bluuebunny/crossref_metadata_2025 huggingface dataset:
Gate current degradation model of the AlGaAs/InGaAs PHEMT
Authors: Wan Ning  , Guo Chun-Sheng  , Zhang Yan-Feng  , Xiong Cong  , Ma Wei-Dong  , Shi Lei  , Li Rui  , Feng Shi-Wei  ,   College of Electronic Information and Control Engineering, Beijing University of technology, Beijing 100124, China
Published: December 2020

For quantitative study of time constant and degradation ratio of degradation parameters which correspond to different failure mechanisms in pseudomorphic high electron mobility transistor (PHEMT) gate current degradation process, a PHEMT gate current degradation model is established based on the relationship between reaction volume concentration and reaction rate in the process of degradation. The degradation law of PHEMT electrical parameters is obtained using online experiment method. The parameter degradation law with the time is analyzed and the failure mechanism which affects gate current degradation in different time period is obtained. Meanwhile, based on the gate current parameter degradation model, time constant and degradation ratio of degradation parameters, which correspond to different failure mechanisms, are also obtained.
Effect of doping concentration and doping thickness on the structure of electronic state of the Si uniformly doped GaAs quantum well
Authors: Yang Shuang-Bo  ,   School of Physical Science and Technology Nanjing Normal University, Nanjing 210046, China
Published: December 2020

By solving Schrodinger equation and Poisson equation self-consistently, we have calculated the electronic structure for Si-doped GaAs/AlGaAs quantum well system at T=0 in the effective mass approximation. We studied the influence of the doping concentration and the thickness of the doping layer on the subband energies, eigen-envelope functions, Hartree potential, density distribution of the electrons, and the Fermi energy. It is found that at the given doping concentration, the subband energies decrease with the increase of the doping thickness, the width of the self consistent potential well increase, the deepth of the well decrease, the distribution of the electron density becomes wider, the peak value reduced. At the given thickness of the doping layer, with the increase of the doping concentration, the subband energies and Fermi energy monotonically increase, the self consistent potential well becomes narrower and deeper, the peak of the electron density distribution becomes higher, and concentrated around the center of the well.
Electronic structure of twisted bilayer graphene
Authors: Wu Jiang-Bin  , Zhang Xin  , Tan Ping-Heng  , Feng Zhi-Hong  , Li Jia  ,   The State Key Laboratory of Superlattices and Microstructures, Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083, China;,   Science and Technology on ASIC Lab., Hebei Semiconductor Research Institute, Shijiazhuang 050051, China
Published: December 2020

This paper uses the first-principles and the tight-binding methods to study the electronic structures of twisted bilayer graphene for different angles. The band structures and density of states of twisted bilayer graphene in different angles are calculated. Our analysis points out that there is a linear dispersion relation in a twisted bilayer graphene, which is similar to a monolayer graphene, and the Fermi velocity of twisted graphene is lower and lower with reducing angle. Furthermore, gaps appearing at M point of certain angles, in which the width of gap depends on the twist angle, this gap would strengthen the Raman mode intensity of twisted bilayer graphene, as was confirmed by experiment. The comparison of moire patterns and the location of density of states both certify that AB region of moire patterns is the reason of gap at M point.
Nanowires array designed by means of two-dimension closed-form solution for antireflection
Authors: Zhu Zhao-Ping  , Qin Yi-Qiang  ,   College of Engineering and Applied sciences, PV Engineering Research Center, National Laboratory of Solid State Microstructures, Nanjing University, Nanjing 210093, China
Published: December 2020

By investigating the difference between the analytic solutions obtained from commonly used two-dimensional effective medium theory and the numerical solutions, we found that any analytical solution was quite accurate only at its right normalized cycle, determined by its own effective range. Thus, one should solve the problem that there was no closed-form solution for the effective permittivity of a two-dimensional zero-order grating, and expand the applied scope of the effective medium theory to the boundary of zero-order diffraction. Secondly, by using the two-dimensional analytical solution, we have designed a nanowires anti-reflection layer in silicon, which fully meet the needs of the design that reach zero reflectance at 650 nm; and the spectrum averaged reflection from 310-1120 nm is 8%, lower than silicon nitride anti-reflection layer 9.9%. Stavenga formula can be used to design a large normalized period antireflective microstructure, while the Maxwell-Garnett formula can be used to design a small normalized cycle antireflective microstructure. Design of antireflection structure by two-dimensional closed form solution directly is viable, which have huge potential application value.
Effect of Li+ and Er3+ co-doping on the luminescence properties of Ba2SiO4：Eu
Authors: Luo Lin-Ling  , Tang Ke  , Zhu Da-Chuan  , Han Tao  , Zhao Cong  ,   College of Materials Science and Engineering, Sichuan University, Chengdu 610065, China;,   Chengdu University of Technology, College of Geophysics, Chengdu 610059, China;,   Research Center for Material Interdisciplinary Science, Chongqing University of Arts and Sciences, Chongqing 402168, China
Published: December 2020

A series of Ba1.99-x/2-2ySiO4:Eu0.012+, Lix+y2+, Euy3+ green phosphors were synthesized by one-step calcination process with precursor prepared by chemical precipitation. X-ray diffraction (XRD) and fluorescence spectrophotometry were employed to characterize the crystal structure and luminescent properties, respectively. The results show that co-doping of Eu2+, Li+ or Er3+ do not change the crystal structure. The excitation band of green phosphors Ba1.99-x/2-2ySiO4:Eu0.012+, Lix+y2+, Euy3+ extends from 270 to 440 nm, with peaks appearing around 288 and 360 nm, thus the phosphors can be excited effectively by InGaN chip which produces ultraviolet light in the range of 350410 nm. The emission spectrum excited by 360 nm shows a characteristic wide band with a peak at about 500 nm, which can be attributed to the typical 4f65d14f7 transition emission of Eu2+. The emission spectrum intensity of Ba1.99-x/2SiO4:Eu0.012+, Lix2+ first increases with increasing Li+ doping concentration, and then decreases. The strongest emission intensity occars when Li+ doping concentration is 0.1. Two additional peaks appear in the emission spectrum of Ba1.99-x/2-2ySiO4:Eu0.012+, Lix+y2+, Euy3+ green phosphors around 488 nm and 530~nm separately when the phosphors are co-doped with Li+ and Er3+ from 0 to 0.012, which are attributed to the 4F7/24I15/2 and 2H11/24I15/2 translation emission of Er3+, the energy transfer effect from Eu2+ to Er3+ is also analyzed.
Microstructural and photoelectrical properties of oxygen-ion-implanted microcrystalline diamond films
Authors: Wang Feng-Hao  , Hu Xiao-Jun  ,   College of Chemical Engineering and Material Science, Zhejiang University of Technology, Hangzhou 310014, China
Published: December 2020

The influences of oxygen ion dose and annealing temperature on the microstructural and photoelectrical properties of microcrystalline diamond films with Si-V luminescence centers were systematically investigated. Results show that high temperature annealing prefers to increase the Si-V luminescence intensity in oxygen-ion-implanted microcrystalline diamond films. With oxygen ion dose increasing from 1014 to 1015 cm-2, the Si-V luminescence intensity of the films enhances. Hall effects measurement show that the resistivity of the films becomes lower after annealing. At different annealing temperatures, the oxygen-ion-implanted microcrystalline diamond films with stronger Si-V luminescence intensity exhibit larger resistivity, indicating that the Si-V luminescence centers are not favorable to the enhance ment of the conductivity of films. Results of Raman spectroscopy show that the increase of defects in films will enhance Si-V luminescence intensity and decrease the conductivity of the films.
Optoelectrical properties of tantalum-doped TiO2 thin films
Authors: Xue Jiang  , Pan Feng-Ming  , Pei Yu  ,   Department of Applied Physics, College of Science, Nanjing University of Aeronautics and Astronautics, Nanjing 211100, China
Published: December 2020

Tantalum-doped TiO2 thin films were deposited on glass substrates by pulsed laser deposition (PLD). Their optoelectrical properties were studied. The optical band gap was found varying between 3.26 and 3.49 eV when the oxygen partial pressure increases from 0.3 to 0.7 Pa. The dependence of electrical property of the films on temperature was measured to identify the dominant conduction mechanism. It was found that thermally activated band conduction was the dominant conduction mechanism in the temperatures range of 150 to 210 K. Whereas, in the temperature region of 10 to 150 K, the dependence of the conductivity on temperature followed Mott’s variable range hopping (VRH) model. Moreover, the temperature dependence of resistivity for the films can be described by～ exp(b/T)1/2 at temperatures from 210 to 300 K.
Self-consistent field simulation of hierarchical self-assembly structures from AB/CD block copolymer blends
Authors: Fan Juan-Juan  , Yu Xiu-Ling  , Liang Xue-Mei  ,   College of Information Technology, Jilin Agricultural University, Changchun 130118, China
Published: December 2020

Using the self-consistent mean field theory, we have studied the self-assembly behavior of AB/CD block copolymers blend. Simulation results show that the hierarchical structural transitions from lamellar structures on different spatial scales to core-shell structure were caused by the increase of the fusion degree between components B and D. When the mutual fusion degrees between components B and D, between A and B, and between C and D are equal, the structure will change from macro-lamellar to micro-lamellar. In addition, the variation of free energy with the interaction between B and D were also calculated to deepen the understanding about the structural transition.
Influence of aging time on mechanical properties and microstructures of FeNiAlTa shape memory alloy
Authors: Yang Neng-Wu  , Peng Wen-Yi  , Yan Ming-Ming  , Wang Wei-Wei  , Shi Hai-Ping  ,   School of Materials Science and Engineering, Nanchang University, Nanchang 330031, China
Published: December 2020

This paper focuses on the Fe59.5Ni28Al11.5Ta1 memory alloy, in which the effects of different aging treatments on microstructure and properties of the rolled alloy are investigated by metallurgical microscope, X-ray diffraction, SEM, EDS and pressure test machine. Results show that, because of aging treatment, precipitation of γ’ and β’ phase strengthens the austenitic matrix. With the increase of aging time at 600 ℃, the comprehensive analysis of pseudoelasticity curve, shows that the stress-induced martensite critical stress of the aging state of the alloy decreases first and then increases; the alloy compressive strength, the recoverable strain and the hardness increase first and then decrease, Besides, the alloy residual strain is first decreased and then increased. When the aging time is 60 h, the alloy compressive strength is the maximum, up to 1306 MPa, the alloy recoverable deformation is the maximum, reaching 14.9%, the hardness of the alloy is also the largest, but the alloy residual strain is relative minimum. With the increase of aging time, alloy maximum strain decreases gradually, and the plasticity of the alloy also decreases gradually. The properties of the shape memory alloy are influenced by the particle size, its distribution, volume fraction, of precipitate phase etc.
Estimation of temperature distribution of the polymer lithium ion power battery based on the coupling relationship between electrochemistry and heat
Authors: Tang Yi-Wei  , Jia Ming  , Cheng Yun  , Zhang Kai  , Zhang Hong-Liang  , Li Jie  ,   School of Metallurgy Science and Engineering, Central South University, Changsha 410083, China;,   Engineering Research Center of High Performance Battery Materials and Devices in Shenzhen, Research Institute of Central South University in Shenzhen, Shenzhen 518057, China
Published: December 2020

To understand the thermal effect of polymer Li-ion cells during the discharge process, an electrochemical thermal coupling model was established to investigate the thermal behavior of the cell. The average deviation and variance between the modeling results and the experimental data at 3C discharge rate were 0.57 K and 0.15, thus it was concluded that the modeling results agreed well with the experimental data. Also, the model is used to analyze the temperature distribution affected by discharge rate and cooling condition. The average heat production rate of the cells shows an increasing trend throughout the discharge process; it is increased significantly at both the beginning and the end of discharge. At a high discharge current, the irreversible heating which is proportional to the square of the current density, is the major heat generation source inside the battery. At a low discharge current, the heat production rate is dominated by reversible entropic heat. Improving cooling temperature could lower the average temperature during the discharge process. When the heat coefficient is 5 W/(m2·K), the average temperature rises of the battery cells are 6.46 K, 17.67 K, 27.53 K for 1C, 3C, 5C discharge rates respectively. If the heat coefficient increases to 25 W/(m2·K), the average temperatures of the battery cells are reduced by 2.91 K, 4.68 K, 5.62 K for 1C, 3C, 5C discharge rates, respectively, but the inner temperature difference would be increased.
A novel meminductor emulator based on analog circuits
Authors: Liang Yan  , Yu Dong-Sheng  , Chen Hao  ,   The School of Information and Electrical Engineering, China University of Mining and Technology, Xuzhou 221116, China
Published: December 2020

Meminductor, a nonlinear device with memory ability and controllable meminductance, was generalized on the basis of the conception of memristor. Currently, meminductor is still unavailable on the market. Therefore, in order to investigate its properties and potential application, designing electronic emulator is of significant importance. In this paper, a flux-controlled memristive emulator using ligh-dependent resistor (LDR) is proposed and the mutator for transferring memristor into a flux controlled meminductor is described, of which the realization is on the basis of two current conveyor chips and operational amplifiers. Results of Pspice simulation and hardware experiments indicate that the current-flux characteristic of the meminductor is a frequency-dependent pinched loop, like an inclined number “8”. To confirm the effectiveness and correctness, the proposed emulator is analyzed theoretically and tested experimentally as it is connected in an RLMC series circuit. The dynamic behaviors of the RLMC circuit are analyzed and observed. All the results manifest that this newly proposed emulator is capable of simulating a nonlinear meminductor and can be applied to the analog circuit design.
Two-dimensional analytical model of dual material gate strained Si SOI MOSFET with asymmetric Halo
Authors: Xin Yan-Hui  , Liu Hong-Xia  , Fan Xiao-Jiao  , Zhuo Qing-Qing  ,   Key Laboratory for Wide Band Gap Semiconductor Materials and Devices of Education, School of Microelectronics, Xidian University, Xi’an 710071, China
Published: December 2020

In order to improve the driving current and suppress the SCE and DIBL effect of deep submicron SOI MOSFET, dual material gate strained Si SOI MOSFET structure with asymmetric Halo has been proposed. An impurity with a higher concentration is injected into the channel end near the source and the two materials with different work functions are put together to form the gate. By considering both the characteristics of the new device structure and the influence of strain, the flatband voltage and built-in potential have been corrected. A two-dimensional analytical model for the surface potential and the threshold voltage is proposed by solving Poisson’s equation. The effect of Ge fractions in the relaxed layer on surface potential, surface electric field, and threshold voltage is investigated. The model proposed in this paper takes into account the effects of gate metals length and their work functions. Results show that the novel device can increase carrier transport speed and suppress the SCE and DIBL effects, which provides a valuable reference to the physical parameter design.
Application of amplitude and phase registration in blood flow imaging using optical coherence tomography
Authors: Liu Guo-Zhong  , Zhou Zhe-Hai  , Qiu Jun  , Wang Xiao-Fei  , Liu Gui-Li  , Wang Rui-Kang  ,   School of Instrument Science and Opto-Electronics Engineering, Beijing Information Science and Technology University, Beijing 100192, China;,   School of Applied Science, Beijing Information Science and Technology University, Beijing 100192, China;,   Department of Bioengineering, University of Washington, Seattle 98195, USA
Published: December 2020

The amplitude and phase fluctuations of A-scans, influenced by the galvanometer positioning accuracy, mechanical jitter, and especially the ovement of the sample, may lead to the distortion and degradation of the tissue structure images and the blood flow images within tissue beds in frequency domain optical coherence tomography. The amplitude registration method for A-scans is proposed based on the minimum intensity difference matching criterion, Lorentzian curve fitting method, and compensation of the optical path difference in interference spectrum. The phase differences between A-scans are detected and registered by matching of phase distribution characteristics of A-scans. After the amplitude and phase registration, the complex signal differences between two A-scans are calculated to eliminate the effect of the static tissue on the blood flow imaging. The eye scanning experiments were performed and three-dimensional blood flow images of retina were acquired. Experiment results indicate that the effect of system scanning accuracy and tissue movement on the image quality can be effectively eliminated by the proposed amplitude and phase registration method. The fast and accurate phase registration method can also be used in Doppler OCT, phase microscope, and other phase related applications.
Synthesis of CNT film on Cu and its intense pulsed emission characteristics
Authors: Ma Hua-Li  , Huo Hai-Bo  , Zeng Fan-Guang  , Xiang Fei  , Wang Gan-Ping  ,   Department of Mathematics and Physics, Zhengzhou Institute of Aeronautical Industry Management, Zhengzhou 450015, China;,   Science and Technology on High Power Microwave Laboratory, Institute of Applied Electronics, CAEP, Mianyang 621900, China
Published: December 2020

In order to study intense pulsed emission characteristics of carbon nanotube films (CNTs), CNTs were synthesized on the surface of Cu substrate (Cu-CNTs) by pyrolysis of iron phthalocyanine (FePc). Orientations of CNTs obtained are different from one another. Intense pulsed field emission of CNTs was measured on the 20GW pulse power system using a diode structure. For single pulse emission, the emission current peak of Cu-CNTs increases linearly with pulse field peak, at the applied peak electric field of ～15.5 V/μ; the current peak is ～5.56 kA, and equivalent emission current density is ～0.283 kA/cm2. At the applied peak electric field of ～32.0 V/μ, the current peak can achieve ～18.19kA, and the equivalent emission current density is～0.927 kA/cm2; the ability of emission current of CNTs is obviously better than that reported. In many continuous and similar peak pulse emissions, Cu-CNTs provide with good repeatability of pulsed emission, and present better emission stability.
The periodic modulation of a Bose-Fermi mixture in double-well trap
Authors: Zhang Heng  , Duan Wen-Shan  ,   College of Physics and Electronic Engineering, Northwest Normal University, Lanzhou 730070, China
Published: December 2020

In this paper, we study the self-trapping of a Bose-Fermi mixture in a periodic modulation field by adjusting fermionic number and interaction parameter in a double-well potential. We find that the self-trapping of bosons can be affected by interatomic self-interaction and interspecific interaction parameter. Moreover, we notice that the self-trapping of bosons gives rise to a critical phenomenon with the variation of interaction strength and fermionic number.
Dynamics of current controlled quadratic boost converters
Authors: Yang Ping  , Xu Jian-Ping  , He Sheng-Zhong  , Bao Bo-Cheng  ,   Key Laboratory of Magnetic Suspension Technology and Maglev Vehicle, Ministry of Education, School of Electrical Engineering, Southwest Jiaotong University, Chengdu 610031, China;,   School of Information Science and Engineering, Changzhou University, Changzhou 213164, China
Published: December 2020

The two inductor current boundaries are derived, and segmented smooth iteration mapping model of current controlled quadratic boost converter is established based on the detailed description of switching states. The comparative analyses of the nonlinear bifurcation behaviors are performed with input inductor current and the storage inductor current as current feedback respectively. Two boundary conditions for the transition from stable period-one state to sub-harmonic oscillation state and for the transition from discontinuous conduction mode to continuous conduction mode are derived by analyzing stability and operation mode. The operation-state regions corresponding to circuit parameter regions are estimated by utilizing the parameter-space maps. An experimental circuit is built and the results show that both different bifurcation routes and operation mode transition phenomenon are changed with parameter variation, the current controlled quadratic boost converter exhibits complicated dynamical behaviors. The experimental results verify the correctness of the theoretical analysis.
Effect of apparatus polarization efficiency on quantification analysis in polarized neutron imaging
Authors: Cao Chao  , Li Hang  , Huo He-Yong  , Tang Ke  , Sun Yong  ,   Insitute of Nuclear Physics and Chemistry, China Academy of Engineering Physics, Mianyang 621900, China
Published: December 2020

Polarized neutron radiography allows the direct and real-space visualization of magnetic field distribution by detecting the polarization change in the transmitted beam. Spin polarizer/analyzer apparatus is important in polarized neutron imaging system, whose polarization efficiency directly affects the imaging quality of magnetic field. In this paper, the relation between the registered neutron intensity and magnetic field distribution is re-calculated after introducing the polarization efficiency parameter. Bender polarizers and 3He spin filters are simulated by Monte Carlo software VITESS to verify the calculation. The quantification ability with low beam polarization is also analyzed by considering the beam monochromaticity and bender geometry. The results will be helpful for processing image data and designing instrument.
First-principles study on the electronic structure and optical properties of RDX
Authors: Cheng He-Ping  , Dan Jia-Kun  , Huang Zhi-Meng  , Peng Hui  , Chen Guang-Hua  ,   Institute of Fluid Physics, China Academy of Engineering Physics, Miangyang 621900, China;,   Institute of Applied Physics, School of Mechanical Electronic and Information Engineering, Huangshan University, Huangshan 245041, China;,   State Key Laboratory of Explosion and Technology, Beijing Institute of Technology, Beijing 100081, China
Published: December 2020

Electronic structure and optical properties of RDX are calculated by the first-principle density function theory pseudopotential method. The calculated results show that RDX is an insulator with a band gap of 3.43 eV, that the valence band of RDX is mainly composed of C-2s, C-2p, N-2s, N-2p and O-2s, O-2p, and that the conduction bands are mainly composed of N-2p and O-2p. The static dielectric function ε1(0) is 1.38, the imaginary part of dielectric function has five peaks and the largest peak is at the position corresponding to 4.6 eV of photon energy. The electronic direct transitions for these peaks are analyzed in detail. The absorption, reflectivity and loss function of RDX are analyzed in terms of calculated band structure and density of states. The results indicate that the RDX is not sensitive to the optical absorption nor to reflectivity nor to energy loss.
Resolution of coherent field imaging technique
Authors: Zhang Wen-Xi  , Xiang Li-Bin  , Kong Xin-Xin  , Li Yang  , Wu Zhou  , Zhou Zhi-Sheng  ,   Academy of Optics and Electronics, Chinese Academy of Sciences, Beijing 100094, China;,   University of Chinese Academy of Sciences, Beijing 100049, China;,   Department of Precision Machinery and Precision Instrumentation, University of Science and Technology, Hefei 230027, China
Published: December 2020

According to the relevant theory of optical transfer function (OTF), the OTF and point spread function of coherent field imaging technology (also known as Fourier telescopy) are derived. The formulas for calculating the resolution power of coherent field imaging system with T type and O type transmitter arrangement are given, which provides a theoretic basis of analyzing the limited angle resolution of coherent field imaging system. Based on this study, the relationship between resolutions of the coherent field imaging system with T type and O type transmitter arrangement is investigated.
Polarization properties of plasmonic color filters comprised of arrays of subwavelength size holes on Au films
Authors: Wang Pei-Pei  , Yang Chao-Jie  , Li Jie  , Tang Peng  , Lin Feng  , Zhu Xing  ,   State Key Laboratory for Mesoscopic Physics, School of Physics, Peking University, Beijing 100871, China;,   National Center for Nanoscience and Nanotechnology, Beijing 100190, China
Published: December 2020

Plasmonic color filters comprised of metal films can be adjusted easily. Periodic arrays of subwavelength size holes with circle, square and rectangular shape are fabricated on 200 nm thick Au films by using focused ion beam. The structures are utilized as plasmonic color filters for exhibiting color variation under the illumination of white light in different polarization directions. We find that for rectangular hole arrays, the color of the transmitted light changes greatly with polarization direction. However, for arrays of circle and square holes, color of the transmitted light is not sensitive to the polarization direction of incident light. We conclude that localized surface plasmon around a single hole is a key factor in influencing the color of transmission light, rather than surface plasmon polaritons induced by periodic arrays. If incident light does not excite the localized surface plasmon around the holes, the effect of surface plasmon polariton will disappear, Based on different display colors of transmitted light of the subwavelength holes with polarization, a composite color display sample is prepared, which will exhibit different color patterns as the polarization direction of incident light changes.
Design and study of the active frequency selective surface based on the complementary screen
Authors: Jiao Jian  , Xu Nian-Xi  , Feng Xiao-Guo  , Liang Feng-Chao  , Zhao Jing-Li  , Gao Jin-Song  ,   Key Laboratory of Optical System Advanced Manufacturing Technology, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, Changchun 130033, China;,   University of Chinese Academy of Sciences, Beijing 100049, China
Published: December 2020

Separating the load impedance of the resonant frequency selective surface (FSS) can form the complementary frequency selective surface (CFSS), whose filtering feature is based on the coupling mechanism. The resonance of CFSS can be tuned by controlling the rotation angle of the element on the capacitive surface. Taking tripole element for example, the frequency response of the CFSS is calculated by using the coupled integral equation method. A 250 mm250 mm prototype is tested via free space method. Calculation and test results show that the resonance of the CFSS can be tuned actively as the rotation angle changes. This study provides reference to the active FSS design.
Gaussian type inhomogeneous stress and strain effects on the magnetic properties in ferromagnetic thin films
Authors: Zhu Jie  , Su Yuan-Chang  , Pan Jing  , Feng Guo-Lin  ,   College of Physics Science and Technology, Yangzhou University, Yangzhou 225002, China
Published: December 2020

The effects of Gaussian type inhomogeneous stress and strain on the magnetic properties in ferromagnetic thin films are studied by Monte-Carlo simulation. The results show that the coercive field could be enhanced by the strain parallel to the easy axis and stress perpendicular to the easy axis, on the other hand, it could also be weakened by the stress parallel to the easy axis and strain perpendicular to the easy axis. The coercive field increases (or decreases) in the system, meanwhile, the remanent magnetization and squareness increase (or decrease) as well. More interestingly, the easy axis will rotate within the centralized region under stress parallel to the initial easy axis and strain perpendicular to the initial easy axis. The range of centralized region with easy axis rotation is strongly dependent on the magnitude of stress or strain and the width of its distribution.
Piezoelectric and acoustic behavior of polypropylene piezoelectret films
Authors: Zhang Xin-Wu  , Zhang Xiao-Qing  ,   Shanghai Key Laboratory of Special Artificial Microstructure Materials and Technology, School of Physics Science and Engineering Tongji University, Shanghai 200092, China
Published: December 2020

Piezoelectrets are made from cellular polypropylene(pp)foam sheets by using a pressed-gas expansion followed by corona charging process. The elastic modulus, piezoelectricity and the acoustic response of such fabricated films are investigated. The results show that the Youngs modulus in the thickness direction is more than two orders of magnitude higher than those in the transverse directions. The d33 coefficient remains linear in an applied pressure range from 15 to 35 kPa. As measuring frequency increases from 2 to 300 Hz, d33 coefficient decreases to 81%, which is probably associated with the enhancement of elastic modulus of the film with pressure increasing. In a range from 100 Hz to 100 kHz, the PP piezoelectric films exhibit flat frequency response curves. The open circuit voltage sensitivity and d33 coefficient at 1 kHz are 0.84 mV/Pa and 164 pC/N, respectively.
Epidemic spreading on multi-relational networks
Authors: Li Rui-Qi  , Tang Ming  , Hui Pak-Ming  ,   Web Science Center, University of Electronic Science and Technology of China, Chengdu 610054, China;,   Department of Physics, The Chinese University of Hong Kong, Hong Kong, China
Published: December 2020

Networks with links representing different relationships have attracted much attention in recent years. Previous studies mostly focused on the analyses of network topology and evolution, multi-relation pattern mining, detection of overlapping communities, and cascading failure. However, epidemic spreading on multi-relation networks remains a largely unexplored area. We propose a binary-relation network model, representing working and friendship relationships, to reveal the effect of multiple relationships on the epidemic spreading. A link representing a closer relationship carries a higher weight. For reactive infection process in a multi-relation network, the threshold of outbreak is suppressed, making the epidemic harder to control. Comparing the networks with different structural heterogeneities such as the Watts-Strogatz (WS), Erdös-Rènyi and Barabási-Albert networks, the WS network is affected most significantly. Interestingly, the relative changes in the thresholds on the three networks are found to be independent of the structure. For contact infection process, an increase in the weight of the closer relationship can raise the outbreak threshold significantly and reduce the prevalence. As the fraction of closer relationship varies, an optimal fraction corresponding to a maximum outbreak threshold and minimum prevalence emerges. With an increase in the weight of the closer relationship, the proportion of links corresponding to the optimal value decreases. Most interestingly, the optimal proportions of closer-relation links on the three networks are almost the same, and thus they are independent of the network topology. This study not only contributes to the better understanding of epidemic spreading dynamics on multi-relation networks, but also provides a new perspective for research on multi-relation networks.
Realization of synchronization between hyperchaotic systems by using a scheme of intermittent linear coupling
Authors: Ma Jun  , Wu Xin-Yi  , Qin Hui-Xin  ,   Department of Physics, Lanzhou University of Technology, Lanzhou 730050, China
Published: December 2020

Based on the Lyapunov stability theory, it is confirmed that complete synchronization can be realized under intermittent linear coupling. The linear controller is selected as ‘stop’ or ‘on control’ by using a switch function; while the first switch function is realized by using a rectangular wave with the same amplitude, and the controller turns on/off in the peiod Ta, Tb alternately. The second switch function is adjusted by a square wave with the same amplitude, and the interval period is marked as T0. At first, a class of exponential Lyapunov function is designed to discuss the reliability and possibility of complete synchronization induced by indirectional linear coupling when the controller is adjusted by two types of switch function. The averaged power consumption of controller within a transient period is defined to measure the cost and efficiency of this scheme. In numerical studies, for the case of first switch function (rectangular wave), the distribution of the largest conditional Lyapunov function for the response system is calculated in the two-parameter space for interval period Ta vs. Tb, the synchronization area vs. nonsynchronization area, the distribution of averaged power consumption in the parameter space Ta vs. Tb. It is also confirmed that complete synchronization can be reached at appropriate Ta, Tb, and coupling intensity. In the case of the second switch function, the distribution of the largest conditional Lyapunov function for the response system is calculated in the two-parameter space for coupling intensity k vs. interval period T0, and the series of error function and averaged power consumption. It is found that complete synchronization can be realized at appropriate coupling intensity and interval period T0. It is also found that the averaged power consumption of controller within a transient period can reach a smallest value at an appropriate coupling intensity. Numerical results are consistent with the theoretical analysis.
Arbitrary and absolute length measurement based on femtosecond optical frequency comb
Authors: Xing Shu-Jian  , Zhang Fu-Min  , Cao Shi-Ying  , Wang Gao-Wen  , Qu Xing-Hua  ,   State Key Laboratory of Precision Measurement Technology and Instruments, Tianjin University, Tianjin 300072, China;,   Division of Time and Frequency MetrologyNational Institute of Metrology, Beijing 100013, China;,   State Key Lab of Applied Optics, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, Changchun 130033, China
Published: December 2020

High-accuracy distance measurement plays an important role in many applications, such as industry measurement, Aerospace and scientific research. The continual development oflaser ranging technique is always a frontier topic of geometric measurement, therefore this paper develops the application of femtosecond optical frequency comb for length measurement. Time-of-flight principle for distance measurement is widely used by pulse laser, however, achievable resolution reaches only a few millimeters at best due to the limited bandwidth of electronics. In this paper, the temporal coherence of multiple pulse train is analyzed, and an arbitrary and absolute length measurement system is set up based on modified Michelson interferometer by combining multiple pulse train interference and time-of-flight method. The timing difference is separately calculated by the first-order and second-order optical cross-correlation signals, therefore the absolute distance is calculated. An experiment is conducted by measuring a 60 cm length, and the measurement result is compared with a high precision laser displacement sensor. The result shows a good measuring linearity, and the measurement precision of ±0.5 μm is achieved.
Investigation on large-mode-area flat-topped optical fiber with microstructured core and its transmission characteristics
Authors: Zhang Yin  , Chen Ming-Yang  , Zhou Jun  , Zhang Yong-Kang  ,   School of Mechanical Engineering, Jiangsu University, Zhenjiang 212013, China;,   Faculty of Science, Ningbo University, Ningbo 315211, China;,   School of Mechanical Engineering, Southeast University, Nanjing 211189, China
Published: December 2020

A novel microstructured-core optical fiber with large mode area and flat-topped mode field distribution is proposed. The core of the fiber is composed of high refractive index dielectric cylinders with a non-uniform distribution. Numerical simulation on the mode area, mode field distribution of the fundamental mode and other aspects of the fiber indicates that the fiber can effectively obtain flat-topped mode field distribution by tuning the parameters of the cladding and the core of the fiber. In addition, the flat-topped fiber has a large mode area of 1655 μm2 at the operating wavelength of 1064 nm.
Investigation on characteristics of flow in microchannels with random surface roughness
Authors: Yan Han  , Zhang Wen-Ming  , Hu Kai-Ming  , Liu Yan  , Meng Guang  ,   State Key Laboratory of Mechanical System and Vibration, Shanghai Jiao Tong University, Shanghai 200240, China
Published: December 2020

We have investigated the characteristics of gas flow in microchannels under the coupled effects of random surface roughness and velocity slip by the method of computational fluid dynamics. The random surface roughness is modeled by fractal geometry, and the velocity slip on boundary is described by second-order slip law. Results show that the simulated curves obtained by considering both second-order slip law and random surface roughness are in good agreement with experimental data in a range of averaged Knudsen number from 0.025 to 0.59, while the one gained by using Maxwell slip law are in agreement with experimental data in a range of averaged Knudsen number extending up to 0.1. Random surface roughness has an obvious effect on velocity slip: as relative surface roughness increases, velocity slip coefficients decrease. An approximate relation between relative surface roughness and velocity slip coefficients is given according to the results. Last but not least, random surface roughness has a significant effect on the pressure, velocity and Poiseuille number.
Stability of liquid droplet containing insoluble surfactant spreading over corrugated topography
Authors: Li Chun-Xi  , Pei Jian-Jun  , Ye Xue-Min  ,   Key Laboratory of Condition Monitoring and Control for Power Plant Equipment, North China Electric Power University, Baoding 071003, China
Published: December 2020

For the spreading of an insoluble surfactant-laden droplet over the corrugated topography, the lubrication theory is used to establish the physical and mathematical models of the spreading of droplet and to derive the base state and disturbance evolution equations for thin liquid film thickness and surfactant concentration. The stability of droplet spreading on topography surfaces, as well as the effects of several parameters are investigated based on the non-model stability theory. Results show that disturbance quantities reach minimum at the droplet center and spreading fronts, and achieve the maximum in thinning regions, and the negative disturbance of surfactant concentration is quite obvious. Disturbance wave number can enhance the stability of the droplet spreading, but with increasing wave number, the stability tends to be weak and even transform into instability. The spreading stability is distinctly promoted with decreasing Marangoni number or increasing corrugated topography height. The droplet evolution displays a much stable spreading for moderate values of Peclet number and topography wave number.
Exchange bias effect in single crystalline phase MnO nanoparticles
Authors: Luo Yi  , Zhao Guo-Ping  , Yang Hai-Tao  , Song Ning-Ning  , Ren Xiao  , Ding Hao-Feng  , Cheng Zhao-Hua  ,   College of Physics and Electronic Engineering, Sichuan Normal University, Chengdu 610068, China;,   State Key Laboratory of Magnetism, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
Published: December 2020

The MnO nanoparticles with uniform size (～15 nm) and shape have been synthesized in an inert atmosphers by high-temperature oil phase method. XRD patterns and HRTEM reveals that the as-synthesized MnO nanoparticles are of pure crystalline phase. TEM image shows that the MnO nanoparticles are in spherical shape with a narrow size distribution. Both oil phase and the nanoparticles protected with inert gas in the synthesis process can avoid the oxidization of Mn2+. The obvious exchange bias effect can be observed from the M-H loop of MnO nanoparticles under zero field cooling (ZFC) and FC measurements. Furthermore, the temperature-dependent AC susceptibility of the MnO nanoparticles reveals that the exchange bias effect originates from the antiferromagnetic MnO core and the spin-glass surface, rather than the superparamagnetic phase.
Molecular dynamics simulation of tensile deformation mechanism of the single crystal tungsten nanowire
Authors: Ma Bin  , Rao Qiu-Hua  , He Yue-Hui  , Wang Shi-Liang  ,   School of Civil Engineering, Central South University, Changsha 410075, China;,   State Key laboratory of Powder Metallurgy, Central South University, Changsha 410083, China
Published: December 2020

Molecular dynamics method was used to simulate tensile deformation of the high-purity single-crystal tungsten nanowire prepared by the metal-catalyzed vapor-phase reaction method first proposed by our research group. Stress-strain curve and microscopic deformation structure were analyzed in order to reveal the tensile deformation characteristics and microscopic failure mechanism of the single-crystal tungsten nanowire. Results show that the whole stress-strain curve can be classified into five stages: elastic stage, damage stage, phase transition stage, hardening stage and failure stage, where the phase transition is the main reason for hardening of the single-crystal tungsten nanowire. The first stress drop is caused by irreversible change of the local atomic dislocation and twinning, and the second stress drop is due to lattice structure failure resulting from the local atomic dislocation of the strengthened material and the development of split-forming necking area leading to the fracture of single-crystal tungsten nanowires. Calculated result of the elastic modulus is in good agreement with the test results of elastic modulus of the single-crystal tungsten nanowire.
First principles studies of phase transition and mechanical properties of uranium
Authors: Liu Ben-Qiong  , Xie Lei  , Duan Xiao-Xi  , Sun Guang-Ai  , Chen Bo  , Song Jian-Ming  , Liu Yao-Guang  , Wang Xiao-Lin  ,   Institute of Nuclear Physics and Chemistry, China Academy of Engineering Physics, Mianyang 621900, China;,   Research Center of Laser Fusion, China Academy of Engineering Physics, Mianyang 621900, China
Published: December 2020

Using density functional theory, the structural parameters of α-U and bcc phases were obtained separately, in reasonable agreement with previous experimental and theoretical results. The enthalpy-pressure curve showed that the phase transition pressure was approximately 111 GPa. The structural behavior of γ-U under extreme loading conditions was exhibited by the ideal strength calculations. In addition, by analyzing the energy-strain relationship we found that the strain corresponding to the shear modulus c’ could decrease the total energy of U-Nb (6.25 at.%) alloy, indicating the instability of this structure.
Single event effect of 3D H-gate SOI NMOS devices in total dose ionizing
Authors: Zhuo Qing-Qing  , Liu Hong-Xia  , Wang Zhi  ,   Key Laboratory for Wide Band Gap Semiconductor Materials and Devices of Ministry of Education, School of Microelectronics, Xidian, University, Xi’an 710071, China
Published: December 2020

The single event effect of H-gate SOI NMOS devices in total dose ionizing are studied by means of numerical simulation. By analyzing the mobility degradation in the simulation process, the corrected mobility Lombardi model due to degradation at interfaces is obtained. As the simulated transfer characteristic curves of SOI transistor agree well with the experimental data, the single event effect of H-gate SOI NMOS devices in total dose ionizing is simulated by this corrected model. Results shows that the maximum drain currents of devices under the same conditions are slight increasing, but the transistors get a significant increase in the drain collected charge with increasing total dose level.
Numerical investigation of bubble nucleation process using the lattice Boltzmann method
Authors: Zeng Jian-Bang  , Li Long-Jian  , Jiang Fang-Ming  ,   Laboratory of Advanced Energy Systems, CAS Key Laboratory of Renewable Energy, Guangzhou Institute of Energy Conversion, Chinese Academy of Sciences, Guangzhou 510640, China;,   Key Laboratory of Low-grade Energy Utilization Technologies and Systems of Ministry of Education, College of Power Engineering, Chongqing University, Chongqing 400030, China
Published: December 2020

In this paper, the state of metastable equilibrium and the state of unstable equilibrium of water at a certain temperature are explored using an exact difference lattice Boltzmann model and the conditions of bubble (droplet) formation are investigated in the isothermal phase transition processes. From these simulation results, it is found that the model predictions are in good agreement with analytical results. Based on these works, a new model, which is based on exact difference lattice Boltzmann model and extended with an energy transfer equation to model heat transfer, is proposed to describe liquid-vapor phase transition process. The effects of the wall-fluid interaction strength on the bubble nucleation process in a pit are investigated using this new heterogeneous phase transition model. Simulation results accurately reproduce the characteristics of three stages of the bubble nucleation process. The changes of the contact angle, curvature radius, and volume with the bubble nucleation process are explored, and the relationship curve between curvature and bubble volume from the simulations is in qualitative agreement with the previous results.