper, the conformal invariance and Mei symmetry of Kepler system under infinitesimal transformations are discussed in detail. The new conserved quantity of the system is given, which is different from the total energy and the angular momentum. The independences of these conserved quantities are discussed in the space which is composed of general ordinates and general speed.
Mei symmetry and Mei conserved quantity of Nielsen equation in a dynamical system of the relative motion with nonholonomic constraint of Chetaev's type
Authors: Wang Xiao-Xiao  , Zhang Mei-Ling  , Han Yue-Lin  , Jia Li-Qun  ,   School of Science, Jiangnan University, Wuxi 214122, China
Published: December 2020

Mei symmetry and Mei conserved quantity of Nielsen equations in a dynamical system of the relative motion with nonholonomic constraint of Chetaev's type are studied. The differential equations of motion of Nielsen equation for the system, the definition and criterion of Mei symmetry, and the expression of Mei conserved quantity deduced directly from Mei symmetry for the system are obtained. An example is given to illustrate the application of the results.
The physical significances and applications of Schmidt decompositions of continuum bipartile entangled state representation
Authors: Fan Hong-Yi  , Li Xue-Chao  ,   Department of Material Science and Engineering, University of Science and Technology of China, Hefei 230026, China;,   Department of Modern Physics, University of Science and Technology of China, Hefei 230026, China
Published: December 2020

According to the continuum bipartite entangled state representation |η> we derive the Schmidt decomposition of |η>, respectively in the coordinate representation, momentum representation and the particle number representation, and explain their physical significances. As the applications of the Schmidt decomposition, we directly derive the action of the single-mode squeeze operator on |η>, the two-mode squeeze operator's entangled state representation, as well as the matrix element of displacement operator in the Fock space. Generalization of our discussion in this paper to the multipartite entangled state cases is feasible.
Research of Lyapunov exponent of S-boxes
Authors: Zang Hong-Yan  , Fan Xiu-Bin  , Min Le-Quan  , Han Dan-Dan  ,   Mathematics and Physics School, University of Science and Technology Beijing, Beijing 100083, China;,   Institute of Software, Chinese Academy of Sciences, Beijing 100190, China
Published: December 2020

In the design of cryptographic algorithms, S-boxes provide the cryptosystems with the information confusion function. The traditional cryptography indexes of the S-boxes generally include linear deviation, differential characteristics, algebraic immunity, fixed point mumber, snowslide effect, and so on. In 2006, Kocarev et al. (Kocarev L, Szczepanski J, Amigo J M and Tomovski I 2006 IEEE Transactions on Circuits and Systems-I: regular papers 53 6 1300) set up a discrete chaos theory based on the finite set. In light of the theory in this paper, we introduce the definition of the Lyapunov exponent with Hamming distance, calculate and compare the Lyapunov exponent values of the S-boxes in several cryptographic algorithms. In this paper we prove that a map defined on the Euclidean distance has a maximal Lyapunov exponent value of 0. In this paper it is shown that the relationship between the Lyapunov exponent and the snowslide effect of the S-box is the relationship between the butterfly effect in chaos theory and the snowslide effect in cryptography. The definition of the Lyapunov exponent of the proposed S-boxes may be complementary to the traditional cryptography indexes of the S-box.
Detection of a coupled vibration by mechanical resonant absorption spectra
Authors: Yang Yue-Bin  , Zuo Wen-Long  , Bao Yan-Xiang  , Liu Shu-Yu  , Li Long-Fei  , Zhang Jin-Xiu  , Xiong Xiao-Min  ,   School of Information Science and Technology, Sun Yat-Sen University, Guangzhou 510006, China;,   State Key Laboratory of Optoelectronic Materials and Technologies, School of Physics and Engineering, Sun Yat-Sen University, Guangzhou 510275, China;,   Guangzhou East Campus Laboratory Center, Sun Yat-Sen University, Guangzhou 510006, China
Published: December 2020

In this paper, we propose a novel scheme of measuring a coupled but uneasy detected vibration mode through surveying another much easier detected vibration mode in a complex mechanical system. Through measuring the frequency dependence of phase lag of strain behind stress, i.e., the apparent mechanical dissipation-frequency spectrum, for the easy detected vibration mode, we are able to obtain the corresponding resonant absorption peak for the coupled vibration mode in addition to the expected main system resonance. By studying the observed resonant absorption peak: peak position, peak width and peak height, we can obtain the detailed information about the coupled vibration mode: the intrinsic resonant frequency, dissipation and coupling coefficient. Through measuring the apparent mechanical dissipation frequency spectrum of torsion vibration, the detection of the progression vibration about the pendulum axis is presented as a representative example of our scheme.
Study on spectroscopic properties of B2 (X3g-, A3u) molecule
Authors: Liu Hui  , Xing Wei  , Shi De-Heng  , Sun Jin-Feng  , Zhu Zun-Lue  ,   College of Physics and Electronic Engineering, Xinyang Normal University, Xinyang 464000, China;,   College of Physics and Information Engineering, Henan Normal University, Xinxiang 453007, China
Published: December 2020

The X3g- and A3u states of B2 molecule are studied using highly accurate valence internally contracted multireference configuration interaction approach including the Davidson modification. The Dunning's correlation-consistent basis sets, aug-cc-pV6Z and aug-cc-pV5Z, are used in the study. To obtain more reliable results, the potential energy curves (PECs) of two electronic states are extrapolated to the complete basis set limit by the two-point total-energy extrapolation scheme. The effects of the core-valence correlation and relativistic correction on PEC are taken into account. Employing these PECs, the spectroscopic parameters (Te, Re, e, exe, eye, Be, e, e and e) of the X3g- and A3u states of two main isotopes (11B2, 10B11B) are determined and compared with those reported in the literature. Comparison with the experimental data demonstrates that the present results are accurate. With the PECs determined here, the whole vibrational states for 11B2 (X3g-, A3u) and 10B11B (X3g-, A3u) are determined when the rotational quantum number J equals zero (J=0) by numerically solving the radical Schrdinger equation of nuclear motion. For each vibrational state of every isotope species, the vibrational level and inertial rotation constants are obtained, which are in excellent accordance with the experimental findings.
The nonsequential double ionization of argon atoms with elliptically polarized laser pulse
Authors: Yu Ben-Hai  , Li Ying-Bin  , Tang Qing-Bin  ,   College of Physics and Electronic Engineering, Xinyang Normal University, Xinyang 464000, China
Published: December 2020

With elliptically polarized laser pulse, the nonsequential double ionization (NSDI) of argon atoms is investigated using fully classical ensemble. The results show that the yield of NSDI decreases with increase of the ellipticity, that the momentum spectrum of the correlated electron from double ionization events in the final state shows a correlated behavior along the long axis of the laser polarization plane and an anticorrelated behavior along the short axis of the laser polarization plane, and that the momentum spectrum distribution of Ar2+ ion exhibits a single-peak structure at the zero along the short axis of the laser polarization plane, which becomes broader with the increase of the ellipticity. Trajectory back analyses show that the happening of NSDI is still due to recollision, and that the delay time between the collision and the single ionization increases with ellipticity increasing, which is because that the first electron needs more trips shuttling back and forth, so that it can recollide with the parent ion under the more ellipticity.
Effects of additional pulse wavelength at different frequencies on attosecond pulse generation in multicycle two-color laser field
Authors: Meng Jian  , Chen Gao  , Liu Sheng-Nan  ,   College of Science, Changchun University of Science and Technology, Changchun 130022, China
Published: December 2020

We theoretically investigate the effects of additional pulse wavelength at different frequencies on attosecond pulse generation from the hydrogen atom exposed to multicycle two-color laser field, by numerically solving the one-dimensional time-dependent Schrödinger equation. The results show that when the wavelength of the additional pulse is set to be 1600 nm, the cutoff position of the harmonic spectra is extended dramatically compared with the scenario in the case of 533 nm pulse in visible waveband, accordingly the bandwidth of supercontinuum is widened, finally 78 attosecond pulse is obtained by wavelet transform. In this paper, we explain the effects of additional pulse wavelength in different wavebands on high order harmonic generation for the first time according to the optical oscillation frequency of the synthesized field. Also, such a result is conducible to choosing the appropriate additional pulse frequency in order to obtain the isolated attosecond pulse.
Research on scattering properties of phosphor for high power white light emitting diode based on Mie scattering theory
Authors: Qian Ke-Yuan  , Ma Jun  , Fu Wei  , Luo Yi  ,   Graduate School at Shenzhen, Tsinghua University, Shenzhen 518055, China
Published: December 2020

Based on Mie scattering theory, the phosphor particle's scattering effect were simulated including light excitation and absorption. The light intensity proportion changes of forward and backward scattering light with different white light emitting diode (LED) color temperature were calculated. We also analyzed the phosphor particle size effecting the luminous flux of white LED and light color distribution of angle. Devices' excitation and emission spectrums used in our simulation were real measured spectrums of the material, rather than assuming a single spectrum. Our investigation discloses that when a conformal phosphor layer was adapted, phosphor particle diameter of 0.5 μm, makes maximum luminous flux and phosphor particles smaller, light color distribution of angel is better. While for given package structure, the best spatial color uniformity can be achieved with a phosphor layer thickness of 0.8 mm.
Scattering properties of non-spherical particles in the CO2 shortwave infrared band
Authors: Fan Meng  , Chen Liang-Fu  , Li Shen-Shen  , Tao Jin-Hua  , Su Lin  , Zou Ming-Min  , Zhang Ying  , Han Dong  ,   State Key Laboratory of Remote Sensing Science, Institute of Remote Sensing Application, Chinese Academy of Sciences, Beijing 100101, China;,   Graduate University of Chinese Academy of Sciences, Beijing 100049, China
Published: December 2020

Based on the T-matrix method and the generalized multiparticle Mie-solution (GMM) method combined with diffusion-limited aggregation simulator, the scattering properties of non-spherical particles and aggregates are simulated at 1.6 μm and 2.0 μm. And the effects of the equal-volume sphere radius, the complex refractive index, the particle shape and the relative humidity (RH) on the scattering characteristics parameters of non-spherical aerosol are analyzed. The results show that besides the equal-volume sphere radius and the particle shape, the RH could also lead to a large change of the scattering properties. And the relative differences in back scattering between spherical particles and non-spherical particles in different relative humidities are all larger than 18%. If the RH increases, the back scattering will increase for small-size particles, while the back scattering of large-size ones will decrease. The asymmetry factors of the smaller aggregates are 0.023 averagely greater than those of the single equal-volume non-spherical particles, which the asymmetry factors of the bigger aggregates are 0.055 averagely less than those of the single equal-volume non-spherical particles. The differences in single scattering albedo between the two wavelengths 1.6 μm and 2.0 μm are all much larger for either aggregates or single equal-volume particles, and the biggest difference reaches 0.226. This research has scientific significance for studying the aerosol multiple scattering influencing on the accuracy of CO2 satellite retrieval.
Fabry-Perot cavity locked by using single photon modulation
Authors: Wang Jing-Jing  , He Bo  , Yu Bo  , Liu Yan  , Wang Xiao-Bo  , Xiao Lian-Tuan  , Jia Suo-Tang  ,   State Key Laboratory of Quantum Optics and Quantum Optics Devices, Laser Spectroscopy Laboratory, Shanxi University, Taiyuan 030006, China
Published: December 2020

Fabry-Peort (FP) cavity-based quantum key distribution has some advantages in the phase-coded quantum key distribution (QKD). Locking the frequency of the FP cavity transmission to the frequency of single photon carrying the key information determines the security of QKD. In this paper, we propose an FP cavity locked to a single photon (the mean photon number is about 0.1) frequency using single-photon modulation/demodulation method. The single photon detector working in the Geiger mode is used to detect modulated single photons then direactly demodulated by the lock-in amplifier. The discrete single photon response pulses accumulated fulfills the phase sensitive detection, and the signal-to-noise ratio of signal frequency discrimination is up to 112. The transmission frequency fluctuation of the locked FP is limited to 2 MHz.