bluuebunny/crossref_metadata_2025 huggingface dataset:
Application of photon-added two-mode squeezed vacuum states to phase estimation based on Mach-Zehnder interferometer
Authors: Wang Shuai , Sui Yong-Xing , Meng Xiang-Guo ,   School of Mathematics and Physics, Jiangsu University of Technology, Changzhou 213001, China,   School of Physics Science and Information Technology, Liaocheng University, Liaocheng 252059, China
Published: December 2020

Quantum metrology is to estimate accurately the value of an unknown parameter with the assistance of the quantum effects, in order to break through the standard quantum limit, even reach the Heisenberg limit. In this work, we study the performance of a general photon-added two-mode squeezed vacuum state that is taken as a detection state of a Mach-Zehnder interferometer. Based on quantum Fisher information, within the constraint on the total mean photon number, symmetric and asymmetric photon addition cannot improve the ultimate phase sensitivity. However, for a given initial squeezing parameter, on this occasion, the symmetric and asymmetric photon addition can improve the ultimate phase sensitivity. Compared with the asymmetric photon-added two-mode squeezed vacuum state, the symmetric one can well improve the ultimate phase sensitivity. This may be because it is always better to implement the symmetric photon addition rather than the asymmetric one in order to increase the mean photon number of the resulting state. On the other hand, via parity detection, the symmetric and asymmetric photon-added two-mode squeezed vacuum state can indeed improve the phase sensitivity of a Mach-Zehnder interferometer for a given initial squeezing parameter. Based on the parity detection, within a constraint on the mean photon number, although the two-mode squeezed vacuum state can give the better phase sensitivity at the optimal phase shift (φ = 0), the phase sensitivity offered by the symmetric and asymmetric photon-added two-mode squeezed vacuum states are both more stable around φ = 0 than by the two-mode squeezed vacuum state. In addition, we show that for the symmetric photon-added two-mode squeezed vacuum state, parity detection is an optimal detection only when the optimal phase shift approaches to zero. When the phase shift slightly deviates from zero, the parity detection is not an optimal detection scheme. Finally, for all values of the phase shift, our results also clearly show that the parity detection is not an optimal detection scheme for the asymmetric photon-added two-mode squeezed vacuum state serving as an interferometer state.
Research progress of analogical gravitation on optical metamaterial chips
Authors: Sheng Chong , Liu Hui , Zhu Shi-Ning ,   Collaborative Innovation Center of Advanced Microstructures, State Key Laboratory of Solid State Microstructures, School of Physics, Nanjing University, Nanjing 210093, China
Published: December 2020

Optical metamaterial is a kind of artificially designed microstructured material. Its occurrence breaks the localization of traditional material design thinking and provides a new paradigm for artificially controlling electromagnetic waves on a micro-nano scale, especially realizes optical properties beyond conventional materials in nature. Furthermore, metamaterial has the ability to couple electromagnetic waves into the sub-wavelength regime, meeting the high-speed development of modern science and technology, which puts forward new requirements for high performance, miniaturization and integration of optical components. Therefore, optical chips based on metamaterials bring many encouraging applications such as in perfect imaging that breaks through the diffraction limit, multifunctional integrated optics, etc. In addition, metamaterial photonic chips can also simulate some phenomena in general relativity, especially exploring some phenomena that have not been experimentally proven. This review paper briefly introduces the study of analogical gravitation based on different kinds of photonic chips on the basis of metamaterials. In the end, there present the summary and outlook about the current development, advantages and challenges of this field.
Reciprocal waveguide coupled mode theory
Authors: Chen Yun-Tian , Wang Jing-Wei , Chen Wei-Jin , Xu Jing ,   School of Optical and Electronic Information, Huazhong University of Science and Technology, Wuhan 430074, China,   Wuhan National Laboratory of Optoelectronics, Huazhong University of Science and Technology, Wuhan 430074, China
Published: December 2020

Mode coupling is a common phenomenon in waveguides. The mode coupling among different guided modes in fiber-optic communication can cause crosstalk, and the mode coupling of guided mode and radiated mode can reduce the power of the guided mode. Application of mode coupling can guide the design of optical devices such as couplers and beam splitters with specific functions, which have been widely used in fiber optic communication and fiber sensing. So it is important to analyze how waveguide modes are coupled. The coupled-mode theory is a common method of studying mode coupling in waveguides. It provides not only an intuitive picture of how the photonic modes are hybridized, but also a quantitative assessment of how the hybridization among those relevant modes evolves. In recent years, non-Hermitian waveguides, represented by parity-time symmetrical structures, have become a research hotspot. However the conventional coupled-mode theory no longer works in this case. In this review, we briefly summarize the development history of coupled-mode theory and introduce the representative work in reciprocal waveguide coupled-mode theory in detail. Then the relationship among several coupled-mode theories is analyzed and their applications are briefly introduced.
Influence of ablation on energy deposition in polymer material under irradiation of intense pulsed ion beam
Authors: Zhang Shi-Jian , Yu Xiao , Zhong Hao-Wen , Liang Guo-Ying , Xu Mo-Fei , Zhang Nan , Ren Jian-Hui , Kuang Shi-Cheng , Yan Sha , Gennady Efimovich Remnev , Le Xiao-Yun ,   School of Physics, Beihang University, Beijing 100191, China,   Beijing Advanced Innovation Center for Big Data-based Precision Medicine, Beihang University, Beijing 100191, China,   Beijing Key Laboratory of Advanced Nuclear Energy Materials and Physics, Beihang University, Beijing 100191, China,   National Research Tomsk Polytechnic University, Tomsk 634050, Russia,   Institute of Heavy Ion Physics, Peking University, Beijing 100871, China
Published: December 2020

Short-pulse length and high-power density, intense pulsed ion beam (IPIB) has been widely studied in material processing during past decades. Ablation effect plays a great role in the interaction between IPIB and material and may affect the energy deposition of IPIB, thus further influencing the beam application and diagnostics. Therefore, the investigation of ablation effect on energy deposition of IPIB in the irradiated material is of great significance for its applications and diagnostic techniques. In this work, experiments on the IPIB irradiation are carried out on the BIPPAB-450 accelerator at Beihang University. Its maximum accelerating voltage is 450 kV, peak current density is 150 A/cm2, energy density is 1.5–1.8 J/cm2 and pulse duration (FWHM) is 80 ns. Polymer materials which have low thermal conductivity, low decomposition temperature and thus yield to ablation under low beam density, such as polycarbonate (PC), polyvinyl chloride (PVC) and polymethyl methacrylate (PMMA), are chosen in the present research. The 304 stainless steel is used for calorimetric beam diagnostics and comparative analysis. Energy deposition in polymer material and 304 stainless steel are obtained by high infrared imaging diagnostics. It is revealed that the distributions of energy deposition in these two kinds of materials differ from each other obviously. The highest energy density deposited in the 304 stainless steel appears in the center of the irradiated area where focused is the beam with a higher energy density. However, the central energy density in polymer material turns out to be lower than the surrounding area, indicating that a large portion of the ion beam is prevented from reaching the target. Meanwhile, the simulation based on the finite element method is carried out for the thermal filed distribution and evolution under the IPIB irradiation. The simulation result indicates that the strong ablation can be generated on the target surface since the highest temperature caused by IPIB irradiation is much higher than its decomposition temperature. According to the results of experiments and simulation, the polymer material can start to be ablated at the initial stage of IPIB irradiation which will consume partial energy and the products of ablation may act as shielding to block the energy deposition in the same pulse.
Dielectric, ferroelectric and high energy storage behavior of (1–x)K0.5Na0.5NbO3–xBi(Mg0.5Ti0.5)O3 lead free relaxor ferroelectric ceramics
Authors: Du Jin-Hua , Li Yong , Sun Ning-Ning , Zhao Ye , Hao Xi-Hong ,   Inner Mongolia Key Laboratory of Ferroelectric-related New Energy Materials and Devices, Inner Mongolia University of Science and Technology, Baotou 014010, China,   Industrial Technology Research Institute, Inner Mongolia University of Science and Technology, Baotou 014010, China,   School of Chemistry and Chemical Engineering, Inner Mongolia University of Science and Technology, Baotou 014010, China
Published: December 2020

Lead-free dielectric ceramics with high energy-storage density and efficiency are ideal energy materials for sustainable development of the enery resource. In this paper, (1–x)K0.5Na0.5NbO3–xBi(Mg0.5Ti0.5)O3 ((1–x)KNN-xBMT, x = 0.05, 0.10, 0.15, 0.20) lead-free relaxor ferroelectric ceramics are prepared by the traditional solid-state method. The effects of BMT on the phase structure, microstructure, dielectric properties and energy storage behavior of KNN based ceramics are studied. With the increase of BMT content, the crystal structures of (1–x)KNN-xBMT ceramics gradually change from orthorhombic to pseudo-cubic phase, and transform into cubic phase finally. The addition of BMT can suppress grain growth of the ceramics, resulting in the average grain size decreasing from 850 to 195 nm when x increases from 0.05 to 0.20. Dielectric properties exhibit that the Curie temperature decreases with BMT content increasing, and dielectric peak at Curie temperature is broadened due to the addition of BMT. In addition, ferroelectric properties demonstrate that the addition of BMT reduces the remnant polarization (Pr) and coercive field (Ec) of the ceramics. The results indicate that (1–x)KNN-xBMT ceramics transform from ferroelectric to relaxor ferroelectric phase. Based on the calculation of hysteresis loop, the best energy storage performance is obtained at x = 0.15, of which the recoverable energy storage density (Wrec) and the energy storage efficiency (η) are 2.25 J·cm–3 and 84% at its dielectric breakdown strength of 275 kV·cm–1. Meanwhile, the ceramic with x = 0.15 exhibits good stability in a frequency range of 1–50 Hz, with an energy density variation of less than 5%, and temperature stability in a range of 25–125 ℃ with change of less than 8%. Moreover, based on direct measurement, the energy storage density (Wdis) of the ceramic with x = 0.15 is 1.54 J·cm–3, and the discharge time is only 88 ns. The research shows that (1–x)KNN-xBMT ceramics have a wide application prospect in the field of environmentally friendly capacitors with high energy storage density.
Tuning optical force of dielectric/metal core-shell placed above Au film
Authors: Zhang Jia-Chen , Yu Wei-Xing , Xiao Fa-Jun , Zhao Jian-Lin ,   Shaanxi Key Laboratory of Optical Information Technology, School of Physical Science and Technology, Northwestern Polytechnical University, Xi’an 710129, China,   CAS Key Laboratory of Spectral Imaging Technology, Xi’an Institute of Optics and Precision Mechanics of CAS, Xi’an 710119, China
Published: December 2020

Manipulating the core-shell structure with the optical force has been extensively studied, giving birth to applications such as particle sorting, biomarkers and drug delivery. Tailoring the optical force exerted on the core-shell above the metallic film remains unexplored, despite the obvious benefits for both fundamental research and applications including strong coupling, surface enhanced spectroscopy, nanolaser, and nanoscale sensing. In this work, we systematically investigate the optical force exerted on a dielectric/metal core-shell above a gold film by utilizing the Maxwell stress tensor formalism. It is found that at the present gold substrate, the optical force on the core-shell can be one order of magnitude larger than that on the individual core-shell due to the strong coupling between the core-shell and the gold film. Interestingly, the direction of the optical force can be reversed from positive to negative by distributing the local field from the upside of core-shell to the structure gap through changing the excitation wavelength. Furthermore, we demonstrate that the magnitude and peak wavelength of the optical force can be well controlled by altering the structure gap, the size and refractive index of the core. More specifically, it is found that the coupling strength between the core-shell and the gold film decreases with the gap size increasing. As a result, we observe the blue shift of bonding mode and the decrease of local field in the gap, which leads the force peak wavelength to be blue-shifted and the force peak magnitude to decrease, respectively. Also, by increasing the radius and refractive index of the core, a red shift of force peak is accompanied with the red shift of the bonding mode. In addition, the force peak magnitude follows the same trend as the total local field enhancement factor when the radius and refractive index of the core change. We hope that our results open the way to control the cavity size of particle on film structure, which would be beneficial for tailoring the light matter interaction even down to single molecular level and promises to have the applications in novel functional photonic devices.
Risk transmission between banks based on time-varying state network
Authors: Qiu Lu , Huang Guo-Yan ,   School of Finance and Business, Shanghai Normal University, Shanghai 200234, China,   School of Business, East China University of Science and Technology, Shanghai 200237, China
Published: December 2020

Aiming at the state transition between bank networks, we propose a time-varying state network model. In this model, we classify the bank networks in each time period by the kmeans method, and use directed minimum spanning tree(DMST) method to describe the topological structure of each kind of bank network. We also construct a time-varying bank state network by the planar maximally filtered graph(PMFG) method. The state network can be used to find the source of bank risk and conduct the time-varying analysis. We put into the model the inter-bank lending data of 15 listed Chinese commercial banks from the fourth quarter of 2007 to the first quarter of 2019. The results show that the short-term continuity jump between the bank states can effectively describe the occurrence of financial crisis. For example, before and after the global financial crisis in 2008, there was a short-term jump between two states. From the “money shortage” in 2013 to the stock market crash in 2015, there were four short-term jumps between states. At the same time, the outgoing degree of each directed bank state network is directly proportional to the contagion effect, and the incoming degree is inversely proportional to the steady degree of the risk faced by the bank. The sequential bank state network has the memory characteristic, which can provide the central bank for decision basis to prevent the systematic risk.
Helicon wave damping coefficient of Chinese fusion engineering testing reactor plasma
Authors: Li Xin-Xia , Li Guo-Zhuang , Liu Hong-Bo ,   School of Nuclear Science and Technology, University of South China, Hengyang 421001, China,   Institute of Plasma Physics, Chinese Academy of Sciences, Hefei 230031, China
Published: December 2020

The Chinese fusion engineering testing reactor (CFETR), complementing the ITER facility, is aimed at building up the science and technology base for the prototype of fusion power plant (PFPP). Based on the dispersion relation of fast wave, the analysis of the plasma dispersion function \begin{document}$ Z(\xi )$\end{document} is performed and a numerical solution of \begin{document}$ Z(\xi )$\end{document} is obtained. As the consequence, the dependence of helicon wave damping factor G on the plasma parameters and that on the wave properties are both achieved. The results show that an off-axis power deposition of the wave along the device radius can be achieved under the condition of plasma discharge on CFETR tokamak. Moreover, by calculating the ratio of the electron Alfven damping in the ion cyclotron range of frequencies to the electron Landau damping, we find that the electron Alfven damping is dominant at lower wave frequencies. With the wave frequency increasing, the electron Alfven damping remains unchanged while the Landau damping increases rapidly. With the discharge parameters of CTETR hybrid mode, the electron Landau damping proves to be dominant. Moreover, the off-axis power deposition and current drive profiles are produced. It is shown that the helicon wave damping factor increases with wave frequency increasing and it is closely related to the parallel refractive index of the injected wave spectrum, the plasma density, and plasma temperature. Significant off-axis power deposition and current drive are shown in CTETR hybrid mode operation, and the current drive efficiency reaches 50 kA/MW for helicon wave with a frequency of 800 MHz. Numerical simulation performed on the GENRAY/CQL3d shows a good consistence with the experimental results.
Sliding and accumulation characteristics of loose materials and its influencing factors based on discrete element method
Authors: Cheng Hao , Han Pei-Feng , Su You-Wen ,   School of Civil Engineering and Architecture, Southwest University of Science and Technology, Mianyang 621010, China,   Research Center on Mountain Torrent and Geologic Disaster Prevention, Ministry of Water Resources, Wuhan 430010, China
Published: December 2020

Loose materials has loose structure and is the main source of geological disasters such as collapses and landslides. Its hazard range is greatly affected by factors such as stone content and slope. Traditional studies on the sliding and accumulation characteristics of loose materials were mostly macro or qualitative analysis. There is little research on the micro internal motion mechanism. In the present study, discrete element method was used to quantitatively analyze the influence of stone content and slope variation on the characteristic values of loose particles such as stroke, accumulation width, maximum thickness, accumulation area, accumulation contour shape, accumulation volume, static accumulation angle and the cumulative mass. In the meanwhile, the movement and accumulation characteristics of the loose materials during the catastrophe process were explored from the aspect of energy and contact force of the particles, so as to reveal the interaction mechanism between the particles. The results showed that: When the stone content increased in the range of 0 to 70%, the stroke, accumulation width and accumulation area increased firstly and then decreased, and in the end the cumulative mass decreased. As the slope increased from 30° to 65°, the stroke, accumulation width, accumulation area and accumulation mass increased; the maximum thickness decreased approximately linearly, while the static accumulation angle had a decrease similar to quadratic function. In addition, there was a critical distance Lc for the volume share of coarse and fine particles in the accumulation area. When the distance from the toe line was L < Lc, the fine particles were larger than the volume of the coarse particles; when L > Lc, the fine particles were smaller than the volume occupied by coarse particles.
Preparation and properties of spodumene/silicon carbide composite ceramic materials
Authors: Lu Yuan-Yuan , Lu Gui-Hua , Zhou Heng-Wei , Huang Yi-Neng ,   Xinjiang Laboratory of Phase Transitions and Microstructures in Condensed Matters, College of Physical Science and Technology, Yili Normal University, Yining 835000, China,   National Laboratory of Solid State Microstructures, School of Physics, Nanjing University, Nanjing 210093, China
Published: December 2020

Silicon carbide (SiC) is widely used due to the lower coefficient of thermal expansion (CTE), high thermal conductivity and excellent mechanical properties. However, the self-diffusion coefficient of SiC relative to that of oxide ceramics is very low, it is difficult to sinter at lower temperature. The β-spodumene has ultra low or even negative thermal expansion coefficient combined with good thermal and chemical durability, which melts at 1423 ℃. Accordingly, the present study focuses on the use of β-spodumene as a flux at lower sintering temperature and the preparation of lower CET composite ceramics. The effects of spodumene on the sintering behavior, phase relations, thermal expansion and mechanical properties of spodumene/silicon carbide composites are discussed.

A high pure β-spodumene LiAlSi2O6 compound with nearly zero thermal expansion coefficient is synthesized via solid phase sintering. Spodumene/silicon carbide composites are fabricated by the adding 25, 30, 35 and 40 mass% synthesized β-spodumene powder to 75, 70, 65 and 60 mass% α-SiC matrix, respectively. Both β-spodumene and SiC are fabricated by conventional pressureless liquid sintering technique, and the batches are uniaxially pressed into discs and rectangular bars, then sintered at 1550 ℃ for 2 h in an Ar atmosphere.

The results show that the SiC and β-spodumene do not react during sintering, and the β-spodumene changes from tetragonal phase into hexagonal phase, the cell volume has a considerable shrinkage. A certain amount of liquid phase can help to enhance the density, improve Young’s modulus and promote the sintering behavior of SiC. When the feedstock contains 35% β-spodumene, the Young’s modulus reaches to (204.2 ± 0.5) GPa. Excess porosity is formed when liquid phase is too much during sintering, The Young's modulus of the sample 40SP is (119.6 ± 0.5) GPa. It is determined that the Young’s modulus of these materials are affected by porosity and internal microcracks. This study indicates that the content of β-spodumene and porosity are the dominant factors to control the CET of composites, but the porosity has a stronger effect. Besides, the microcracks, which are formed by the interaction of various internal stresses, are also an impotant factor. The materials with nearly zero thermal expansion are developed in a lower temperature range from –150 ℃ to 25 ℃, the spodumene content in the most stable composite reaches 40 mass%, and the CET of composite is close to that of Si (α25 ℃ = 2.59 × 10–6 ℃–1) in a temperature range of 25–480 ℃.
Light-field assisted spin-polarized transport properties in magnetic-electric barrier structures
Authors: Li Chun-Lei , Xu Yan , Zheng Jun , Wang Xiao-Ming , Yuan Rui-Yang , Guo Yong ,   College of Elementary Education, Capital Normal University, Beijing 100048, China,   College of Mathematics and Physics, Bohai University, Jinzhou 121013, China,   Middle School Affiliated to China University of Geosciences, Beijing 100083, China,   Department of Physics, Capital Normal University, Beijing 100048, China,   State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, China,   Collaborative Innovation Center of Quantum Matter, Beijing 100084, China
Published: December 2020

Based on the Floquet theory and transfer-matrix method, We investigated the influence of light-field on the spin-polarized transport properties for electrons tunneling through two kinds of magnetic-electric barrier structures (the \begin{document}$\delta$\end{document}-doped magnetic-barrier can be realized in experiments by depositing two ferromagnetic stripes on top and bottom of a semiconductor heterostructure and the light-field can be realized by placing a hemispherical silicon lens on the back surface of the semiconductor substrate). Transport properties result from the interaction of electrons with the light-field by means of photon absorption and emission. It is found that the light-field can greatly affect the transmission probabilities as well as the corresponding polarizations. The distance between the adjacent peaks and the number of the transport peaks can be controlled by adjusting the frequency and the amplitude of the light-field, respectively. It is shown that a significant spin-polarization effect can be induced by such light-field in the kind of antisymmetric magnetic barrier structure (\begin{document}$B_{1}=-B_{2}$\end{document}) and the light-field can greatly change the spin-polarization effect in the kind of symmetric magnetic barrier structure (\begin{document}$B_{1}=B_{2}$\end{document}). When the frequency of the light-field increases, the spin-polarization shifts toward the low-energy end and gradually increases. These remarkable properties of spin polarization may be beneficial for the devising tunable spin filtering devices.
Grain and grain boundary characteristics and phase transition of ZnS nanocrystallines under pressure
Authors: Wang Chun-Jie , Wang Yue , Gao Chun-Xiao ,   College of Engineering, Bohai University, Jinzhou 121013, China,   College of New Energy, Bohai University, Jinzhou 121013, China,   State Key Laboratory of Superhard Materials, Jilin University, Changchun 130012, China
Published: December 2020

In this paper, the grain and grain boundary characteristics and mechanisms of phase transition (from wurtzite to zinc-blende to rock-salt phase structure) of ZnS nanocrystallines are investigated via in situ impedance measurement under pressure up to 29.8 GPa. It should be noted that there are two semiarcs can be found from the modulus plots of ZnS under different pressures. The semiarc in high frequency region represents the grain characteristic, and another one in low frequency region refers to the grain boundary characteristic. The former decreases gradually with pressure increasing and the latter shows an opposite trend. This fact indicates that the effect of grain characteristic becomes weaker and weaker, and the role of grain boundary characteristic is just on the contrary. The grain resistance and grain boundary resistance of ZnS nanocrystalline are also studied. In the low pressure region, both resistances increase with different increment rate with pressure increasing, which can be attributed to the enhanced ability of trap charge carriers due to the small size effect of nanoparticles. In addition, two discontinuous points (about 11 and 15 GPa) can be observed in both resistance curves, corresponding to the points of phase transition from wurtzite to zinc-blende to rock-salt phase structure. With pressure increasing, both resistances decrease gradually until 21 GPa, and this point corresponds to the end of transition from zinc-blende to rock-salt phase structure. Their consequent variations are different, grain boundary resistance gradually decreases with the pressure increasing, while the grain resistance is almost a constant. Additionally, the relaxation frequency, as an intrinsic characteristic, is not affected by the geometrical parameters. According to the linear relation between the grain boundary relaxation frequency and pressure in the pressure range of phase transformation, the mechanism of structure transition from wurtzite to zinc-blende to rock-salt phase structure is also discussed in detail. Based on the investigations, the in situ impedance spectroscopy can not only be used to accurately measure the grain and grain boundary characteristics, but also provide information for studying the phase transformation under pressure.
Blood pressure estimation based on heart sound signals
Authors: Cheng Xie-Feng , Dai Shi-Cheng , Zhao Peng-Jun ,   College of Electronic and Optical Engineering, Nanjing University of Posts and Telecommunications, Nanjing 210023, China,   Pediatric Cardiology, Xin Hua Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai 200092, China
Published: December 2020

Cardiovascular disease, especially hypertension, has become one of the biggest killers of human life and health. Therefore, early detection and prevention of cardiovascular diseases are of great significance for people’s health. In this paper, we explore the relationship between aortic valve heart sound signal and blood pressure, and propose a method of non-invasively estimating blood pressure based on heart sound signals. First, according to the relationship between blood pressure and the heart sound signal, both the time interval between the peak point of the first heart sound and that of the second heart sound and the kurtosis of the second heart sound are extracted as features. Then the time interval between the first heart sound and the second heart sound, and the kurtosis of the second heart sound are linearly fitted to the measured blood pressure. Finally, according to the linear relationship between heart sound and blood pressure, a blood pressure evaluation formula based on the heart sound is established. The experimental results show that the time interval between the peak point of the first heart sound and that of the second heart sound, and the kurtosis of the second heart sound can be used as the characteristic parameters of blood pressure evaluation, which have a good linear relationship with blood pressure. The goodness of fit is 0.801 and 0.765, separately. The average error between the blood pressure calculated from the blood pressure calculation formula and the blood pressure measured by a commercial electronic sphygmomanometer is less than 5 mmHg, and the standard deviation is less than 8 mmHg. For hypertensive patients, the time interval between the peak point of the first heart sound and the second heart sound is shortened, and the kurtosis of the second heart sound is increased, which is a typical feature of heart sounds in patients with hypertension. Compared with the traditional blood pressure calculation method, the blood pressure assessment method proposed in this paper only needs to collect heart sound signals to effectively assess the blood pressure. The method is convenient to operate and can be used for continuously monitoring the blood pressure, and is especially suitable for monitoring the blood pressures of infants, disabled patients with limbs, and disabilities in certain medical environments.
Density distribution characteristics of fluid inside vortex in supersonic mixing layer
Authors: Guo Guang-Ming , Zhu Lin , Xing Bo-Yang ,   College of Mechanical Engineering, Yangzhou University, Yangzhou 225127, China,   School of Aeronautics and Astronautics, Shanghai Jiao Tong University, Shanghai 200240, China
Published: December 2020

Based on the large eddy simulation, the boundary of a vortex and the coordinates of its core are both obtained by using the Lagrangian coherent structure method and the location extraction method of the vortex core, and thus the method of representing fluid density inside a vortex is proposed. The density distribution characteristics of fluid inside the vortex in a supersonic mixing layer are revealed by analyzing the changes in density of the fluid inside a vortex under different conditions (e.g. spatial size of the vortex, compressibility of the supersonic mixing layer, and merging process of the two paired vortices) as follows. For the weak and medium compressive supersonic mixing layers, the density distribution of the fluid inside a vortex is symmetrical about both the flow direction (x-axis) and longitudinal direction (y-axis), the fluid density at the vortex core is lowest while it is highest at the vortex boundary, and fluid density increases monotonically and nearly uniformly along the ray connecting the vortex core and the vortex boundary. For the strongly compressible supersonic mixing layer, however, the density distribution of the fluid inside the vortex is no longer symmetrical about any flow direction and moreover it shows the fluctuation characteristics of fluid density distribution. With the increase of the spatial size of a vortex and the compressibility of a supersonic mixing layer, the fluid density at the vortex core decreases (the maximum reduction is about 31%–56%) while it changes about 6%–27% at the vortex boundary. In the merging process of two adjacent vortices, the variation of fluid density in the two vortices is slight, which shows that the merging process is probably of a peer-to-peer combination of fluid inside the two adjacent vortices. Considering the practical engineering applications, the density distribution characteristics of fluid inside the vortex in the supersonic mixing layer with different inflow densities of its upper and lower layers are also investigated, and the results show that the density distribution of the fluid inside a vortex is symmetrical about the longitudinal direction (y-axis), but not the flow direction (x-axis). It is also found that the density distribution near the vortex boundary is determined by the inflow density there, so a good strategy of reducing the aero-optical effects caused by the supersonic mixing layer is that the difference in density between the upper and lower layers should be as small as possible.
Physics and topological properties of periodic and aperiodic transmission line networks
Authors: Jiang Tian-Shu , Xiao Meng , Zhang Zhao-Qing , Chan Che-Ting ,   Physics Department, Hong Kong University of Science and Technology, Hong Kong, China,   School of Physics and Technology, Wuhan University, Wuhan 430072, China
Published: December 2020

Transmission line is a common kind of one-dimensional waveguide. In addition to being widely used in engineering, the transmission lines can be used in proof-of-principle experiments in basic scientific research. For example, the wave equations governing the transmission line and quantum wire are equivalent, so transmission lines are widely used in the research of quantum graphs. The transmission line network equations are similar to the equations of zero-energy tight binding model, so the transmission line network can also be used to study some physical properties predicted by the theories based on tight binding model, and examples include Anderson localization, band dispersions, topological properties, etc. According to the transmission line network equations, we review some applications of transmission lines in the research fields mentioned above. We will discuss Anderson localization in one-, two-, and three-dimensional networks, the band structures of periodic and quasiperiodic networks, and the angular moment-dependent topological transport in transmission line network. We introduce the methods and results in detail to show the potential of transmission lines in basic scientific research.
Cherenkov radiation based on metamaterials
Authors: Lin Yue-Chai , Liu Fang , Huang Yi-Dong ,   Department of Electronic Engineering, Beijing National Research Center for Information Science and Technology, Tsinghua University, Beijing 100084, China
Published: December 2020

Cherenkov radiation (CR) is an electromagnetic radiation emitted by charged particles traveling through a dielectric medium at a speed faster than the phase velocity of light. CR plays an important role in the fields of particle detection, biomedicine and electromagnetic-radiation source. Recently, metamaterials demonstrate their novel mechanical, acoustic, and optical properties by delicately designing the structures and materials. In metamaterials, the electromagnetic properties, such as wave propagation, coupling, and radiation, could be flexibly manipulated. Thus, it is expected that the combination of vacuum electronics and micro- & nano-photonics would result in numerous novel phenomena and effects by having free electrons interacting with metamaterials. In this paper, we firstly review the concept and generation mechanism of CR. Then, recent research advances in the CR generation by using different types of metamaterials are reviewed, including threshold-less CR in hyperbolic metamaterials, reverse CR in negative metamaterials, CR lasing based on high Q-factor metamaterials and Smith-Purcell radiation manipulation with metasurfaces. The unique characteristics and interesting mechanisms of CR based on these metamaterials are elaborated. The research and development of interaction between free electrons and various metamaterials open up possibilities for realizing novel integrated free-electron devices.
Experimental study on neutron single event effects of commercial SRAMs based on CSNS
Authors: Wang Xun , Zhang Feng-Qi , Chen Wei , Guo Xiao-Qiang , Ding Li-Li , Luo Yin-Hong ,   State Key Laboratory of Intense Pulsed Radiation Simulation and Effect, Northwest Institute of Nuclear Technology, Xi’an 710024, China
Published: December 2020

The experiment of neutron single event effect was carried out at China Spallation Neutron Source (CSNS) back-n on 13 kinds of commercial SRAM. The single event upset (SEU) cross section of each device was obtained, and multiple cell upsets (MCU) were extracted from the SEUs using a statistical method without layout information. The influences of the test pattern, feature size and device layout on the SEU cross section and MCU were studied. The results show that the test pattern has little influence on the SEU cross section of the devices, but has a great influence on the MCU ratio of some devices. The feature size has influence both on the SEU cross section and the MCU ratio of the devices. The influence on SEU cross section is not definite. The influence on the MCU ratio is definite. Both the ratio and the maximum size of the MCUs increase with the decrease of the feature size. The difference of layout has great influence both on the SEU cross section and the MCU ratio of the device. In addition, compared with the results of plateau irradiation, the ratio of MCU in CSNS back-n is less than that of plateau irradiation. There are two reasons for this difference. One is that the energy spectrum of CSNS back-n is softer than that of the atmospheric neutron. The other is the neutron beam at CSNS back-n is perpendicular to the device under test. Therefore, evaluating the atmospheric neutron SEE using CSNS back-n line may underestimate the MCU ratio of the device under test. The experimental data, analytical methods and results obtained in this paper are valuable for the researchers to carry out the atmospheric neutron SEE test and the evaluation of devices on atmospheric neutron SEE.
Liquid phase epitaxial layer by layer dipping assembly of metal-organic framework thin films and their physical property
Authors: Wang Da-Wei , Gu Zhi-Gang , Zhang Jian ,   State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou 350002, China
Published: December 2020

Metal-organic framework (MOF) is a new kind of inorganic-organic hybrid porous ordered crystal material, which is connected by metal nodes and organic ligands through coordination bond. Because of its large specific surface area, high stability, diverse structure and adjustable function, MOF has received wide attention. The improvements in preparation and functionalization of MOF thin films expand their application fields. In this paper, the method for assembly of surface coordinated metal-organic framework thin films (SURMOF) by liquid phase expitaxial layer-by-layer dipping method is introduced, and the physical properties of some SURMOFs in optics, electricity and other aspects are summarized, and the application prospect of SURMOF is prospected as well.
A new method for identifying TE01δ mode during microwave dielectric measurements of low-loss materials
Authors: Li Lei , Yan Han , Chen Xiang-Ming ,   School of Materials Science and Engineering, Zhejiang University, Hangzhou 310027, China
Published: December 2020

The metal resonant cavity method working with TE01δ mode is a universal method for evaluating the microwave dielectric properties of low-loss materials. All the microwave dielectric resonators are multi-mode resonators, so the correct identification of TE01δ mode is the basis for the microwave dielectric measurements. The TE01δ mode can be identified by predicting the resonant frequency and its variation with resonator size, expelling the spurious modes according to the exciting conditions, etc., while these methods are relatively complex and sometimes unreliable. In the present work, a simple method for accurately identifying the TE01δ mode is developed. A low-loss reference sample with known dielectric properties is introduced and placed in the cavity for the first step, and the to-be-measured sample is placed on the reference sample for the second step. The rough permittivity of the to-be-measured sample can be calculated from the TE01δ-mode resonant frequencies in the two steps through the finite element analysis, and is used to predict the resonant frequency for TE01δ mode when only the to-be-measured sample is placed in the cavity. The difference between the predicted and measured TE01δ-mode resonant frequencies for the to-be-measured sample is less than 1%, so that the TE01δ mode can be easily distinguished from the spurious modes and accurately identified.
Advances in spatial analog optical computing devices
Authors: Zhou Yi , Chen Rui , Chen Wen-Jie , Ma Yun-Gui ,   State Key Laboratory of Modern Optical Instrumentation, International Research Center for Advanced Photonics, College of Optical Science and Engineering, Zhejiang University, Hangzhou 310058, China
Published: December 2020

Spatial analog optical computing devices possess the capability of high-throughput, real-time and low-energy information processing. Optical metamaterials, which are ultracompact in structure and possess powerful ability to control the light, can be utilized to establish miniatured and integrated spatial analog optical computing devices. The methods of designing the spatial analog optical computing devices could be mainly classified as two kinds—4F system method and Green’s function method. The 4F system method requires two Fourier transform lenses and a spatial frequency filter, where the actual computing procedure is performed in the spatial domain. The 4F system is usually bulky and complicated. The Green’s function method directly leverages the nonlocal response of the carefully tailored optical materials to implement analog computing procedure in the spatial frequency domain and its structure is compact without extra Fourier transform components. Research advances in spatial analog optical computing devices by using these two methods for the last few years are introduced in this paper. These researches could be classified as differentiators, integrators, equation solvers and spatial frequency filters according to the standard of computing functions. The approaches to designing these devices are further demonstrated. Then, computing devices which could realize spatial analog first-order difference by use of the spin-orbit interaction proposed recently are introduced. Finally, application fields and study prospects of spatial analog optical computing devices are discussed and summarized.
Numerical prediction of structural stability and thermodynamic properties for MgF2 with fluorite- type structure under high pressure
Authors: Sun Xiao-Wei , Song Ting , Liu Zi-Jiang , Wan Gui-Xin , Zhang Lei , Chang Wen-Li ,   School of Mathematics and Physics, Lanzhou Jiaotong University, Lanzhou 730070, China,   Department of Physics, Lanzhou City University, Lanzhou 730070, China
Published: December 2020

MgF2 is an important member of alkaline-earth fluorides and has a wide range of applications in industry. Meanwhile, MgF2 occurs naturally as a mineral sellaite. Compared with the study of its electronic structure and optical properties, the researches of the behavior under high pressure of MgF2, especially the thermodynamic properties are still limited. The high-pressure melting, volume thermal expansion coefficient, and thermoelastic parameter of the Earth’s lower mantle mineral, like MgF2, are of interest and importance for understanding the physical nature of the functional material and for recognizing the structural compositions, dynamics, evolution and origin of the earth. Using the first-principles calculations based on density functional theory, the thermodynamic, mechanical, and dynamic stability of the fluorite-type structure for MgF2 are systematically studied. The calculations indicate that the fluorite-type structure is a high-pressure phase and it is stable at least up to 135 GPa. According to the principle of equal enthalpies, the phase transition pressure of MgF2 crystal from stable rutile structure to high pressure fluorite structure is determined to be 19.26 GPa and 18.15 GPa based on the the generalized gradient approximation and local density approximation calculations, respectively. The high-temperature structural stability of MgF2 with the fluorite-type structure is investigated and confirmed by using the classical molecular dynamics (MD) simulations by taking into account the molar volume and total energy change behavior in a temperature range from 300 to 6000 K. On the basis of previous research, the volume thermal expansion coefficient, isothermal bulk modulus, and thermoelastic parameter of MgF2 with the CaF2-type fluorite structure are predicted systematically in a temperature range from 300 to 1500 K and in a pressure range from 0 to 135 GPa with the help of the generalized gradient approximation of the revised Perdew-Burke-Ernzerhof form combined with quasiharmonic Debye model calculations and the molecular dynamics method combined with reliable interatomic potentials. An important discovery is that the thermoelastic parameter of this material under low temperature and low pressure is not a constant as assumed usually in previous studies of the equation of states, but it approaches to a constant under both high temperature and high pressure.