bluuebunny/crossref_metadata_2025 huggingface dataset:
Simulation of two-dimensional nonlinear problem with solitary wave based on split-step finite pointset method
Authors: Ren Jin-Lian , Ren Heng-Fei , Lu Wei-Gang , Jiang Tao ,   School of Mathematical Sciences, School of Hydraulic, Energy and Power Engineering, Yangzhou University, Yangzhou 225002, China
Published: December 2020

In this paper, a split-step finite pointset method (SS-FPM) is proposed and applied to the simulation of the nonlinear Schrödinger/Gross-Pitaevskii equation (NLSE/GPE) with solitary wave solution. The motivation and main idea of SS-FPMisas follows. 1) The nonlinear Schrödinger equation is first divided into the linear derivative term and the nonlinear term based on the time-splitting method. 2) The finite pointset method (FPM) based on Taylor expansion and weighted least square method is adopted, and the linear derivative term is numerically discretized with the help of Wendland weight function. Then the two-dimensional (2D) nonlinear Schrödinger equation with Dirichlet and periodic boundary conditions is simulated, and the numerical solution is compared with the analytical one. The numerical results show that the presented SS-FPM has second-order accuracy even if in the case of non-uniform particle distribution, and is easily implemented compared with the FDM, and its computational error is smaller than those in the existed corrected SPH methods. Finally, the 2D NLS equation with periodic boundary and the two-component GP equation with Dirichlet boundary and outer rotation BEC, neither of which has an analytical solution, are numerically predicted by the proposed SS-FPM. Compared with other numerical results, our numerical results show that the SS-FPM can accurately display the nonlinear solitary wave singularity phenomenon and quantized vortex process.
Surface plasmon mediated chemical reaction
Authors: Zhang Bao-Bao , Zhang Cheng-Yun , Zhang Zheng-Long , Zheng Hai-Rong ,   School of Physics and Information Technology, Shaanxi Normal University, Xi'an 710119, China
Published: December 2020

Surface plasmons are collective oscillations of free electrons at the interface between metal and dielectric. Surface plasmons can break through the diffraction limit of light, because the electromagnetic field is confined in a very small space near the surface of the nanostructure, which provides a possibility for nanometer-scale light manipulation. By using surface plasmon resonance, the local surface electromagnetic field can be strongly enhanced, which can be used to enhance the molecular fluorescence and Raman signals. In addition, the plasmon relaxation induces thermal electrons which can drive the catalytic reaction of surface molecules to achieve a selective catalytic reaction at normal temperature, which is so-called plasmon mediated chemical reaction (or plasmonic catalysis). As a new type of catalytic system, plasmonic catalysis can mediate chemical reactions that are difficult to occur under various conventional conditions. Due to the complexity and diversity of plasmon catalyzed reactions, it is still a huge challenge to fully characterize the reaction kinetics and understand its reaction mechanism. Characterizing the intermediate and final products in the catalytic reaction accurately and obtaining more detailed information in the reaction process are essential for exploring the theoretical mechanism of plasmon catalysis. In this paper, we review the characterization techniques used in plasmon catalysis in detail in the progress of plasmon catalysis. First, the basic concepts of plasmon catalysis and several common catalytic mechanisms are introduced. Second, the Raman spectroscopy, including the application of surface and tip-enhanced Raman spectroscopy in plasmon catalytic in situ monitoring are reviewed. Then, the other techniques such as gas chromatography, gas chromatography-mass spectrometry, high performance liquid chromatography, scanning transmission electron microscopy, scanning tunneling microscopy, scanning electrochemical microscopy and UV-visible absorption spectroscopy for monitoring plasmon catalyzed reaction are introduced in detail. Finally, the characteristics and advantages of these characterization techniques in the study of kinetic catalytic process and catalytic mechanism of plasmon, and the future development and challenge are mentioned and analyzed.
Research progress of solution processed all-inorganic perovskite solar cell
Authors: Wang Ji-Ming , Chen Ke , Xie Wei-Guang , Shi Ting-Ting , Liu Peng-Yi , Zheng Yi-Fan , Zhu Rui ,   Siyuan Laboratory, Guangzhou Key Laboratory of Vacuum Coating Technologies and New Energy Materials, Guangdong Provincial Engineering Technology Research Center of Vacuum Coating Technologies and New Energy Materials, Department of Physics, Jinan University, Guangzhou 510632, China,   State Key Laboratory For Artificial Microstructure and Mesoscopic Physics, Peking University, Beijing 100871, China,   Collaboration Innovation Center of Extreme Optics, Shanxi University, Taiyuan 030006, China
Published: December 2020

Photovoltaic technology, which can converse solar illumination into electricity, is crucial to the sustainable development of human civilization. Among them, the organic-inorganic hybrid perovskite solar cell (OIPSC) has become a research front due to its excellent photoelectric characteristics, low production cost and high power conversion efficiency (PCE). Although the PCE of OIPSC has exceeded 24%, the organic components in the perovskite system are sensitive to the decomposion caused by either being exposed to light or heated in high temperature environment. The stability defects have greatly limited the commercialization of perovskite solar cells. Therefore, it is urgent to improve the stability of perovskite solar cells, especially to solve the material decomposition problem. All-inorganic perovskite photovoltaic material, composed of all-inorganic elements, exhibits excellent heat and moisture resistance. Therefore, the development of all-inorganic perovskite solar cells is of great significance for solving the current stability problems in perovskite photovoltaics. In this work, we review the recent research progress of all-inorganic perovskite solar cells, discuss the solution approaches to processing all-inorganic perovskite films, and explore the enhancement of device stability. Our work provides a guideline for further promoting the device stability and PCE.
Dipole orientation polarization property of single-molecule manipulated by external electric field
Authors: Wu Rui-Xiang , Zhang Guo-Feng , Qiao Zhi-Xing , Chen Rui-Yun ,   College of Physics and Information Engineering, Shanxi Normal University, Linfen 041004, China,   Key Laboratory of Spectral Measurement and Analysis of Shanxi Province, Shanxi Normal University, Linfen 041004, China,   State Key Laboratory of Quantum Optics and Quantum Optics Devices, Institute of Laser Spectroscopy, Shanxi University, Taiyuan 030006, China,   Department of Radiology, First Clinical Medical College, Shanxi Medical University, Taiyuan 030001, China
Published: December 2020

The dipole orientation of single-molecule plays an important role in improving the fluorescence collection efficiency and promises to have applications in super-resolution imaging, protein folding, and Förster resonance energy transfer between fluorophores. However, these applications are realized usually by precisely manipulating the orientation of the dipole moment of single molecules. Here, the dipole orientation of 1,1′-dioctadecyl-3,3,3′,3′,-tetramethylindodicarbocyanine (DiD) single molecules with the permanent dipole moment of 14.9 D is manipulated by using an external electric field of 3500 V/mm. Single DiD molecules are prepared by using mixed solvent of chloroform and dimethyl sulfoxide. The dipole orientation of single molecules is manipulated by an external electric field during the evaporation of solvent. The fluorescence of single molecules is measured by splitting the fluorescence collected by an objective into the S-polarized and P-polarized beams, and the fluorescence polarization of single molecules can be calculated by measuring the intensities of two orthogonal channels (IS and IP). The distribution of dipole orientation angle (α) for single DiD molecules in poly-(methyl methacrylate) (PMMA) film is analyzed statistically, and its changes are compared under different electric fields. It is found that the dipole orientation angle α of single DiD molecules in the PMMA film without applying electric field obeys a single-peak Gaussian distribution with the most probable value of 41°, which results from the fluorescence dichroism signal of the high numerical aperture objective. Applying a perpendicular electric field to the surface of single-molecule sample, the distribution of dipole orientation angle α of single DiD molecules can be still fitted by a single-peak Gaussian function with the most probable value of 44.2°. The dipole orientation of single DiD molecules under the perpendicular electric field changes little. However, by applying a parallel electric field to the surface of single-molecule sample, the dipole orientation angle α of single DiD molecules changes prominently. It obeys a two-peak Gaussian distribution with the most probable values of ～ 32° and 55.5°, indicating that the orientation polarization of the dipole moment occurs to the single DiD molecules in PMMA film. The dipole orientation of single polar molecules tends to the parallel electric field in this case.
Effects of ion irradiation and oxidation on point defects in IG-110 nuclear grade graphite
Authors: Li Ming-Yang , Zhang Lei-Min , Lv Shasha , Li Zheng-Cao ,   Department of Engineering Physics, Tsinghua University, Beijing 100084, China,   China North Nuclear Fuel Co., Ltd., Baotou 014035, China,   College of Nuclear Science and Technology, Beijing Normal University, Beijing 100875, China,   Key Laboratory of Advanced Materials (MOE), School of Materials Science and Engineering, Tsinghua University, Beijing 100084, China
Published: December 2020

Nuclear grade graphite is a kind of key material in the high temperature gas-cooled reactor pebble-bed module (HTR-PM), where nuclear grade graphite acts as the fuel element matrix material, structural material and neutron reflector. In the reactor, the service environment of nuclear grade graphite suffers high temperature and strong neutron radiation. Both neutron radiation and the oxidation by the oxidizing impurities in HTGR coolant can cause the structure to damage and the properties to deteriorate. Therefore, it is of great significance to study the evolution of defects in nuclear grade graphite for improving the reactor safety. The effects of ion irradiation and oxidation on the point defects in IG-110 graphite are studied in this work. The 190 keV He+ implantation treatments at room temperature with fluences of 1 × 1015, 5 × 1015, 1 × 1016 and 1 × 1017 cm–2 are performed to induce 0.029, 0.14, 0.29 and 2.9 displacements per atom respectively. Oxidation treatments are performed at 850 ℃ for 10, 15, 20 and 25 min. Different sequences of He+ ion irradiation and oxidation are performed, which include irradiation only (Irr.), oxidation only (Ox.), irradiation followed by oxidation (Irr.-Ox.), and oxidation followed by irradiation (Ox.-Irr.). Raman spectrum shows that with the increase of ion irradiation dose, the intensity ratio of D peak to G peak (ID/IG) first increases and then decreases, implying that the point defects in graphite are induced by ion irradiation and the point defects evolve as dose increases; the degree of graphitization increases after oxidation, implying that the point defects are recovered by the annealing effect at high temperature, and the point defects decrease after oxidation. This makes Ox.-Irr. samples have a lower point defect content than Irr. samples, and leads Irr.-Ox. samples to possess a higher point defect content than Ox. samples. The positron annihilation Doppler broadening tests reveal that there are only point defects after ion irradiation and oxidation have partially recovered point defects. The ion irradiation and oxidation have opposite effects on the evolution of point defect in graphite. The ion irradiation increases the average S-parameter and reduces the average W-parameter, while oxidation reduces the average S-parameter and increases the average W-parameter. The annealing effect at 850 ℃ cannot completely recover the point defects in Irr.-Ox. samples.
Numerical analysis of influence of thermochemical model on hypersonic magnetohydrodynamic control
Authors: Ding Ming-Song , Jiang Tao , Dong Wei-Zhong , Gao Tie-Suo , Liu Qing-Zong , Fu Yang-Ao-Xiao ,   Computational Aerodynamics Institute, China Aerodynamics Research and Development Center, Mianyang 621000, China
Published: December 2020

 In hypersonic flow, extremely high temperature due to shock aerodynamic heating leads plasma flow to form. By adding energy and momentum to the plas-ma flow field through the magnetic field on aircraft, the control of plasma flow field around aircraft can be realized. This has a broad prospect of applications in hypersonic aerodynamic control, aerothermal protection, and plasma distribution adjustment. Very recently, chemical reaction model and thermodynamic model were suggested to study the hypersonic magnetohydrodynamic control. However, the influence of different models and surface catalytic efficiency on hypersonic magnetohydrodynamic control are rarely analyzed in depth.

 In this study, a comparison of different chemical reaction models and the influence of surface catalytic efficiency are discussed. Three-dimensional (3D) nu-merical simulation method and program of extra magnetic field coupled with reentry plasma flow under the assumption of low magnetic Reynolds number are developed by solving 3D chemical non-equilibrium Navier-Stokes equations and Maxwell electromagnetic field governing equations. Based on this method, the influence of different gas component models, chemical reaction models, and surface catalytic efficiency on hypersonic magnetohydrodynamic control are analyzed. The results show that the conductivity of plasma, calculated by different gas component models and chemical reaction models, can be quite different from each other, thus can influence the accurate study on the structure of hypersonic magneto flow field as well as the aerothermal and aerodynamic characteristics. Based on the calculation conditions in this paper, the Park chemical model has advantages in the consistency and accuracy in numerical simulation. The magnetic thermal protection is greatly influenced by the surface catalytic efficiency and the correlation between the magnetic thermal protection and the surface catalytic efficiency is nonlinear and can be quite different in different region. As the surface catalytic efficiency increases, the influence of magnetic field on heat flux at stagnation point drops drastically, then increases slowly, which is a joint result of thermal conduction and chemical component diffusion. The influence of magnetic field on magnetohydrodynamic drag character is less affected by the surface catalytic efficiency. As the catalytic efficiency increases, the influence of magnetic field on magnetohydrodynamic drag character drops slowly.
Magnetocardiogram forward problem based on personalized three-dimensional heart-torso model
Authors: Xu Wei-Wei , Bai Ming-Zhu , Lin Qiang , Hu Zheng-Hui ,   College of Science, Zhejiang University of Technology, Hangzhou 310023, China,   Collaborative Innovation Center for Bio-Med Physics Information Technology, Zhejiang University of Technology, Hangzhou 310023, China
Published: December 2020

In order to simulate the distribution of magnetic field generated by cardiac electrophysiological activities, a three-dimensional (3D) computing framework of magnetocardiogram forward problem based on a finite element method (FEM) is proposed. First, the 3D heart-torso geometry model is established from the 3D reconstruction of magnetic resonance images. Then the modified FitzHugh-Nagumo (FHN) equation combined with 3D cardiac geometry is used to investigate the propagation of transmembrane potential (TMP). In the end, quasi-static Maxwell equations and 3D torso model are used to explore the propagation of the bioelectromagnetic field produced by TMP. In our calculation, the Galerkin finite element method is used. The results show that the FEM-model can simulate extracorporeal magnetic field. Further, numerical solutions of simplified models with the one-dimensional FHN equation and the straight wire are respectively consistent with the analytical solutions, which verifies the feasibility of the computing framework. In summary, this framework successfully simulates the cardiac TMP and extracorporeal magnetic field, which may conduce to the study of magnetocardiogram inverse problem.
Single-axial-mode Nd:YAG laser with precisely controllable laser pulse output time
Authors: Dai Shu-Tao , Jiang Tao , Wu Li-Xia , Wu Hong-Chun , Lin Wen-Xiong ,   Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou 350002, China,   China Aerodynamics Research and Development Center, Mianyang 621000, China
Published: December 2020

In recent years, high-energy single-axial-mode Q-switched lasers have been widely studied and applied because of their wide applications such as in nonlinear optics, laser spectroscopy and light detection and ranging (LIDAR). Many applications require a Q-switched pulse that has not only single axial mode but also can be synchronized with an external system. But two most commonly used methods (the build-up time reducing technique and ramp fire technique) are difficult to achieve single-axial mode operation. In this work, we apply the ramp-hold-fire technique to an injection-seeded Nd:YAG laser. The slave oscillator is a self-filtering unstable resonator (SFUR). The SFUR oscillator can achieve a smooth spatial profile TEM00 transverse mode. An RTP electro-optical crystal is adopted for intracavity phase modulator to modify the effective optical path length of the slave oscillator cavity. The seed-injection locking is realized by the ramp-hold-fire technique. The laser driver generates a pumping pulse. After a suitable time delay the driver is fired, a linear ramp voltage is applied to the RTP crystal. A photodiode detector monitors the interference signal. As soon as the interference peak is detected, the controlling electronics produces a stop signal. The ramp voltage on the RTP crystal is stopped and held at a fixed value. Then the Q-switch is fired at a set time, and finally single axial mode laser is demonstrated. Combining the advantages of intracavity phase modulation and Q-switch exact synchronization of the ramp hold fire technique, we obtain a narrow linewidth single-axial-mode laser pulse with precisely controllable output time. The laser is capable of generating 1064 nm pulse energy large than 50 mJ. The pulse build-up time is reduced by 31 ns to 48 ns. The pulse firing time is precisely controlled with jitter less than 1%. Then the frequency spectrum of the 1064 nm laser is measured with a commercial Fizeau wavemeter HighFinesse WS7. The multi-beam interference patterns of the pulse are shown to be smooth in the wavemeter. The wavelength is measured to be 1064.40416 nm and the linewidth is less than 0.5 pm which is limited by the instrument resolution. Meanwhile, the frequency stability is measured to be less than 0.1 pm (V-V) over 1700 pulses with a working frequency of 0.1 Hz.
In-situ infrared observation of molecularclustering near cooled surface
Authors: Chen Fang-Ying , Lan Zhong , Qiang Wei-Li , Lian Shi-Jun , Ma Xue-Hu ,   Institute of Chemical Engineering, Dalian University of Technology, Dalian 116012, China
Published: December 2020

For the saturated vapor condensation on the cooled surface, the evolution mechanism of vapor molecular in the transition zone between the bulk phase and the cooled surface is not clear yet. The molecular clustering model considers that the vapor molecules first form clusters in the gas phase before condensing on the cooled surface. However, it is difficult to observe the dynamic evolution of nanoparticles in the near-wall boundary layer, hence, the experimental verification about this model is not sufficient now. Based on the hydrogen bonded network formed inside the cluster, in this paper, the attenuated total reflection Fourier transform infrared spectroscopy is introduced to follow and detect the dynamic behavior of vapor molecules in the near-wall thin layer during the condensation process. The infrared spectra of the gas phase at different positions from the cooled surface during the condensation process are obtained. The experimental results directly verify the distribution of clusters in the near-wall region, indicating that clusters are the main units of vapor condensation and droplet growth. Moreover, the average cluster size n increases gradually along the direction near the cooled surface. Based on the hydrogen bond characteristics of clusters, the ethanol molecular clustering near the surface is also observed, which further verifies the rationality of this model. In addition, it’s found that the distribution region along the cooled surface of ethanol clusters during the process of condensation is smaller than that of water clusters under the same condition. This may indirectly indicate that the heat transfer boundary layer of ethanol vapor condensation is thinner than that of water vapor condensation, resulting in its weaker performance of heat transfer. This method, where we use the microstructures manufactured on the surface to regulate the distribution of clusters in the near-wall region, will provide a new insight into enhancing the process of steam condensation with non-condensable gas or efficient water capture from air.
Theoretical study of dissociation dynamics of HD+ and its quantum control with an intense laser field
Authors: Yao Hong-Bin , Jiang Xiang-Zhan , Cao Chang-Hong , Li Wen-Liang ,   Laboratory of New Energy and Materials, Xinjiang Institute of Engineering, Urumqi 830091, China
Published: December 2020

The dissociation dynamics of HD+ molecule in an intense field is investigated by using an accurate three-dimensional time-dependent wave packet approach. When the 790-nm laser pulse interacts with HD+ molecule, the lowest electronic 1sσ and 2pσ states are coupled. Due to the existence of the permanent electric dipole moment, the transitions in HD+ molecule involve the direct absorption of an odd and even number of photons, thereby opening different pathways for dissociation. The model of the photon-dressed states is presented to analyze the possible dissociation pathways of HD+ molecule. The laser-induced dissociation of HD+ molecule is mainly composed of the four pathways: the direct one-photon absorption, the net two-photon absorption, the direct two-photon absorption, and the direct two-photon absorption. To reveal the dissociation mechanism of HD+ molecule, the kinetic energy resolved spectra are calculated at the given laser intensities. It is found that the dissociation pathways are strongly dependent on laser intensity, especially for the net one-photon absorption dissociation and direct two-photon absorption dissociation. With further research, the dissociation pathways of HD+ are controlled by regulating the intensity of laser pulse. At a laser intensity of 4.0 × 1013 W/cm2, the kinetic energy resolved spectrum for the vibrational state ν = 3 includes the contributions from the net two-photon absorption dissociation and the direct two-photon absorption dissociation. For the vibrational state ν = 6, HD+ molecule is preferentially dissociated via the net one-photon absorption. However, the dissociation mechanism of HD+ molecule at the vibrational states ν = 3 and ν = 6 have significant changes as the laser intensity increases to 2.0 × 1014 W/cm2. For the vibrational state ν = 3, the branching ratio between the dissociation pathway of the net two-photon absorption and that of the direct two-photon absorption has a dramatic change with the increase of laser intensity. Compared with the kinetic energy resolved spectra at laser energy of 4.0 × 1013 W/cm2, the height of the dissociation peak from the net two-photon absorption decreases, and that of the direct two-photon absorption increases at laser intensity of 2.0 × 1014 W/cm2. For the vibrational state ν = 6, the dissociation process of the net one-photon absorption almost disappears at laser intensity of 2.0 × 1014 W/cm2, and it is replaced by the dissociation pathway of the direct two-photon absorption.
Rheological properties of ring and linear polymers under start-up shear by molecular dynamics simulations
Authors: Yang Jun-Sheng , Huang Duo-Hui ,   National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei 230026, China,   Computational Physics Key Laboratory of Sichuan Province, Yibin University, Yibin 644007, China
Published: December 2020

We analyze the structure and rheological properties of ring and linear polymers under shear byusing the non-equilibrium molecular dynamics simulation. The simulation results show that compared with the ring chains, the linear polymers do not present prominent stress over shoot phenomenon. Since the overshoot reflects the maximum flow-induced deformation of the polymer, this qualitative observation already implies that the ring experience less deformation than its linear precursor in simple shear flow. This is consistent with the recent experimental result. In order to further study the molecular mechanism of this phenomenon, the segmental structure and orientation angle distribution as a function of strain under the different Weissenberg numbers are given in this study. The weak overshoot of the stretching of the ring polymers proves that the weak shear thinning and peak strain are due to the weak deformation of the segment chain of the ring in the shear flow. The rheological properties of linear and ring system are extracted from the stress-strain curves, can be used further to analyze the data. The peak strain γmax as afunction of WiR follows a power-law with an exponent of 0.3 for linear polymer at WiR>1, however, for the ring system thepeak strain follows a power-law with an exponent of 0.1. The parameter ηmax/ηsteady is also the measure of the effective chain deformation at a steady state. The data show its progressive increase with WiR increasing, and follows a power-law with a scaling slop of 0.13 and 0.08 for linear and ring polymers, respectively. The peak stress σmax as a function of WiR is also extracted from stress-strain curve. The two investigated systems both obey the scaling law with an exponent of 0.5. The normalized steady-state shear viscosity obeys a shear thinning slop of –0.86 for the linear polymer, the ring polymer obeysa shear thinning slop of –0.4. According to the gyration tensor and orientation angle, the power-law relationship between stretching and orientation is also given in this work.
Total ionizing dose effects on innovative silicon-on-insulator static random access memory cell
Authors: Wang Shuo , Chang Yong-Wei , Chen Jing , Wang Ben-Yan , He Wei-Wei , Ge Hao ,   State Key Laboratory of Functional Materials for Informatics,  Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai 200050, China,   Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences, Beijing 100049, China
Published: December 2020

The static random access memory (SRAM), as a common and important high-speed storage module in modern digital circuit systems, plays an important role in improving the performances of electronic systems. The data about the total ionizing dose (TID) radiation effect of SRAM cell have not been rich in the literature so far. In this work, a novel 6-transistor SRAM cell (6T LB SRAM cell) based on L-type gate body-contact (LB) MOSFET device is designed and fabricated by 130nm silicon-on-insulator (SOI) process. The LB MOSFET follows the center-symmetric layout design of the SRAM cell, reducing the area by approximately 22% compared with the SRAM cell using the T-type gate MOSFET contact device (6T TB SRAM cell) of the same device size. The electrical performance difference between LB MOSFET and other devices is compared. Besides this, the variations of the leakage current and the reading static noise margin (RSNM) of SRAM cells based on different MOSFETs under various total ionizing doses are also investigated. The test results indicate that the LB MOS successfully suppresses the floating body effect (FBE), and that the drain-induced barrier lowing (DIBL) and drain-to-source breakdown voltage (BVds) characteristics are improved. The performance of this device is similar to that of TB MOS device, but due to the special body contact design, the former has an advantage of smaller area. Due to the use of the body contact device, the leakage current of the 6T LB SRAM cell is significantly smaller than that of the conventional floating device SRAM cell (6T FB SRAM cell), which has lower static power consumption. After 60Co-γ ray irradiation, the 700 krad(Si) radiation dose only increases the leakage current of 6T LB SRAM cell by 21.9%, which is better than 41.4% of 6T FB SRAM cell. In addition, the 6T LB SRAM cell has an RSNM value similar to that of the 6T TB SRAM cell, and this is 1.93 times higher than the that of 6T FB SRAM cell. The radiation experiment causes the butterfly curve of the 6T FB SRAM cell to be asymmetrically deformed, and the stability of the SRAM cell is deteriorated due to the TID effect. However, the test results show that when the radiation dose reaches 700 krad (Si), the RSNM value of the 6T LB SRAM cell is reduced only by 11.2%. Therefore, 6T LB SRAM cell has stable and reliable practical value.
Influence of different scattering medium on propagation characteristics to femtosecond laser pulses
Authors: Zhang Ke-Jin , Liu Lei , Zeng Qing-Wei , Gao Tai-Chang , Hu Shuai , Chen Ming ,   College of Meteorology and Oceanography, National University of Defense Technology, Nanjing 211101, China
Published: December 2020

During recent years, the filamentation of femtosecond laser in the atmosphere has contributed considerable interest to researchers. However, the actual atmosphere can result in different scattering medium, which are adverse to the application of filamentation in the atmosphere. In order to study the propagation of femtosecond laser in real scattering medium, the propagation of 800 nm femtosecond laser in ice cloud, water cloud, fog, aerosol and rainfall is simulated numerically. Combined with the theory of stratified medium model and Mie scattering theory, we constructed a scattering model with a changeable size distribution function in the nonlinear laser model. The results indicated that the different size distribution and phase state of particles have different influence on the propagation properties of the filaments. As the rainfall was dominated by large raindrops, the scattering on filament was the strongest, resulting in the lowest peak intensity and energy. In the case, the distribution of filament energy was extremely inhomogeneous, causing the shortest length of filament and generation of multi-filament. In the image of fluence distribution, a diffraction ring can be observed clearly in the rainfall but was blurred in other medium. The propagation properties of filaments in water cloud and fog were similar because of the same size distribution. However, due to the size of particle in fog was smaller than that in water cloud, the filaments had more higher energy and more concentrated distribution in fog. In addition, the scattering of ice particles was stronger than that of liquid droplets, so the energy of filament in ice cloud was lower than that in water cloud, resulting a reducing of the length and number of filaments in ice cloud. The size of aerosols was the smallest, which had the weakest influence on the filament. Accordingly, in the early of propagation, there had little perturbance on the filament and the beam was transmitting with a stable single filament, and results in the highest peak intensity and energy. With the propagation increasing, the accumulation of scattering attenuation produced the perturbation on filament at a position after the onset of filamentation.
Quasinormal mode analysis of extremely localized optical field in body-of-revolution plasmonic structures
Authors: Zhou Qiang , Lin Shu-Pei , Zhang Pu , Chen Xue-Wen ,   School of Physics and Center for Quantum Optical Science, Huazhong University of Science and Technology, Wuhan 430074, China
Published: December 2020

Surface plasmons in metallic nanostructures can confine the optical field within the region of subwavelength, even nanometer scale, and thus enhance the light-matter interaction and other physical processes, which will lead the plasmon optics to possess attractive applications in many areas. However, the " mode volume” often used to characterize field confinement in plasmonic structures is only defined phe-nomenologically and suffers ambiguity when applied to complex structures. In this work, we develop a theoretical method to characterize the field confinement based on quasi-normal mode analysis. We recognize the fact that a plasmonic resonance may result from many eigen-modes, which together contribute to the observed field confinement. An effective mode volume is introduced for quasi-normal modes and used to characterize the field confinement when the plasmonic resonance is dominated by a single quasi-normal mode. Two typical kinds of plasmonic structures are systematically examined, and the field confinement on the order of 10 nm3–100 nm3 is confirmed. In pursuit of the ultimate field confinement, we revisit the so-called " pico-cavity” formed by an atomistic protrusion in the nano gap of the particle-on-mirror configuration. The apparent hot spot is shown to have contributions from several quasi-normal modes. The dominant one exhibits a further squeezed mode volume compared with the scenario without the protrusion, but is still well above 10 nm3.
Experimental study on velocity of supersonic molecular beam based on microphone
Authors: Zhou Mao-Lei , Liu Dong , Qu Guo-Feng , Chen Zhi-Yuan , Li Min , Wang Yi-Zhou , Xu Zi-Xu , Han Ji-Feng ,   Key Laboratory of Radiation Physics and Technology of the Ministry of Education, Institute of Nuclear Science and Technology, Sichuan University, Chengdu 610064, China
Published: December 2020

The expansion and transportation of supersonic molecular beams is a complex process of molecular dynamics, and the related parameters are difficult to calculate accurately. Currently there is no rigorous theory to accurately predict the beam expansion process under specific valve conditions, and current researches are less concerned with the spatial evolution of supersonic molecular beam characteristics over long distance. In addition, time-of-flight mass spectrometry is not well suitable for supersonic molecular beam injection in the field of magnetic confinement fusion. Therefore, based on microphone measurements, the average velocities of several supersonic molecular beams (H2, D2, N2, Ar, He, CH4) in the process of free expansion and their evolutions in the far-field space (flight distance/nozzle diameter > 310) are studied in this work. The variations of velocity distribution with gas type, temperature, pressure and expansion distance are obtained. The results show that the velocities of H2, D2 and He beams account for only 54%, 60% and 68% of their ideal limit velocities, respectively, and their velocities decrease rapidly in the far-field space. The velocities of CH4, N2 and Ar beams are very close to their limit velocities, accounting for 85%, 92% and 99% respectively, and their velocities decrease slowly in the far-field space. And the results show that the velocities of the H2 and D2 beams increase with the source pressure, while the velocities of the other four molecular beams decrease slightly with the source pressure. And it is found that the velocity of supersonic beam without skimmer is negatively correlated with the square root of the molecular mass. For the effect of temperature on velocity, the results show that the velocities of H2 and D2 beams increase with the source temperature but are smaller than their limit velocities at given temperature, and the difference is larger for higher temperature. The results of this experiment provide basic data for controlling the parameters of the supersonic molecular beam by adjusting the temperature and pressure of the gas source, which will contribute to the application of supersonic molecular beams in fusion reactor fueling technology. And this study will contribute to further exploration of the evolution of supersonic molecular beam properties in the far-field space.
A mobile three-dimensional active vibration isolator and its application to cold atom interferometry
Authors: Chen Bin , Long Jin-Bao , Xie Hong-Tai , Chen Luo-Kan , Chen Shuai ,   Hefei National Laboratory for Physical Sciences at Microscale, Department of Modern Physics,University of Science and Technology of China, Hefei 230026, China,   CAS Center for Excellence in Quantum Information and Quantum Physics, Shanghai 201315, China
Published: December 2020

Vibration noise has an influence on the sensitivity and stability for many precision instruments, especially for atom interferometers. In this paper, a mobile three-dimensional active vibration isolation system is established for portable atom interferometer that is effectively isolated from the ground vibration, thereby improving the sensitivity of the portable atom interferometer, and can be deployed and recovered to working state rapidly. With the home-developed integrated feedback algorithm, this system achieves a good vibration suppression in a wide frequency range in three directions. It suppresses the ground vibration by three orders of magnitude in the vertical direction, and one order of magnitude in the horizontal direction. In a frequency range less than 10 Hz which the atom interferometer is sensitive to, the vibration noise is suppressed to 4.8 × 10–9 m/s2/Hz1/2 in the vertical direction and to 2.7 × 10–7 m/s2/Hz1/2 in the horizontal direction. The influence of vibration noise on the sensitivity of the atom interferometer reaches to 2 μGal/Hz1/2, which is reduced by two orders of magnitude compared with the result without our system.
Theoretical study of density functional of confined CO oxidation reaction between bilayer graphene
Authors: Cui Shu-Wen , Li Lu , Wei Lian-Jia , Qian Ping ,   Department of Physics and Information Engineering, Cangzhou Normal University, Cangzhou 061001, China,   State Key Laboratory of Nonlinear Mechanics (LNM), Institute of Mechanics, Chinese Academy of Science, Beijing 100190, China,   School of Mathematics and Physics, University of Science and Technology Beijing, Beijing 100083, China
Published: December 2020

Graphene is a two-dimensional (2D) crystal of carbon atoms packed in a honeycomb lattice. Because of this unique structure, it shows a number of intriguing properties. Interface between neighboring 2D layers or between 2D overlayers and substrate surfaces provides confined space for chemical process. The interlayer spacing between bilayer graphenes of van der Waals material is expected to modify the properties of atoms and molecules confined at the atomic interfaces. In this paper, the carbon monoxide (CO) and oxygen (O) in bilayer graphene are studied by density functional theory (DFT). The quantitative relationship between the interlayer spacing of bilayer graphene (d) and the reaction energy barrier (\begin{document}$ {{E_{\rm{a}}}} $\end{document}) is obtained. Five values of d between 4.7 Å and 5.9 Å are used. The calculated results show that the total energy of the initial state, the transition state, the final state system and the reaction barrier are sensitive to the variation of the interlayer distance: the reaction barrier increases gradually with interlayer distance decreasing. The calculated energy barrier is 1.13 eV when the interlayer distance is 4.7 Å, while the energy barrier is 0.39 eV when the interlayer distance is 5.9 Å. It is also found that adsorption energy between O and graphene at the top site and the bridge site increase gradually with interlayer distance decreasing. Therefore, the atomic-level regulation of the reaction barrier can be achieved by changing the interlayer spacing of bilayer graphene. The charge density difference shows that when the distance between two layers of graphene is small, there is an obvious charge accumulation between C atoms in transition state O—C=O and C atoms in the upper or lower layer of graphene. This results in sp orbital hybridization, which leads the interaction between two C atoms to be enhanced. It is difficult to form a weak O—C bond of transition state O—C=O with O atoms adsorbed on graphene because of a binding force which exists in the z-axis direction. The DFT calculation of CO oxidation reaction barrier can be reduced by adjusting the spacing of bilayer graphene, which provides a theoretical support for the application of graphene and the preparation of new carbon-based intercalated composites.
Surface-enhanced Raman scattering of subwavelength metallic structures
Authors: Qin Kang , Yuan Lie-Rong , Tan Jun , Peng Sheng , Wang Qian-Jin , Zhang Xue-Jin , Lu Yan-Qing , Zhu Yong-Yuan ,   Collaborative Innovation Center of Advanced Microstructures, National Laboratory of Solid State Microstructures, College of Engineering and Applied Sciences, Nanjing University, Nanjing 210093, China
Published: December 2020

Surface-enhanced Raman scattering (SERS) makes the Raman signals, as fingerprints of different vibration modes of chemical bonds, significant in practical applications. Two main mechanisms, chemical and physical, are attributed to the SERS of molecules adsorbed on metals. The physical mechanism plays a major role in SERS, which is the focus of our paper. Recent SERS systems are mostly based on dimer structures, i.e. nanoparticle pairs, of noble metals. Large amplification of electrical field occurs in the gap of a dimer structure compared with a single nanoparticle. The above gap positions are called as " hot spots” of SERS. In addition, the reproducibility and reliability of SERS substrates are also important for practical applications. Here we use periodical subwavelength metallic structures to meet such needs, and develop other kinds of electrical field enhancement mechanisms. We present the electrical field enhancement of the band-edge mode of surface plasmon polariton, gap plasmon polariton mode, as well as their coupling mode. We choose one-dimensional subwavelength metallic structures to clarify the physical mechanism. Our purpose is to develop subwavelength metallic structures with even and intensive " hot spots”, serving as ultrasensitive solid-state SERS substrates with excellent reproducibility and reliability.
Eavesdropping and countermeasures for backflash side channel in fiber polarization-coded quantum key distribution
Authors: Chen Yan-Hui , Wang Jin-Dong , Du Cong , Ma Rui-Li , Zhao Jia-Yu , Qin Xiao-Juan , Wei Zheng-Jun , Zhang Zhi-Ming ,   Guangdong Provincial Key Laboratory of Nanophotonic Functional Materials and Devices, Key Laboratory of Quantum Engineering and Quantum Materials, South China Normal University, Guangzhou 510006, China,   Guangdong Polytechnic Institute, Guangzhou 510091, China
Published: December 2020

Nowadays, the practical security of quantum key distribution (QKD) is the biggest challenge. In practical implementation, the security of a practical system strongly depends on its device implementation, and device defects will create security holes. The information leakage from a receiving unit due to secondary photon emission (backflash) is caused by a single-photon detector in the avalanche process. Now studies have shown that the backflash will leak the information about time and polarization and the eavesdropping behavior will not generate additional error rate in the communication process. An eavesdropping scheme obtaining time information by using backflash is proposed. Targeting this security hole for backflash leaking polarization information, an eavesdropping scheme for obtaining polarization information by using backflash is proposed in free-space QKD; however, it has not been reported in fiber QKD. In this study, the eavesdropping scheme and countermeasures for obtaining information by using backflash in fiber polarization-coded QKD is proposed. Since the polarization state of the fiber polarization-coded QKD system is easy to change, the scheme is proposed based on the time-division multiplexing polarization compensation fiber polarization-coded QKD system. In theory, the eavesdropper in this scheme obtaining the key information by using the backflash is theoretically deduced, and corrects the polarization change of the backflash by time-division multiplexing polarization compensation method, thus obtaining the accurate polarization information. The probability of backflash in the fiber polarization-coded QKD is measured to be 0.05, and the information leakage in the proposed eavesdropping scheme is quantified. The lower limit of the information obtained by the eavesdropper is 2.5 × 10–4. Due to the fact that the polarization compensation process increases invalid information in actual operation, the information obtained by the eavesdropper will be further reduced, thus obtaining the lower limit of information leakage. The results show that the backflash leaks a small amount of key information in a time-multiplexed polarization-compensated fiber polarization-coded QKD system. The wavelength characteristics of the backflash can be utilized to take corresponding defense methods. Backflash has a wide spectral range, and the count of backflash has a peak wavelength. So, tunable filters and isolators can be used to reduce backflash leakage, thereby reducing the information leakage.