bluuebunny/crossref_metadata_2025 huggingface dataset:
Constitutive equation of casting magnesium alloy ML308 based on void-cell model
Authors: Chen Bin  , Peng Xiang-He  , Sun Shi-Tao  , Quan Guo-Zheng  , Luo Ji  ,   重庆大学资源及环境科学学院，重庆  400044
Published: December 2020

Casting magnesium alloys are heterogeneous materials containing numerous voids. These voids markedly affect the mechanical behaviour of the materials. In this paper, a void-growth equation is obtained based on the analysis of a spherical void-cell model, and a void-nucleation equation is presented which is related to the increment of intrinsic-time measure. The evolution equation of the voids is obtained by combining the growth equation with the nucleation equation. The obtained void-evolution equation is incorporated into a nonclassical elastoplastic constitutive equation through introducing a softening function, thus obtaining a constitutive equation that involves a void evolution. A corresponding finite element procedure is developed and applied to the description of the rule of the void evolution and the mechanical behaviour of casting magnesium alloy ML308. Computed results are shown to be in satisfactory agreement with experimental data.
Up-conversion luminescence of CdTe and CdTe/CdS quantum dots excited by femtosecond laser of low intensity
Authors: An Li-Min  , Yang Yan-Qiang  , Song Wei-Si  , Su Wen-Hui  , Zeng Qing-Hui  , Chao Ke-Fu  , Kong Xiang-Gui  ,   (1)哈尔滨工业大学物理系，凝聚态科学与技术研究中心，哈尔滨  150001; (2)哈尔滨工业大学物理系，凝聚态科学与技术研究中心，哈尔滨  150001；黑龙江大学物理科学与技术学院，哈尔滨  150080; (3)中国科学院长春光学精密机械与物理研究所激发态物理重点实验室，长春  130033
Published: December 2020

We studied the steady-state and time-resolved luminescence properties of CdTe and CdTe/CdS core/shell quantum dots by one-and two-photon excitation with a femtosecond laser of low intensity. The 800 nm excitation causes a blue shift of the emission peak compared with 400 nm laser excitation. Near-quadratic laser power dependence of the up-conversion intensity and biexponential decay kinetics are observed. It is found that upconversion luminescence is composed of a photoinduced trapping and a band edge excitonic state. The blue shift of the emission peak is caused by the relative change in luminescence intensity between excitonic and trapping states. Two-step two-photon absorption involving the surface as intermediate states has been proposed for the mechanism of up-conversion luminescence of CdTe/CdS quantum dots.
Effect of Pt spacers on the interface of Co/FeMn
Authors: Fu Yan-Qiang  , Liu Yang  , Jin Chuan  , Yu Guang-Hua  ,   北京科技大学材料物理与化学系,北京  100083
Published: December 2020

Co/FeMn/Co multilayers were prepared by magnetron sputtering. The change of magnetic moments by insertion of Pt spacer at the Co （bottom）/FeMn interface and FeMn/Co （top） interface has been investigated. According to the hysteresis loops measured by alternating gradient magnetometer （AGM）, the saturation magnetization （Ｍs） of multilayers is changed by the Pt spacer at the Co （bottom）/FeMn interface, and there is an asymptotic approach of Ｍs to the theoretical value of Ｍs of the cobalt bulk of 1440 kA/m as the thickness of Co layer （tCo） is increased. This behavior is due to the production of net magnetic moments at the Co （bottom）/FeMn interface, which are decreased by Pt spacer at the Co （bottom）/FeMn interface. However, a significant difference between the Co （bottom）/FeMn interface and the FeMn/Co （top） interface is observed, as little influence of the Pt spacer on magnetic moments is shown when inserted at the FeMn/Co （top） interface.
Magnetism of aluminum atomic chains
Authors: Lin Qiu-Bao  , Li Ai-Yu  , Wen Yu-Hua  , Zhu Zi-Zhong  ,   (1)集美大学理学院,厦门  361021；厦门大学物理系,厦门  361005; (2)厦门大学物理系,厦门  361005; (3)厦门理工学院数理系,厦门  361024
Published: December 2020

By using the first-principles method based on the density functional theory, the magnetism of Al monoatomic chains have been studied. The present calculations show that both the linear and zigzag Al chains can exhibit ferromagnetism. However, the magnetism appears only when the Al chains are elongated. The underlying mechanism has been understood based on the atomic orbital interaction picture, taking into consideration the electronic density of states in combination with the Stoner criteria.
Modified effective medium modeling and seismic wave field in un-cemented marine sediments with hydrates
Authors: Li Hong-Xing  , Tao Chun-Hui  , Zhou Jian-Ping  , Deng Ju-Zhi  , Deng Xian-Ming  , Fang Gen-Xian  ,   (1)东华理工大学核工程技术学院,抚州  344000; (2)东华理工大学核工程技术学院,抚州  344000；国家海洋局第二海洋研究所,杭州  310012；国家海洋局海底科学重点实验室，杭州  310012; (3)国家海洋局第二海洋研究所,杭州  310012；国家海洋局海底科学重点实验室，杭州  310012
Published: December 2020

Elastic-wave velocity estimation in marine sediments with hydrates is an important part of hydrate seismic survey method and engineering. Suspending model and grain contact model are two main hydrate microscopic patterns for the non-cemented sediments with hydrates. Through numerical analysis, we discovered the velocity of compression wave and transverse wave and the Poisson's ratio forecasted by suspending model and grain contact model have bugs in physical understanding. Considering the hydrate microscopic model as the suspending model or grain contact model singly is unreasonable. We point out that the hydrate microscopic model is related with the hydrate saturation and established a modified effective medium modeling of non-cemented sediments with hydrates using the Lagrange interpolation method. This model considers the effect of hydrate saturation on the hydrate microscopic model, and the numerical analysis indicated that the new model is more reasonable. We made numerical simulation of seismic wave field based on the modified effective medium model and studied the characteristics and mechanism of BSR and blanking zone, and then expounded some phenomena observed practically based on the possiblly existing models.
Chaotic control of permanent magnet synchronous motor based on washout filter technique
Authors: Li Chun-Lai  ,   湖南理工学院物理与电子信息系，岳阳  414006
Published: December 2020

A chaos control method is presented in the paper for the permanent magnet synchronous motor （PMSM）, which uses the current of the PMSM as its feedback based on washout filter technique. Only the parameter of the filter is needed and no parameter of the original system will be affected by using the controller. Simulation result presents the simplicity, effectiveness and robustness of the method.
Density functional theory study of the interaction of H2 with rhodium clusters
Authors: Ge Gui-Xian  , Cao Hai-Bin  , Jing Qun  , Luo You-Hua  ,   (1)华东理工大学理学院，上海  200237; (2)石河子大学师范学院物理系，生态物理重点实验室，石河子  832003
Published: December 2020

The adsorption for H atoms on the Rhn cluster has been systematically investigated by density functional theory. The result indicates that the lowest energy structures of RhnH2 are generated with H atoms being adsorbed on the lowest energy structure of Rhn clusters, and the lowest energy structures of Rhn clusters are not changed by adsorbing H atoms. The total magnetic moment is affected by average bond distance. The chemisorption of H atoms on Rhn clusters belongs to dissociative adsorption. When H2 is absorbed on the Rhn clusters, the stability and chemical action of corresponding clusters are dramatically increased. The second order difference indicates 4 is magic number in RhnH2 and Rhn clusters. Among various possible adsorption sites, bridge site is energetically preferred for n≤5. The hollow site adsorption appears for n≥6.
Interactions of electromagnetic wave and Langmuir wave in an inhomogeneous plasma
Authors: Zhou Lei  , Tang Chang-Jian  ,   四川大学物理科学与技术学院,成都  610064
Published: December 2020

The linear conversion and interactions of Langmuir and electromagnetic waves in an inhomogeneous plasma has been demonstrated by numerical and theoretical methods adequately. The dispersion relation of electromagnetic wave in an inhomogeneous plasma has been deduced. The physical processes of conversion of incident electromagnetic or Langmuir wave in an inhomogeneous plasma and the relationship of the spread vector with the coordinates have been researched, and the mechanism of interactions between the electromagnetic and Langmuir waves have been discussed. The results are of significance for the generation of electromagnetic radiation from density gradient-driven plasma.
Pulse-front-distortion in large-aperture short-pulse laser systems
Authors: Zuo Yan-Lei  , Zeng Xiao-Ming  , Huang Xiao-Jun  , Zhao Lei  , Wang Xiao  , Zhou Kai-Nan  , Zhang Ying  , Huang Zheng  ,   中国工程物理研究院激光聚变研究中心，绵阳  621900
Published: December 2020

The principles of pulse-front distortions production and its possible sources in a large-aperture short-pulse laser system are described. By using Fourier optics, a theoretical model based on single-pass compression is set up for the study of the pulse-front distortion. For the first time the effects of the pulse-front distortion on the spatial and temporal properties of the output pulse from the compressor is investigated. With the model we analyze all kinds of distortion sources, including the AOPDF, the lens and the wedges by numerical simulation for a large-aperture short-pulse system. The result shows that the pulse width in the near field broadens remarkably and the pulse-front shape of the output pulse differs from that of the input pulse except in the central part in the cross section whose area is determined by the bandwidth of the system.
Analysis of the beam characteristics and the propagation model of spectral combining systems for Yb-doped fiber lasers
Authors: Pan Lei-Lei  , Zhang Bin  , Yin Su-Qin  , Zhang Yan  ,   四川大学电子信息学院，成都  610064
Published: December 2020

The propagation model for the spectral combining systems including Yb-doped fiber laser arrays，transform lens，grating and output coupler has been built up. By taking into considerotion the grating angle dispersion，the fabrication errors of groove angle and the diffraction efficiency of the grating，the formula for the phase change of the Gaussian beam unparallelly oblique incidence on the grating and the analytical expression for the intensity distribution of the combining beam have been derived by using the ray tracing method，the diffraction integral method，the principle of incoherent superposition of laser beams and the intensity second-order moments method. Consequently，the effects of the angle dispersion，the diffraction efficiency and the fabrication errors of groove angle of the grating on the beam characteristics of the spectral combining system have been analyzed for the case of Gaussian beam unparallelly oblique incidence on the grating. The results show that the beam quality of the combined beam remains almost the same as that of a single fiber laser. The effect of the angle dispersion of the grating on the beam quality of combined beam can be neglected. The beam quality of combined beam degrades with the increasing of the fabrication errors of groove angle of the grating. For the case of the large fabrication errors of groove angle of the grating，the effect of the diffraction efficiency of the grating on the beam characteristics of the combined beam should be considered.
Experimental research on phase detection and correction of two fiber amplifier based on active segmented mirrors
Authors: Yang Ruo-Fu  , Yang Ping  , Shen Feng  ,   (1)中国科学院光电技术研究所自适应光学重点实验室，成都  610209; (2)中国科学院光电技术研究所自适应光学重点实验室，成都  610209；中国科学院研究生院，北京  100049
Published: December 2020

The measurement of piston noise is a critical issue in coherent combining of fiber lasers. This paper presents a strip extracting algorithm, which get the amplitude of phase noise in fiber amplifier. By this algorithm, phase noise of fiber amplifier working in 10-3 W level is measured and real-time controlled by high-speed digital processing circuit and active segment mirrors. Experimental results indicate, that after closing the loop, fringe contrast improves from 0.09 to 0.25, intensity value of piston noise decreases from 1053.4 nm down to 116.7 nm; the calibration precision and bandwidth of the system achieve 1/10λ and ～50　Hz, respectively.
Octagonal photonic crystal fiber of birefringence
Authors: Yang Qian-Qian  , Hou Lan-Tian  ,   (1)燕山大学红外光纤与传感技术研究所，秦皇岛  066004; (2)燕山大学红外光纤与传感技术研究所，秦皇岛  066004；燕山大学亚稳材料制备技术与科学重点实验室，秦皇岛  066004
Published: December 2020

In this paper we propose a novel octagonal birefringent photonic crystal fiber，which shows birefringence when the size of several holes near the core is enlarged. The modal field，dispersion，confinement loss，birefringence of the fiber fundamental mode and the influence on birefringence of some parameters are simulated by multipole method. The dispersion，confinement loss，birefringence of the hexagonal photonic crystal fiber having the same parameters were also computed. By comparision，we conclude that the octagonal photonic crystal fiber have larger birefringence，smaller confinement loss and shorter wavelength of zero dispersion than the hexagonal photonic crystal fiber with the same parameters.
Sheath structure of a hot-cathode in plasma
Authors: Wang Dao-Yong  , Ma Jin-Xiu  , Li Yi-Ren  , Zhang Wen-Gui  ,   中国科学技术大学近代物理系，中国科学院基础等离子体物理重点实验室和磁约束等离子体理论中心，合肥  230026
Published: December 2020

The plasma sheath in the presence of virtual-cathode structure near a hot cathode was studied by combining the theory of thermionic emission and plasma fluid equations. Using Sagdeev potential method, the sheath solution and generalized Bohm criterion were discussed. It is shown that, different from usual Bohm sheath, the critical ion Mach number at the sheath-presheath edge is not an independent constant but depends on sheath potential drop as well as other parameters, owing to the fact that there exists large quantity of thermionic electrons near the hot cathode which has a significant influence on the whole sheath structure. The critical Mach number first increases and then decreases with the potential drop （from sheath-presheath edge to the virtual cathode）, and monotonically increases with the temperature of the hot cathode. In the plane geometry, there exists an appreciable quantity of residual thermionic electrons which traverse the virtual cathode and sheath and enter into bulk plasma.
Pore structure determination of mesoporous SiO2 thin films by slow positron annihilation spectroscopy
Authors: Wang Qiao-Zhan  , Yu Run-Sheng  , Qin Xiu-Bo  , Li Yu-Xiao  , Wang Bao-Yi  , Jia Quan-Jie  ,   (1)郑州大学物理工程学院，郑州  450001; (2)中国科学院高能物理研究所核分析技术重点实验室，北京  100049
Published: December 2020

Mesoporous silica thin films with different pore shapes were prepared by evaporation induced self-assembly method. The synchrotron radiation x-ray reflectivity and slow positron annihilation techniques were used to characterize the pore structures. The results indicated that with increase of the spin-coating speed, the pore structure transformed from 3-D cubic to 2-D hexagonal, the average porosity also decreased. The correlation of the film structures and positron annihilation parameters was songht for with FT-IR spectroscopy and isotropic inorganic pore contraction model.
Structure and optical properties of Ni-doped ZnO films
Authors: Lan Wei  , Tang Guo-Mei  , Cao Wen-Lei  , Liu Xue-Qin  , Wang Yin-Yue  ,   (1)兰州大学磁学与磁性材料教育部重点实验室，兰州  730000; (2)西北民族大学计算机科学与信息工程学院，兰州  730030
Published: December 2020

ZnO:Ni films with different doping concentrations （0—7at.%） have been deposited by radio frequency magnetron sputtering. The results of x-ray diffraction, including θ-2θ mode and rocking curve mode, indicate that the film doped with 5at.% Ni shows an excellent preferred growth along c-axis orientation. The （002） diffraction peak shifts to a larger angle, which implies that Ni atoms are incorporated into the ZnO lattice. For ZnO:Ni films with good transparency in the visible range, the optical band gap evaluated by the fitting method decreases linearly from 3.272 to 3.253 eV with increasing Ni concentration. Undoped ZnO film exhibits a green emission peak and Ni-doped ZnO films mainly emit a blue photoluminescence centred at 430 nm, we believe that they might be ascribed to crystal defects of oxygen vacancies and interstitial zinc, respectively.
Effect of the non-nearest-neighbor hopping on the electronic structure of armchair graphene nanoribbons
Authors: Jin Zi-Fei  , Tong Guo-Ping  , Jiang Yong-Jin  ,   浙江师范大学数理与信息工程学院，金华  321004
Published: December 2020

Based on the tight-binding model, the non-nearest-neighbor hopping terms of electrons are taken into account and the energy spectra of the armchair graphene nanoribbons （AGRNs） are given analytically. The changes of the energy band and the gap with the non-nearest-neighbor terms are discussed. The results show that the next-nearest-neighbor term can increase the gap and the third-nearest-neighbor term can narrow the gap. The competition relationship between the edge relaxation and the non-neighbor term is compared. When the width n is odd, the van Hove singularity from graphene sheets leads to the dispersion-less band. When the width of AGRNs goes to infinity, the spectrum of AGRNs tends to that of graphene sheets.
Characteristics of photoconductivity oscillation in semi-insulating GaAs photoconductive semiconductor switches
Authors: Shi Wei  , Xue Hong  , Ma Xiang-Rong  ,   (1)渭南师范学院物理与电子工程系,渭南  714000; (2)西安理工大学应用物理系,西安  710048; (3)西安理工大学应用物理系,西安  710048；渭南师范学院物理与电子工程系,渭南  714000
Published: December 2020

The 4 mm gap and 5 ns pulse width semi-insulating GaAs photoconductive switches were triggered by 532 nm laser pulse with gradual increase of bias voltage from 500 V in steps of 50 V until the emergence of nonlinear electrical pulse. The expermental results showed that the linear and nonlinear electrical pulse waveforms had smaller amplitude and varying degrees of oscillation reduction after going through a main pulse. Then the microscopic state and transport process of carriers （hot-electron） in the switch material were studied in detail using the quantum theory. It was found that in the DC bias electric field, when the relaxation time of the hot-electrons in the electron-electron and electron-phonon interaction process is longer than the carrier life, the photoconductivity oscillation can be caused by the change of mobility in the process of optoelectronic transport, which is the main cause for the output electrical pulse to show oscillations.
Influence of groove in metallic subwavelength slit on transmission properties
Authors: Zheng Xian-Hua  , Wang Ying-Qi  , Zhang Yan  ,   (1)首都师范大学物理系，北京市太赫兹波谱与成像重点实验室，太赫兹光电子学教育部重点实验室，北京  100048; (2)首都师范大学物理系，北京市太赫兹波谱与成像重点实验室，太赫兹光电子学教育部重点实验室，北京  100048；哈尔滨工业大学物理系，哈尔滨  150001
Published: December 2020

The influence of the structure and position of groove in a two-dimensional metallic subwavelength slit on transmission properties has been studied with the finite-difference time-domain method. The whole structure of slit with perpendicular groove could be regard as a LC oscillation circuit. The capacitance and inductance of this oscillation circuit will be altered when the structure of groove varies，so that the resonant transmission peaks shift. And the drive source of circuit changes when the position of groove moves along the slit, as a result the distribution of electromagnetic filed in the structure is changed also. So the resonant transmission peaks are split. In this paper， the change of resonant transmission peaks as each parameter of the groove changes is analyzed with the principle of LC resonance.
A physical-model of small-signal InP-based double heterojunction bipolar transistors and its parameter extraction technique
Authors: Ge Ji  , Jin Zhi  , Su Yong-Bo  , Cheng Wei  , Liu Xin-Yu  , Wu De-Xin  ,   中国科学院微电子研究所,北京  100029
Published: December 2020

The influence on the base-collector junction capacitance Cbc of the energy band structure of the InP heterojunction bipolar transistors is researched. A physical model of small-signal InP double heterojunction bipolar transistor （DHBT） is developed, which takes into account the base-emitter and collector-emitter metalisations by using two additional capacitances Cmb and Cmc. The resistance of the model is divided into the intrinsic resistance, the extrinsic resistance and the parasitic resistance. Meanwhile, a physically meaningful small-signal parameter extraction procedure for the model is presented, in which all the equivalent circuit elements are extracted without reference to numerical optimization. An experimental validation is carried out, and excellent results are obtained over a wide range of bias points, which demonstrates good modeling accuracy.
Structure and properties of the ferromagnetic shape-memory alloy Co50Ni20Ga30-xSix
Authors: Dai Xue-Fang  , Sun Chen-Guang  , Qu Jing-Ping  , Li Yang-Xian  , Zhu Wei  , Chen Jing-Lan  , Wu Guang-Heng  ,   (1)河北工业大学材料学院，天津  300130; (2)中国科学院物理研究所北京凝聚态物理国家实验室，北京  100080
Published: December 2020

The structure，martensitic transformation and magnetism have been studied in the CoNiGa alloys after certain Ga substrated by Si. From the experimental results，we found that the alloy can form pure body-centered cubic structure accompanied by good thermal martensitic transformation when the atom ratio of Si lies in the range 0—10%. It can be concluded from further analysis that it is not only the radius of the doped atom but also the radius ratio of the doped atom and the host atom that affect the stability of the austenite. At the same time，it can be found that the Curie temperature and the saturated magnetization decrease with increasing Si. But the anisotropy of the martensite increases with the increasing Si，which is of significance for obtaining large magnetically-induced-strain.
High efficiency phosphorescence light-emitting diodes with conjugated polymer host
Authors: Niu Qiao-Li  , Zhang Yong  , Fan Guang-Han  ,   华南师范大学光电子材料与技术研究所，广州  510631
Published: December 2020

Polymer hosted phosphorescent light-emitting diodes （PLEDs） were attractive because of their high efficiency light-emission and easy fabrication technology using solution process. For green phosphorescence PLEDs，non-conjugated polymer，such as poly （N-vinylcarbazole） （PVK），were often used as host；while conjugated polymer have been proved to quench phosphorescence emission because of their low-lying triplet energy level. In this article，high efficiency phosphorescent green-emission was obtained with conjugated polymer of poly （9，9-dioctylfluorene） （PFO） as host using the device structure of ITO/poly （ehtlenedioxythiophene）: poly （styrene sulfonic acid） （PEDOT: PSS） （50 nm）/PVK （40 nm）/emissive layer （EML） （80 nm）/Ba （4 nm）/Al （150 nm）. The EML were PFO doped with different concentration of fac-tris （2-phenylpyridine） iridium （Ⅲ） （Ir（ppy）3） in weight. The PLED with 2 wt% Ir（ppy）3 demonstrated the maximum luminous efficiency of 24.8 cd/A at current density of 4.65 mA/cm2 and power efficiency of 11 lm/w with the peak emission at 520 nm. The luminance reached 35054 cd/m2 at the current density of 265 mA/cm2. According to analyzsis，the hole transport layer PVK can play important role in obtaining highly efficient green light emissing，whose electrons blocking effect resulted in the interfacial emissing center, and then the interfacial PVK enhanced green emission through energy transfer due to its high triplet enery level.
Numerical simulation of arc properties and their effects on the weld shape
Authors: Lu Shan-Ping  , Dong Wen-Chao  , Li Dian-Zhong  , Li Yi-Yi  ,   中国科学院金属研究所，沈阳材料科学国家（联合）实验室，沈阳  110016
Published: December 2020

A mathematical model of mutually coupled welding arc and weld pool is established for moving tungsten inert gas welding process on SUS304 stainless steels to investigate the argon and the helium arc properties and their effects on the weld shapes. The comparisons of the temperature contour, the current density and the heat flux on the anode surface between the argon and the helium arcs show that the helium arc is more constricted than the argon arc and transfers more heat fluxes to the anode. The effects of buoyancy, electromagnetic force, Marangoni force and drag individually on the weld pool are simulated, and simulation results show that the Marangoni force on the pool surface is one of the main forces affecting the weld shape, independent of shielding gases. Under argon arc, an other dominant force is the plasma drag force. However, the effect of electromagnetic force is stronger than that of the plasma drag force in helium arc. The inward convection induced by the electromagnetic force increases the weld depth, thereby leading the weld depth and the D/W ratio in helium arc to be larger than the ones in argon arc under the same oxygen content. The weld D/W ratio increases first and then maintains a constant with the increase of oxygen content for both argon arc and helium arc. The weld D/W ratio obtained by simulation is in good agreement with experimental results.
Analysis on fractional Oldroyd-B viscoelastic Poiseuille flow by numerical inversion of Laplace transforms
Authors: Wang Yu  , Ouyang Jie  , Yang Bin-Xin  ,   Department of Applied Mathematics, Northwestern Polytechnical University, Xi’an 710129, China
Published: December 2020

In this paper the unsteady Poiseuille flow of fractional Oldroyd-B viscoelastics fluid between two parallel plates is studied, which sheds light on the investigation on fractional differential equations. Stehfest algorithm for numerical inversion of Laplace transform is used for obtaining the numerical solutions, and its validity is verified by comparing the results with approximate analytic solutions. Then the laminar Poiseuille flow of fractional Oldroyd-B viscoelastic fluid is investigated by the Stehfest algorithm. Phenomena of velocity and stress overshootings are found, which are proved to be dependent on the order of fractional derivative. Simultaneously, compared with the integer constitutive equations, the fractional constitutive equations have wider scope of application. This conclusion was drawn based on the obvious fact that the integer constitutive equations are only special cases of the fractional constitutive equations.
Simulation of vapor-liquid coexistence using dissipative particle dynamics
Authors: Wang Xiao-Liang  , Chen Shuo  ,   School of Aerospace Engineering and Applied Mechanics, Tongji University, Shanghai 200092,China
Published: December 2020

Due to a purely repulsive conservative interaction adopted in the traditional dissipative particle dynamics, the vapor-liquid coexistence phenomena or fluid flows with free surfaces could not be simulated. In the present study a recently proposed combination of short-range repulsive and long-range attractive interaction for DPD was investigated to explore its ability of simulating vapor-liquid coexistence or fluid flows with free surfaces. With this modified interaction, steady vapor-liquid interface could be obtained in DPD simulation, and the stress distribution across the vapor-liquid interface region was also discussed, which were found in accordance with those obtained by multibody DPD. Furthermore, surface tension of vapor-liquid interface was studied, and it was verified that Laplace’s law is satisfied in our simulation. Surface tensions obtained by theoretical method and Laplace’s law, respectively, are in agreement with each other.
Dipole squeezing of atomic systems in dissipative environment
Authors: Fang Mao-Fa  , Pan Chang-Ning  , Zhao Xue-Hui  , Yang Di-Wu  ,   (1)College of Physics and Information Science, Hunan Normal University, Changsha 410081, China; (2)School of Science, Hunan University of Technology, Zhuzhou 412008, China
Published: December 2020

The atomic squeezing effect in the dissipative environment is investigated by means of the quantum theory of damping-density operator approach and numerical calculations. The effects on the atomic dipole squeezing effect produced by the atomic initial state and mean photon number of the thermal reservoir are discussed. The results show that the atomic dipole squeezing declines asymptotically to zero, and doesn’t disappear in finite time if the population rate in the excited state is higher than the ground state in the atomic initial state in the vacuum reservoir. However, the squeezing effect always disappears in the thermal reservoir, irrespective of the atomic initial state. With increase of mean photon of the thermal reservoir, the squeezing effect disappears faster.
Calculation of meniscus force during separation of microsurfaces
Authors: Liu Si-Si  , Zhang Chao-Hui  , Liu Jun-Ming  ,   School of Mechanical, Electronic and Control Engineering, Beijing Jiaotong University, Beijing 100044, China
Published: December 2020

The adhesive force between microsurfaces is very important to microelectric mechanical system (MEMS), being always a key factor that detemines the energy dissipation and even the life span. In MEMS, the meniscus force mainly depends on the meniscus shape formed between the contact surfaces. This paper analyzes the meniscus shape changes during the seperation of two microsurfaces. Different meniscus shapes were obtained as a result of different hydrophilic/hydrophobic properties, initial liquid heights and separate distances and so on. The fracture height, the meniscus force value and their change rules in different initial conditions are obtained by numerical simulation, which provides a basis of the MEMS performance analysis and life span calculation.
Spectroscopic studies of molecular ions and their dissociation dynamics by the threshold photoelectron-photoion coincidence
Authors: Tang Xiao-Feng  , Niu Ming-Li  , Zhou Xiao-Guo  , Liu Shi-Lin  ,   Hefei National Laboratory for Physical Sciences at Microscale, Department of Chemical Physics, University of Science and Technology of China, Hefei 230026, China
Published: December 2020

In a recently built threshold photoelectron-photoion coincidence spectrometer, the photoelectrons and photoions were velocity-focused simultaneously to effectively improve the collection efficiency and the energy resolution. With this spectrometer we measured the threshold photoelectron spectra (TPES) and the mass-selected threshold photoelectron-photoion coincidence mass spectra (TPEPICO-MS) of NO molecules, as well as Xe/Ar/Ne rare gas mixtures. The ionization potential of NO was accurately determined, and the vibrationally resolved TPES spectra of the X1Σ+, c3Π and B1Π states of NO+ were obtained. Subsequently, the dissociation dynamics of the c3Π state of NO+ were studied by measuring the TPEPICO-MS and fitting the time-of-flight profile of the N+ fragment. The overall kinetic energy released from dissociation was determined to be 0.717 eV.
Laser one-dimensional range profile
Authors: Li Yan-Hui  , Wu Zhen-Sen  , Gong Yan-Jun  , Zhang Geng  , Wang Ming-Jun  ,   School of Science, Xidian University, Xi'an 710071, China
Published: December 2020

Pulse laser one-dimensional range profile theory and simulation are investigated. Laser one-dimensional range profile simulation is studied based on pulse wave scattering theory and the radar equation, and the calculated formula of laser one-dimensional range profile is obtained. As examples, the range profile simulations are calculated for the sloped-plane, sphere, and cone. It is also analyzed that the influences of target shape, radial length and pulsewidth on the simulation results. This paper offers theory bases and simulation method for abstraction and identification target feature on the laser.
Two-photon absorption coefficient spectra of indirect transitions in silicon
Authors: Li Zhi-Feng  , Ma Fa-Jun  , Chen Xiao-Shuang  , Lu Wei  , Cui Hao-Yang  ,   (1)National Laboratory for Infrared Physics, Shanghai Institute of Technical Physics, Chinese Academy of Sciences, Shanghai 200083, China; (2)School of Computer Science and Information Engineering, Shanghai University of Electric Power, Shanghai 200090, China, National Laboratory for Infrared Physics, Shanghai Institute of Technical Physics, Chinese Academy of Sciences, Shanghai 200083, China
Published: December 2020

The two-photon absorption coefficient spectra of indirect transitions in silicon have been measured using a picosecond Nd:YAG pulsed laser pumped optical parametric generator, whose wavelength being tunable. By employing the pulsed laser with the photon energy less than the indirect energy gap of silicon, the photovoltaic response between two electrons of the silicon photovoltaic diode has been detected significantly. The peak intensity of the pulsed photovoltaic response shows a quadratic dependence on the incident intensity. This suggests a typical two photon absorption process. A relationship between the pulsed photovoltaic response and the incident intensity has been established with an equivalent RC circuit model to derive the two-photon absorption coefficient, and the spectra can also be obtained by turning the incident wavelengths. The results show that when the incident photon energy change from 0.689 eV to 0.912 eV, the two-photon absorption coefficient increase form 0.42 cm/GW to 1.17 cm/GW. The mechanism for the two-photon absorption coefficient increasing with the incident photon energy can be attributed to the electrons excited from valance band finding an increasing availability of conduction-band states as the photon energy increase from Eig/2 to near Eig. This photon frequency dependence of the two-photon absorption coefficient has been fairly interpreted by the Dinu model.
Structural damage imaging based on time-reversal theory for focusing of Lamb waves
Authors: Zhang Hai-Yan  , Sun Xiu-Li  , Cao Ya-Ping  , Chen Xian-Hua  , Yu Jian-Bo  ,   School of Communication and Information Engineering, Key Laboratory of Specialty Fiber Optics and Optical Access Networks, Shanghai University, Shanghai 200072, China
Published: December 2020

This study presents a theoretical and experimental investigation of the application of the time-reversed concept to dispersive and multimode Lamb waves for health monitoring of plate-like structures. When a Lamb wave signal is excited in a plate-like structure with damage,the damage will serve as a passive wave source. With the transfer function,the focusing in the time-reversal field composed of distributed transducer network is analyzed by deducing the amplitude expression of the time reversal Lamb wave signals. The result demonstrates that time-reversal signal reaches the maximum amplitude when the observation point is located at the damage location. To validate the focusing effect of the time-reversal method,an efficient imaging method suitable for distributed actuator/sensor networks is adopted for locating and approximate sizing of structural damages. Experimental results combined with finite element simulation illustrate that the inspection energy can be focalized on the damage. It indicates that the time-reversal method is an effective way for identifying and locating damage for Lamb wave inspection.
Electrostatic oscillation and coupling resonance in double trap of unbalanced magnetron sputtering
Authors: Mu Zong-Xin  , Mu Xiao-Dong  , Jia Li  , Wang Chun  , Dong Chuang  ,   Key Laboratory of Materials Modification by Laser, Ion and Electron Beams of Ministry of Education, School of Physics and Optoelectronic Technology, Dalian University of Technology, Dalian 116024, China
Published: December 2020

The coupling resonance is induced by the plasma electrostatic oscillation in the magnetic trap consisting of the cross-field at the surface of the unbalanced magnetron sputtering target and the potential well composed of the magnetron sputtering target and the opposite bias substrate in parallel. Langmuir probe was used to study the plasma properties and power spectra density (PSD) of the floating potential signals. Under typical discharge conditions, the eigenfrequencies in both traps were respectively in the range of 30—50 kHz or 10—20 kHz, and the electron temperatures in both traps calculated with the acoustic standing wave mode conformed with the experimental results.
Runaway electrons behaviors during ion cycolotron range of frequency and lower hybrid wave plasmas in the HT-7 Tokamak
Authors: Lu Hong-Wei  , Hu Li-Qun  , Zhou Rui-Jie  , Xu Ping  , Zhong Guo-Qiang  , Lin Shi-Yao  , Wang Shao-Feng  ,   Institute of Plasma Physics, Chinese Academy of Sciences, Hefei 230031, China
Published: December 2020

HT-7 Tokamak is equipped with a lower hybrid wave (LHW) system and an ion cyclotron range of frequency (ICRF) system. ICRF can accelerate ions effectively, while LHW can accelerate electrons effectively. The generation of runaway electrons during the LHW and ICRF plasmas, as well as the time evolution of electron temperature during the ICRF and LHW plasmas was investigated in this paper. The runaway critical energy for runaway electrons was also calculated according to the experimental data. It was observed that the combination of ICRF and LHW can produce a higher heating efficiency and a better coupling between ICRF and plasmas if the power of LHW exceeds a critical value. Therefore, the generation of runaway electrons and fusion neutrons are affected by ICRF.
On the effect of magnetic field gradient on the discharge characteristics of Hall thrusters
Authors: E Peng  , Duan Ping  , Jiang Bin-Hao  , Liu Hui  , Wei Li-Qiu  , Xu Dian-Guo  ,   (1)College of Physics Science and Technology, Dalian University, Dalian 116622, China; (2)Department of Electrical Engineering, Harbin Institute of Tchnology, Harbin 150001, China
Published: December 2020

An experiment was performed to investigate how the magnetic field gradient in strong field zone affects the discharge processes of Hall thrusters, such as the ionization and acceleration of propellants, for further research on optimal design theory of magnetic field in discharge channels of Hall thrusters. The results show that magnetic field strength has little effect on the ionization of propellants within the designed range of magnetic field gradient, but has significant influence on the acceleration of ions.With the increase of magnetic field gradient, the ion-beam energy distribution tends to be concentrated, and the thrust efficiency tends to rise. Finally, further increase of magnetic field gradient may lead to a series of physical problems,among whith such as the finite Larmor radius effect, the changes in the law of electronic conduction mechanism, and the magnetic field gradient drift are analyzed.
Influence of doping on the crystallization ability of mono-component materials
Authors: Peng Kun  , Ming Chen  , Ye Xiang-Xi  , Zhang Wen-Xian  , Zhuang Jun  , Ning Xi-Jing  ,   (1)Department of Optics Science and Engineering, Fudan University, Shanghai 200433, China; (2)Key Laboratory of Applied Ion Beam Physics Laboratory of Ministry of Education, Institute of Modern Physics, Fudan University, Shanghai 200433, China
Published: December 2020

Recently, we developed a condensing potential model to predict the ability for materials to form single crystals, and it showed that the ability of mono-component materials (Ni, Al, Cu, Ar, Mg) increases monotonically with the increasing condensing potentials. The present work applied the condensing potential model to binary-component materials. Via molecular dynamics simulations, we investigated the influence of 6 wt% Al doping on the crystallization ability of Ni crystal and found that the doping heavily decreased the crystallization ability. Then a condensing potential model for binary-component materials was developed and was shown as a promising tool to predict the crystallization ability of binary-component materials.
Quasicontinuum simulation of crack propagation in nanocrystalline Ni
Authors: Shao Yu-Fei  , Wang Shao-Qing  ,   Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016, China
Published: December 2020

The propagation process of crack in the nanocrystalline Ni is simulated via the quasicontinuum method. The results show that the stress near the crack tip could prompt the disassociation of grain boundaries, and the formation of stacking faults and deformation twins. Farther from the crack tip, fewer deformation twins can be found. There are more stacking faults than deformation twins in the grains, which approximately have the same distance to the crack tip. The effect on deformation twins from the variation of local stress and generalized planar fault energies is manifested by these results. The distribution of hydrostatic stress on atomic-level around the crack tip is also calculated. It is shown that nanovoids can be easily created in grain boundaries in front of the crack tip. There exists an intense tensile stress state in the grain boundary regions around these nanovoids. As a result of the stress accumulation, the crack propagates along the grain boundaries. Our simulated results qualitatively uncover the propagation process of crack in nanocrystalline Ni, which agrees well with the relevant experimental results.
Phonon band structure and electron-phonon interactions in Ga and Sb nanowires: a first-principles study
Authors: Sun Wei-Feng  , Li Mei-Cheng  , Zhao Lian-Cheng  ,   Department of Information Material Science and Technology, Harbin Institute of Technology, Harbin 150001, China
Published: December 2020

We present first-principles calculations of the electronic and phonon band structure considering electron-phonon coupling in thin Ga and Sb nanowires. A full Brillouin zone analysis of the phonons is performed for the investigation of nanowire structural stability. The examined nanowires show instability while the wave vectors are away from the zone center. Compared with the usual Peierls distortion picture, the unstable transverse phonon modes induce a transition without electronic band-gap opening. Electron-phonon interaction yields orders-of-magnitude changes depending on the nanowire structure.
Effect of molecular internuclear distance on non-sequential double ionization
Authors: Wei Ya-Na  , Yang Shi-Ping  ,   Department of Physics, Hebei Normal University, Shijiazhuang 050016, China
Published: December 2020

Using the semiclassical rescattering model, we have studied the effect of molecular internuclear distance on non-sequential double ionization. In the process of our analysis, the non-sequential double ionization rate, two-electron ionization energy, two-electron momentum correlation and the combined potential of Coulomb field and laser field are calculated with the molecular internuclear distance changing. The results show that non-sequential double ionization rate and the double ionization events with the sum of the two electron momentums equal to zero increase with the molecular internuclear distance increasing when the molecular internuclear distance is within 1.0—6.0 a.u. When the molecular internuclear distance continues to increase (greater than 6.0 a.u.), non-sequential double ionization rate and the double ionization events with sum of two electron momentums equal to zero decrease.
Cryogenic thermoelectric properties of BiTe-based alloys and cryo-energy power generation
Authors: Jiang Ming-Bo  , Wu Zhi-Xiong  , Zhou Min  , Huang Rong-Jin  , Li Lai-Feng  ,   (1)The Key Laboratory of Cryogenics, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100190, China; (2)The Key Laboratory of Cryogenics, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100190, China, Graduate Univesity of Chinese Academy of Sciences, Beijing 100190, China
Published: December 2020

The BiTe-based alloys were fabricated by mechanical alloying and cold-pressing sintering. Seebeck coefficient and electrical conductivity were measured at the temperature range of 80—300 K. Results showed that the thermoelectric properities of the materials were excellent during the experiments. With the thermoelectric conversion device made of BiTe-based alloys, a new cryo-energy utilization equipment were established. By applying liquid nitrogen in the experiments, the cryo-energy was released during evaporation of liquid nitrogen, and then, a study of electric properties of thermoelectric conversion devices was further deployed. The relationship of output voltage and output power versue current intensity was obtained from the experiments. The maximum output power in the experiments was up to 1.33 W,which verified the feasibility of cryo-energy power generation.
Energy levels and magnetic moments of the quantum solitary wave in a one-dimensional ferromagnetic chain
Authors: Li De-Jun  , Mi Xian-Wu  , Deng Ke  ,   College of Physics Science and Information Engineering, Jishou University, Jishou 416000, China
Published: December 2020

By using the Hartree approximation and the simplified method of quasidiscreteness multiple scales, we have studied quantum solitary wave solutions for a one-dimensional ferromagnetic chain with exchange interaction and classical magnetic moment interaction. In this chain there are both traveling and stationary quantum solilary waves. With the help of the obtained quantum solitary wave solution, the energy levels and magnetic moments of the quantum solitary wave have been investigated further. It is shown that the energy and magnetic moments of the quantum solitary wave are quantized. These novel results provide a possible way for understanding macroscopic quantum effects such as quantum steps of the hysteresis loop in magnetic materials.
Design and thermodynamical analysis of a new refrigerator model driven by photovoltaic and thermoelectric power generation
Authors: Yang Zheng-Long  , Liu Yong-Sheng  , Gu Min-An  , Yang Jing-Jing  , Shi Qi-Guang  , Gao Tian  , Yang Jin-Huan  ,   (1)Institute of Functional Polymer Materials, Tongji University, Shanghai 200092, China; (2)Institute of Solar Energy, Shanghai University of Electric Power, Shanghai 200090, China
Published: December 2020

According to solar cell’s temperature properties and thermoelectric power properties, a refrigerator model is newly designed, which is driven by solar photovoltaic and thermoelectric power generation. It includes solar cells, thermoelectric power modules, power control system, etc. Based on the load demand for electricity, a photovoltaic power generation system is designed. The operating efficiency and exergy efficiency of the model are analyzed by thermodynamic theory. We find that the COP (coefficient of performance) achieves 2.73 (COP is about 2 for general refrigerators) and exergy efficiency achieves 42.5%. By using the model, the emissions of carbon dioxide 1394.2 kg, sulfur dioxide 27.2 kg and nitrogen oxides 21.0 kg are reduced, which can provide an interesting direction to the applications of renewable energy.
Influence of excitation frequency on the growth properties of nanocrystalline silicon films with high hydrogen dilution
Authors: Song Jie  , Guo Yan-Qing  , Wang Xiang  , Ding Hong-Lin  , Huang Rui  ,   Department of Physics and Electrical Engineering, Hanshan Normal University, Guangdong 521041, China
Published: December 2020

Nanocrystalline silicon films were prepared from SiH4 highly diluted with hydrogen by plasma enhanced chemical vapor deposition. The influence of excitation frequency on their growth properties was investigated. The cross-section transmisson electron microscopy images show that all the films grow with certain fastigiated structure in the crystalline region. However, the films deposited at 13.56 MHz undergo a transition from amorphous incubation layer to crystalline structure. In contrast, for the films deposited at a high excitation frequency (40.68 MHz), nanocrystalline silicon grains can directly grow on the amorphous substrates. Furthermore, the results of Raman spectra and Fourier transform infrared spectroscopy manifest that the nanocrystalline silicon films deposited at high excitation frequency (40.68 MHz) possess high crystalline fraction, low hydrogen content and small microstructure factor.