bluuebunny/crossref_metadata_2025 huggingface dataset:
Attitude estimation and three-axis magnetometer on-line calibration based on moving horizon estimation
Authors: Zhao Guo-Rong  , Huang Jing-Li  , Su Yan-Qin  , Sun Cong  ,   Department of Control Engineering, Naval Aeronautical and Astronautical University, Yantai 264001, China;,   Naval Unit 91980, Yantai 264001, China
Published: December 2020

According to the attitude estimation and three-axis magnetometer on-line calibration, a real time moving horizon estimation algorithm is presented in this paper. First, moving horizon estimation filter is designed since system constraints existing in most practical cases cannot be solved analytically in the framework of Kalman filter. Taking advantage of the optimal problem in dealing with constraints, the presented method converts the attitude estimation problem into an optimal one by which the quaternion normalization property can be solved analytically in smaller searching space with better efficiency and accuracy. Second, through a series of linearization of system equations, Gauss-Newton iterative method is applied in the horizon window composed of finite history information to obtain the best state estimation and meet the real time requirement at the same time. Once the newest best state estimation value is obtained, it will be sacked into the horizon window and the oldest one discarded. By this way, the filter is moving forward. Finally, based on the proposed method, the three-axis magnetometer parameter on-line calibration combined with attitude estimation is solved without adding any system state dimension, which can also make sure that the measurements with three-axis magnetometer are in the form of vector as its obvious benefits in the sense of ensuring information quantity. On considering the extreme environment such as great temperature gradient, mechanical pressure and complex electromagnetic fields, different from that of the off-line calibration, the calibration parameter is changed definitely. So the on-line calibration is necessary though neglected by most papers. Simulation results show that under the condition of small initial errors, the difference of accuracy among EKF, UKF and moving horizon estimation is small. But the computational burden of the last one is relatively large. The advantage of the described method is not so obvious in this case. But when the initial errors are large, the moving horizon estimation still can get the precise results no matter how great are the EKF (extended Kalman filter) and UKF (unscented Kalman filter) deviated from the true values. Thus the proposed method has its high accuracy and poor sensitivity of the initial and systematic errors along with fast convergence, all of which are vital in most actual environments.
Pulse response of a monostable system
Authors: Leng Yong-Gang  , Zhao Yue  ,   School of Mechanical Engineering, Tianjin University, Tianjin 300072, China;,   Key Laboratory of Mechanism Theory and Equipment Design of Ministry of Education, Tianjin University, Tianjin 300072, China
Published: December 2020

The potential function of a mono-stable system is studied in this paper. The response of pulse series with different half-peak width via the mono-stable system is analysed. Our conclusion is that the larger the half-peak width of the input pulse series, the higher the height of the output pulse series . Distortion of the pulse response wave appears. This is the reason that the potential function of the mono-stable system is similar to the horizontal line around zero point.#br#In view of the difficulties of adjusting parameter of the mono-stable system to reach stochastic resonance, a method of moving pulse series is put forward. Adjusting the system parameter is not considered but the stochastic resonance of the pulse signal is realized by setting an offset in the method. To reduce the response pulse wave distortion, a mechanism for the proposed method to reduce the distortion is discussed in detail. When noise exists, the mechanism reveals that the moving pulse series method can adjust the distribution of the noise power spectrum and improve the mono-stable stochastic resonance. Therefore, the method proposed in this paper is helpful to detect pulse signal masked by noise.
Study on dynamical characteristics of a meminductor model and its meminductor-based oscillator
Authors: Yuan Fang  , Wang Guang-Yi  , Jin Pei-Pei  ,   Key Laboratory of RF Circuits and Systems, Ministry of Education of China; Institute of Modern Circuits and Intelligent Information, Hangzhou Dianzi University, Hangzhou 310018, China
Published: December 2020

A meminductor is a new type of nonlinear inductor with memory, which is generalized from the concept of a memristor and defined by current-flux. This paper presents a flux-controlled meminductor model with a smooth quadratic function and designs its corresponding equivalent circuit, which can be used as an emulator to imitate the behavior of a meminductor when actual solid-state meminductor has not yet appeared. Furthermore, a new chaotic oscillator is designed based on this meminductor model, and the dynamical behaviors of the oscillator are investigated, such as chaotic attractors, equilibrium points, Lyapunov exponent spectrum, bifurcations and dynamical map of the system, etc. Bifurcation analysis shows that the meminductor can make the oscillator produce periodic and chaotic oscillations. Moreover, an analog circuit is designed to confirm the correction of the proposed oscillator using the proposed equivalent circuit model of meminductor. It is shown that the experimental results are in good agreement with that of the numerical simulations and the theoretical analysis.
Improved averaged model and stability analysis of voltage-mode controlled positive output super-lift Luo converter
Authors: Wang Fa-Qiang  , Li Jing  , Ma Xi-Kui  ,   State Key Laboratory of Electrical Insulation and Power Equipment, School of Electrical Engineering, Xi'an Jiaotong University, Xi'an 710049, China;,   Xi'an Institute of Space Radio Technology, Xi'an 710100, China
Published: December 2020

Positive output super-lift (POSL) Luo converter, which has some particular good features: such as its power switch being grounded, high voltage gain and positive polarity output, is a good topology for overcoming the drawbacks of the conventional Buck and Boost converters to obtain high output voltage and power for satisfying the requirements in practical engineering. In this paper, based on the averaging method and taking into account the abrupt changing of the voltage across the energy-transferring capacitor, the improved reduced order averaged model and the corresponding small signal model of the POSL Luo converter are established, and its transfer function from the duty cycle to the output voltage is derived and analyzed. By combining the derived transfer function from the duty cycle to the output voltage of the POSL Luo converter, with that for the voltage compensator and that for the pulse width modalation (PWM) generator, the transfer function from the reference voltage to the output voltage of the voltage-mode controlled POSL Luo converter is also derived. And then, the stability of the voltage-mode controlled POSL Luo converter is identified by calculating the poles of its transfer function from the reference voltage to the output voltage, so the corresponding stability boundaries are obtained. The power electronic simulator (PSIM) software is applied to simulate the POSL Luo converter in time domain and frequency domain to preliminarily confirm the effectiveness of the established transfer function from the duty cycle to the output voltage of the POSL Luo converter, and to simulate the voltage-mode controlled POSL Luo converter to preliminarily verify the theoretical analysis about its stability. Finally, the hardware circuits for the POSL Luo converter and the voltage-mode controlled POSL Luo converter are designed, and the circuit experimental results in time domain from the digital oscilloscope and in frequency domain from the impedance/gain-phase analyzer are presented for further validation. Theoretical analysis, PSIM simulations and circuit experiments are in basic agreement with one other, and all of them demonstrate that it is effective to use the improved average model to analyze the performance of the POSL Luo converter and the stability of the voltage-mode controlled POSL Luo converter.
Chaos synchronization of coronary artery system based on higher order sliding mode adaptive control
Authors: Zhao Zhan-Shan  , Zhang Jing  , Ding Gang  , Zhang Da-Kun  ,   School of Computer Science and Software Engineering, Tianjin Polytechnic University, Tianjin 300387, China;,   School of Textiles, Tianjin Polytechnic University, Tianjin 300387, China;,   Equipment management department, Tianjin Vocational Institute, Tianjin 300410, China;,   Department of the Management and Construction of Teaching Resources, Tianjin Radio & TV University, Tianjin 300191, China
Published: December 2020

Many biomedical engineering fields are studied by combining with nonlinear science which has major advances in theoretical curing related diseases. The coronary artery system is chosen as a muscular blood vessel model. With the change of vessel diameter, some chaotic behaviors will occur which may cause complex diseases such as myocardial infarction.#br#In order to avoid the undesired chaotic motion, this paper investigates the finite-time chaos synchronization problem for a coronary artery system by utilizting high-order sliding mode adaptive control method. First, the error chaos synchronization system is obtained using the master and slave systems. Second, the error chaos synchronization system can be transformed into an integrator chain system by coordinate transformation, which is equivalent to an error chaos synchronization system. Considering that the sliding mode control has main obstacle (the control high activity and chattering phenomenon), a high-order sliding mode adaptive controller is designed for a coronary artery system with unknown disturbances at geometric homogeneity and integral sliding mode surface. The proposed method shows that the drive and response systems are synchronized and the states of the response system track the states of the drive system in finite-time. This approach does not require any information about the bound of disturbances in advance. Theoretic analysis based on Lyapunov theory proves that the systems with the proposed controller could be stabilized in finite-time. The convergence time of the system states is estimated. In order to alleviate the chattering effect, we use tanh(·) function in place of sign(·) function to design an improved high-order sliding mode adaptive controller. Simulation results show that the proposed adaptive sliding mode controller can achieve better robustness and adaptation against disturbances, which offer the theoretic basis for curing myocardial infarction.
Micro-damage characteristics of incipient spall in high-purity copper
Authors: Peng Hui  , Pei Xiao-Yang  , Li Ping  , He Hong-Liang  , Bai Jin-Song  ,   Key Laboratory of Shock Wave and Detonation Physics, Institute of Fluid Physics, China Academy of Engineering Physics, Mianyang 621900, China;,   State Key Laboratory of Explosion and Technology, Beijing Institute of Technology, Beijing 100081, China
Published: December 2020

Dynamic damage of material is a complex process that is dependent on lots of effects on a mesoscale, including grain size, morphology and micro-voids. In order to study the shocked lead micro-damage characteristics in oxygen-free high-purity copper, the variational thickness values of flyers and samples are designed to vary pulse duration and strain rate in plate-impact experiment, and the special recovery chamber and surface profile measurement system are used for soft-recovery and cross-section measure respectively. Based on the reconstruction, quantitative and statistical analysis, it is found that the longer pulse duration and higher shock loading stress bring about more serious local damage in oxygen-free high-purity copper. The mensurable damage width of sample cross-section results from the damage evolution on a sub-micron scale. Critical evolution time of sub-micron is observed to decrease with strain rate increasing, suggesting that damage evolution speed of sub-micron becomes faster as strain rate increases. The void size distribution of recovered sample is presented, and the topological characteristic transition accompanied with nucleation, growth, and coalescence processes of microscopic voids is also discussed. Through a comparison of difference between this work and the literature of previous research, a physical explanation of voids size distribution characteristics of oxygen-free high-purity copper is presented.
Electron correlations and orbital selectivities in multiorbital models for iron-based superconductors
Authors: Yu Rong  ,   Beijing Key Laboratory of Opto-electronic Functional Materials & Micro-nano Devices, Department of Physics, Renmin University of China, Beijing 100872, China
Published: December 2020

We review the recent theoretical progress of the multiorbital effects on the electron correlations in iron-based superconductors. Studying the metal-to-insulator transitions of the multiorbital Hubbard models for parent compounds of iron-based superconductors, a Mott transition is generally realized. The natures of both the Mott insulating and the metallic phases are affected by the Hund's rule coupling. In alkaline iron selenides, Hund's rule coupling stabilizes a novel orbital-selective Mott phase, in which the iron 3d xy orbital is Mott localized, while other 3d orbitals are still itinerant. We discuss the effects of the orbital selectivity on normal state properties and the superconductivity of the iron-based systems.
Heavy-fermion superconductivity and competing orders
Authors: Yang Yi-Feng  , Li Yu  ,   Institute of Physics, Chinese Academy of Science, Beijing 100190, China;,   Collaborative Innovation Center of Quantum Matter, Beijing 100190, China
Published: December 2020

One of the most salient features of heavy fermion superconductivity is its coexistence with various competing orders. Superconductivity often emerges near or at the border of these exotic orders and their interplay may give rise to many interesting quantum phenomena. In this paper, we give a brief review of the various heavy fermion superconductors discovered so far and show there may exist an intimate connection between their superconducting pairing and quantum critical spin/charge/orbital fluctuations. We classify these superconductors into three categories:(A) CeM2X2, CenMmIn3n+2m, CePt3Si, CeMX3, CeNiGe3, Ce2Ni3Ge5 and CePd5Al2, in which superconductivity emerges at the border of antiferromagnetic phase; YbRh2Si2, in which superconductivity was very recently found inside the antiferromagnetic phase at 2 mK; UX2Al3 and UPt3, in which superconductivity occurs inside the antiferromagnetic phase; and UBe13 and U6Fe, in which the connection between magnetism and superconductivity is not yet clear. Among them, CePt3Si and CeMX3 are noncentrosymmetric, while UPt3 exhibits spin triplet pairing inside an antiferromagnetic phase.(B) UGe2, URhGe, UCoGe, UIr and U2PtC2, are spin triplet superconductors under the influence of ferromagnetic order or fluctuations.(C) URu2Si2, PrOs4Sb12, PrT2X20, Pu-115, NpPd5Al2 and -YbAlB4, in which superconductivity may be related to other exotic quantum states or fluctuations such as hidden order, valence fluctuations and quadrupolar fluctuations.In these compounds, f-electrons may participate in both superconductivity and other competing orders and often behave simultaneously itinerant and localized. These could be described by a phenomenological two-fluid theory, in which two coexisting fluidsan itinerant heavy electron fluid (the Kondo liquid) and a spin liquid of unhybridized local f-momentscompete to give rise to the various low temperature orders as well as superconductivity. Combining the two-fluid picture and the idea of spin-fluctuation-induced superconducting pairing, a BCS-like formula is proposed for calculating the superconducting transition temperature, and the results are found to be in good agreement with the experimental data for Ce-115. This model can explain naturally the microscopic coexistence of superconductivity and antiferromagnetism in these materials, and provides a promising guidance to other heavy fermion superconductors to achieve a systematic examination of the interplay between superconductivity and other exotic orders.
First-principle study of electronic structure and optical properties of Ba(Mg1/3Nb2/3)O3
Authors: Shen Jie  , Wei Bin  , Zhou Jing  , Shen Shirley Zhiqi  , Xue Guang-Jie  , Liu Han-Xing  , Chen Wen  ,   State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Wuhan 430070, China;,   School of Materials Science and Engineering, Wuhan University of Technology, Wuhan 430070, China;,   CSIRO Materials Science and Engineering, Highett, VIC 3190, Australia
Published: December 2020

Transparent ceramics have been widely researched for their broad range of applications, e.g. from optical windows to laser and optoelectronic switches. However, the challenge is to obtain the optical materials with high refractive index to miniaturize optical functional elements, such as lens for optical information storage and waveguides for flat optical components. The hexagonal complex perovskite Ba(Mg1/3Nb2/3)O3(BMN) ceramic, being widely researched as a type of microwave dielectric ceramics, presents the excellent dielectric properties such as high dielectric constant and high Q value, which indicate its potential application as optical materials. In this paper, the electronic structure of BMN is calculated by using the first principle method, to analyze and predict its intrinsic optical properties. The hexagonal complex perovskite BMN ceramic is synthesized using conventional solid-state reaction at 1600 ℃ for 24 h. The structure parameters are obtained through Rietveld refinement of X-ray diffraction data. The crystal model is established, based on the Rietveld refinement result of the XRD test on synthesized BMN (with the weighted profile R-factor Rwp=6.73%, the profile R-factor Rp=5.05%), and then the crystal geometry optimized. With the optimized crystal model, the energy band structure, density of states and optical properties of BMN are calculated using the first principle method based on density functional theory (DFT) with local density approximation (LDA). Results show that BMN has an indirect band gap of 2.728 eV. There are the strong ionic interactions between Mg and O as well as Ba and O, while there is covalent interaction between Nb and O. The energy band near the Fermi level is mainly occupied by O-2p and Nb-4d electrons, which forms the d-p hybrid orbits. With real band gap correction, the optical properties of BMN are obtained from the definition of direct transition probability and the Kramers-Kronig dispersion relations along the polarization directions [100] and [001], including the complex dielectric function, absorption coefficients and reflectivity, respectively. It is shown that the optical properties of BMN are nearly isotropic. According to the Lambert-Beer's law, the intrinsic transmittance of BMN ranges from 77% to 83% in the visible region, and its refractive index is dispersive, ranging from 1.91 to 2.14. Experimental test results are consistent with the theoretical calculation results.
High temperature thermoelectric performance of Ca2+ doped CdO ceramics
Authors: Liu Ran  , Gao Lin-Jie  , Li Long-Jiang  , Zhai Sheng-Jun  , Wang Jiang-Long  , Fu Guang-Sheng  , Wang Shu-Fang  ,   Hebei Key Laboratory of Optoelectronic Information Materials, the College of Physical Science and Technology, Hebei University, Baoding 071002, China
Published: December 2020

Oxide thermoelectric materials have been considered to be potential candidates in high-temperature thermoelectric power generation, however, their high thermal conductivity renders them inferior to the conventional thermoelectric materials and limit their practical application. In this paper, we successfully reduce the thermal conductivity of CdO polycrystals through Ca2+ doping, and the improvement in ZT is also obtained due to the low thermal conductivity. Cd1-xCaxO (x=0, 0.01, 0.03, 0.08) polycrystals are synthesized by adding CaCO3 into CdO via conventional solid-state reaction method and their high-temperature thermoelectric properties are studied. XRD results reveal that all samples are composed of CdO polycrystals, and the lattice parameters increase with Ca2+ content due to the larger radius of Ca2+ as compared with that of Cd2+. Addition of CaCO3 can induce the formation of point defects as well as pores in the CdO polycrystals, thus inhibits the grain growth of CdO and induces the increase of grain boundaries. The main electron carriers in CdO are reported to be shallow level donor impurities formed by oxygen vacancies; as the Ca2+ concentration in Cd1-xCaxO increases, the conduction band minimum of the samples shifts upward and the level of donor impurity becomes deeper, finally resulting in the decrease of electron carrier concentration. Meanwhile, the reduced carrier concentration in the doped samples leads to the increase of both the electrical resistivity ρ and the absolute Seebeck coefficient |S|, while the electrical thermal conductivity κ e will decrease with increasing Ca content. Investigations on the thermal properties of the obtained samples demonstrate that the introduction of Ca2+ is effective to suppress the thermal conductivity. The increment of pores and grain boundaries in the doped samples will enhance the long-wavelength phonon scattering, resulting in the decrease of phonon thermal conductivity κ p. Furthermore, the point defects, which come from the mass and size differences between Ca and Cd atoms, also act as scattering centers and lead to a considerable decrease in phonon thermal conductivity. Due to the simultaneous reduction of both electrical and phonon thermal conductivity, the total thermal conductivity κ may substantially be suppressed, for example, the total thermal conductivity of Cd0.95Ca0.05O reaches 2.2 W·m-1·K-1 at 1000 K, a remarkable decrease as compared with pristine CdO, which is 3.6 W·m-1·K-1 measured at the same temperature. Benefiting from the drastically reduced thermal conductivity, Cd0.99Ca0.01O polycrystals can achieve a high ZT of 0.42 at 1000 K, 27% higher than the pure CdO, which is one of the best n-type oxide TE materials reported so far.
Curvature weight method of solving the point reactor neutron kinetic equations
Authors: Li Ming-Rui  , Li Hao-Feng  , Chen Wen-Zhen  , Hao Jian-Li  ,   Department of Nuclear Energy Science and Engineering, Naval University of Engineering, Wuhan 430033, China;,   Naval Nuclear Safety Department, Beijing 100841, China
Published: December 2020

The point kinetic equations are the system of a couple stiff ordinary differential equations. Many studies have focused on the development of more advanced and efficient methods of solving the equations, such as the high order Taylor polynomials method, the Haar wavelet operational method, the fractional point-neutron kinetic model method, the basis function method, the homotopy analysis method, and other methods. Most of these methods are successful in some specific problems, but still have, more or less, disadvantages. For example, the accuracy of the Haar wavelet operational method is limited by the collocation points, and it needs more computing time for a high precision. Aiming at the requirements that some numerical calculation results must have the higher precision and only the positive error in the nuclear reactor safety engineering and ship reactor for the maneuverability, in this paper we try to look for a new numerical method to satisfy that the calculation value is slightly higher than the real value when the actual curve is upward convex or downward concave, and the error is not greater than that by the Euler and improved Euler method. The new method is so-called the curvature weight (CW) method, which is based on the curvature circle method and considers the contributions of two curvatures at the interval step point to the average curvature inside the interval step. Using the decoupling method to remove the stiffness of equations and the instantaneous jump approximation to derive the neutron differential equations, the first and second derivative of neutron density are obtained. Then the CW method is used to solve the point reactor neutron kinetic equations, and thus obtaining the numerical solution. Compared with the results by the Euler and improved Euler method, the numerical calculation results by the CW method are always higher than the real value, and the calculation accuracy and speed are improved significantly. When this new method is used to solve the point reactor neutron differential equations with the step and linear reactivity inserted into the subcritical reactor, the numerical results which satisfy the requirements of positive calculation error and high precision can be obtained quickly. After improving the calculation step length, the precision reduction by the CW method is significantly lower than that by the Euler and improved Euler method. So the CW method can greatly shorten the total computing time, and it is also effective for most of differential equation systems.
Effects of initial states on the quantum correlation in Bose-Hubbard model
Authors: Guo Hong  ,   College of Physical Science And Technology, Central China Normal University, Wuhan 430079, China
Published: December 2020

Quantum correlation is an important resource in quantum information, quantum computation, and quantum metrology. Quantum entanglement, Einstein-Podolsky-Rosen (EPR) quantum steering and Bell nonlocality are the major quantum correlations. For quantum entanglement and Bell nonlocality, two subsystems play the same significant roles. EPR quantum steering is stronger than entanglement and weaker than Bell nonlocality. It represents the ability of one subsystem to nonlocally affect another subsystem's states through local measurements. In this paper, the dynamic quantum correlation between the modes in the two-site Bose-Hubbard model is investigated. According to Hillery-Zubairy entanglement criterion and based on maximum mean quantum Fisher information, the influences of initial states on the quantum entanglement evolutions are explored. If the coupling between the modes is much greater than that of the particles at the same site, and the initial states are symmetric or anti-symmetric SU(2) coherent states, the quantum correlations show simple periodic evolutions. The oscillation amplitudes of the evolutions increase with the interaction between the particles at the same site. The oscillation period decreases with the coupling strength between the modes. The dependence of the period on the interaction of the particles at the same site is related to the initial states. In other words, the time evolutions of quantum correlation are closely related to the symmetry of the initial states. In the case of symmetric (anti-symmetric) SU(2) coherent state and repulsive (attractive) interaction of the particles at the same site, the system presents two-way quantum steering. When the subsystem exchange symmetry of the initial states is broken, the collapse and revival of quantum correlation appear, moreover one-way quantum steering emerges in the infancy. One-way quantum steering is asymmetric for two subsystems. So exchange asymmetry of the initial state is necessary condition of one-way quantum steering when the Hamiltonian of the system is symmetric for two subsystems.
Nanometer resolution coherent anti-Stokes Raman scattering microscopic imaging
Authors: Zhang Sai-Wen  , Chen Dan-Ni  , Liu Shuang-Long  , Liu Wei  , Niu Han-Ben  ,   Key Laboratory of Optoelectronics Devices and Systems of Ministry of Education and Guangdong Province, College of Opto-Electronics Engineering, Shenzhen Key Laboratory of Biomedicine Engineering, Shenzhen University, Shenzhen 518060, China
Published: December 2020

Coherent anti-Stokes Raman scattering (CARS) microscopy can break through the optical diffraction limit by applying the additional probe beam induced phonon depletion (APIPD). Using this method, we can obtain a spatial resolution beyond the optical diffraction limit by introducing a doughnut additional probe beam to deplete phonons at the periphery of the focal spot. To achieve higher spatial resolution and better phase matching conditions, it is necessary to use high numerical aperture objectives, whereas scalar diffraction theory is no longer valid. According to the full vector diffraction theory, we calculate the intensity distributions at the focal plane when the linearly and circularly polarized lights pass through a spiral phase plate and an objective with high numerical aperture successively. The result shows that the circular polarization can generate the perfectly doughnut-shaped focal spot, which is more suitable for the additional beam than the linear polarization induced beam. Furthermore, we analyze the APIPD induced CARS process with the full quantum theory. Simulations indicate that a spatial resolution as high as 45 nm could be realized when the ratio between the intensities of additional probe and probe is 80. And the spatial resolution turns higher with increasing the power of additional probe.
Comparison of polarization property of partially coherent beam between propagating along an uplink path and a downlink path in atmospheric turbulence
Authors: Ke Xi-Zheng  , Wang Jiao  ,   School of Automation and Information Engineering, Xi'an University of Technology, Xi'an 710048, China
Published: December 2020

In this article, we take partially coherent electromagnetic Gaussian-Schell model (EGSM) beam as a research object. Based on the unified theory of coherence and polarization and the generalized Stokes parameters of random electromagnetic beams, the expressions of degree of polarization (DoP) and orientation angle of EGSM beam that propagates in the slant atmospheric turbulence, are derived. And the expressions are used to investigate the difference in polarization property of EGSM beam between propagating along an uplink path and a downlink path in the atmospheric turbulence. The results show that under the same conditions, the DoP distribution of EGSM beam propagating along a downlink path is more concentrated than that along an uplink path. When EGSM beam propagates along a downlink path, the maximum DoP corresponding to the propagation distance is larger than along an uplink. Therefore, when EGSM beam propagates along a downlink path, the detector can receive beam information at the longer distances.
Influence of aspect ratio on the light scattering properties of spherical aerosol particles
Authors: Zhang Xue-Hai  , Wei He-Li  , Dai Cong-Ming  , Cao Ya-Nan  , Li Xue-Bin  ,   Key Laboratory of Atmospheric Composition and Optical Radiation, Anhui Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Hefei 220031, China;,   Graduate University of Chinese Academy of Sciences, Beijing 100039, China;,   School of Environmental Sciences and Optoelectronic Technology, University of Science and Technology of China, Hefei 230031, China
Published: December 2020

The influence of aspect ratio on the light scattering properties of ellipsoidal particles is studied by using T-matrix method and discrete ordinate method in this paper. The light scattering characteristic quantities including extinction efficiency, asymmetrical parameter, single scattering albedo, scattering phase matrix, and bidirectional reflectance distribution function (BRDF) are computed. It is found that light scattering properties of ellipsoidal particles are sensitive to aspect ratio. The aspect ratio can influence the oscillation frequencies and amplitudes of the scattering parameters except some special size parameters. The value of asymmetrical factor could be as large as 0.3 in wave crest value of size parameter while it is no more than 0.1 at the balance location. As for the multiple scattering, the characteristics of BRDF for different aspect ratios in different incident angles and optical thickness values are analyzed, and for a further study, the relative differences of BRDF influenced by aspect ratio, optical thickness, and incident angle are analyzed. The results show that the variation trends of BRDF for the ellipsoidal particles with various aspect ratios are basically the same. However, the curve of BRDF of spherical particles (i.e., with their aspect ratios being 1) is more variable. With the increasing of aerosol optical thickness and aspect ratio, the curves of BRDF at different aspect ratios for ellipsoidal particles tend to a steady and similar value and the relative difference of BRDF decreases. But with the increasing of aerosol optical depth, the relative difference of BRDF increases with the increasing of incident angles, especially in large optical thickness, the value of the relative difference of BRDF can be as large as 15%.
Quantum imaging of cooperative target based on photon-counting regime
Authors: Li Ming-Fei  , Yang Ran  , Huo Juan  , Zhao Lian-Jie  , Yang Wen-Liang  , Wang Jun  , Zhang An-Ning  ,   Quantum Engineering Research Center, Beijing Institute of Aerospace Control Devices, China Aerospace Science and Technology Corporation, Beijing 100094, China
Published: December 2020

Quantum imaging is such an technique that the total light intensity transmitted through or reflected by an object is collected by a bucket detector, which generally is a photodiode with a collection lens in front and with no spatial resolution, and an image of the object can be retrieved through the assistance of another spatially correlated reference beam which does not interact with the object. In this paper, Quantum imaging scheme is investigated, instead of using the conventional linear detector, and a single photon detector working in a photon-counting mode is used as a bucket detector, which is the most sensitive detector in the present. It is experimentally demonstrated that quantum imaging illuminating by pseudo-thermal light can be retrieved through using the single-photon detector working in the photon-counting mode, and the averaged power received by the bucket detector is only 2 femto-Watt. It is also experimentally and theoretically demonstrated that the image of the cooperative target can be recovered through the wake scattering medium, which cannot be realized by the classical imaging method. Furthermore, it is found that the wake scattering medium has the potential application in reducing the size of the collection lens of the bucket detector, in other words, enlarging the field of view. Besides, quantum imaging recovered by correlation of intensity fluctuations and compressive sensing algorithm are compared, and the most effective ways to retrieve the image are discussed. The scheme of our experiment which is different from the traditional ways, offers a novel method to make the quantum imaging technique step further toward its applications in wake light imaging or remote sensing.
Timing synchronization based on mode-locked fiber lasers with attosecond timing jitter
Authors: Qin Peng  , Song You-Jian  , Hu Ming-Lie  , Chai Lu  , Wang Qing-Yue  ,   Key Laboratory of Opto-electronic Information Science and Technology of Ministry of Education, College of Precision Instruments and Opto-electronics Engineering, Tianjin University, Tianjin 300072, China
Published: December 2020

Mode-locked fiber lasers output ultra-short pulse trains with extremely high temporal stability, showing great potential in systems that require precise timing synchronization, such as pump-probe experiments, high-speed analog-to-digital conversion, large-scale timing distribution and coherent combination. The fiber lasers are usually simpler, less costly, more efficient and more robust to the environment than solid state lasers, making them a better option for real-world applications. With the atto second temporal resolution of the balanced optical cross-correlation (BOC) method, timing jitter of mode-locked fiber lasers has been carefully measured and optimized over the last decade. However, due to the inherently large amplified spontaneous emission noise in the long gain fiber and broad pulse width inside the laser cavity, the quantum-noise-limited timing jitter of mode-locked fiber lasers is still much higher than that of the solid state lasers. In order to further optimize the timing synchronization of mode-locked fiber laser, larger locking bandwidth is required to suppress the low-frequency timing jitter, which contributes significantly to the total amount of residual timing jitter. In this work, tight timing synchronization between two mode-locked Yb-fiber lasers is achieved via a feedback loop built on an intra-cavity electro-optic phase modulator. Both lasers work in the stretched-pulse regime, which has been proven to support the lowest quantum-noise-limited timing jitter of mode-locked fiber laser. The output of the BOC system provides a timing error discriminator of 40 mV/fs, corresponding to 13 as resolution within the integration bandwidth. When the pulse trains from both lasers are successfully synchronized, the residual timing jitter can be measured with the same signal as that used for timing synchronization Based on the residual timing jitter measurement, the intra-cavity dynamics of the laser and the locking parameters of the feedback loop can be further optimized and a tight synchronization with 400 kHz locking bandwidth is finally achieved. When performing the integration from 1 Hz to 10 MHz, the residual timing error is as low as 109 as, corresponding to 77 as averaged timing jitter of each laser. A parallel out-of-loop single-arm cross-correlation measurement is also performed to test the validity of the in-loop results, and both measurements agree with each other.
Analysis of the positional accuracy of the self-conjugate ray in a misalignment multiple-mirror optical ring cavity
Authors: Cui Li-Hong  , Yan Chang-Xiang  , Zhao Wei-Ning  , Zhang Xin-Jie  , Hu Chun-Hui  ,   Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, Changchun 130033, China;,   University of Chinese Academy of Sciences, Beijing 100049, China
Published: December 2020

In order to analyze the characteristic of the close optical axis (conjugate optical axis) and the existence condition of resonator composed of multiple reflective mirrors, the existence condition of conjugate optical axis of the multiple-resonator consisting of many flat mirrors is analyzed and derived from the angle of beam conversion coordinate transformation. The results show that a closed ray axis in resonator with odd number of mirrors can exist only if each mirror is suitably aligned, while a closed ray axis always exists in non-planar resonators with even number of mirrors, and the angle of the cavity conjugate axis direction changes due to the misalignment of different mirrors. Then from the point of view of the optical multi-pass matrix, the incidence direction of the self-conjugate ray of the resonator consisting of spherical mirrors is analyzed. A detailed analysis of conjugated axis of the resonator consisting of two flat mirrors and one spherical mirror is conducted, and the results show that when different mirrors have angle deviations, the closed conjugated optical axis remains in the cavity, the change of resonator axis occurs, and the position and orientation of new resonance surface are given, thereby indicating that in the case of resonator with spherical mirrors there is a self-conjugate ray irrespective of the other flat mirrors positions. All of these will provide theoretical guidance for achieving the high-accuracy alignment and improving the measurement accuracy of spectral measurement technology based on high-quality optical cavity.
Irradiation and temperature influence on the Bi-doped silica fiber
Authors: Liu Peng  , Liao Lei  , Chu Ying-Bo  , Wang Yi-Bo  , Hu Xiong-Wei  , Peng Jing-Gang  , Li Jin-Yan  , Dai Neng-Li  ,   Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, Wuhan 430074, China
Published: December 2020

We report Bi-doped fibers prepared by modified chemical vapor deposition combination with solution doping process. The fibers are divided into three groups under 60Co radiations with different doses. The absorption spectra and fluorescence spectra of the fiber before and after irradiation are investigated. The dependence of fluorescence intensity of the fiber on temperature (-40-70 ℃) are measured. Experimental results show that the radiation-induced absorptions (RIAs) of the fibers increase significantly at 700 nm and 800 nm with the increase of the irradiation dose. We ascribe the great enhancement of the RIA of the fiber to the generation of more Bi near-infrared (NIR) active centers. Because near infrared nonluminous valance state like Bi3+ captures free electrons and converts into Bi2+, and further into Bi+under the 60Co radiations with different doses. We also find that the NIR fluorescence spectra are stable before and after irradiation under 976 nm LD excitation. The possibility of communication in a radiation environment is proved, such as in outer space is proved. In addition, the fluorescence intensity dependence on temperature in a full-temperature range is analyzed, and we find that the fluorescence intensity decreases with the increase of temperature. It is contributed to the Bi active center that Bi+ may gradually turn into nonluminous Bi metallic colloids during thermal activation. The variation law of fluorescence intensity is analyzed in the whole range of temperature. We believe that the variation law of fluorescence intensity provides data and basis for the stable operation of bismuth-doped fiber laser in the future.
Design of two-dimensional plate directional heat transmission structure based on meta materials
Authors: Sun Liang-Kui  , Yu Zhe-Feng  , Huang Jie  ,   China Aerodynamics Research and Development Center, Mianyang 621000, China
Published: December 2020

Based on the transformation thermodynamics, the thermal conductivity expression for the unit cell of the directional heat transmission structure is derived by the oblique and rotary coordinate transformation. We obtain the two-dimensional plate directional heat transmission structure through periodically arranging the unit cells which are realized by layering copper and thermal insulation materials. The results from the numerical calculation indicate that the heat flux flows from the upper surface of the directional heat transmission structure to the two sides, while the upper and lower surface remain at low temperature. Compared with the temperature of SiO2 aerogel thermal insulation material, the upper surface temperature falls 33.3%, the low surface temperature falls 4.3%, while the temperatures of the two sides rise 40.1%. The decrease of the upper surface temperature indicates that the heat on the upper surface can be guided timely, and then the infrared radiation can be weakened. The decrease of the lower surface temperature indicates that the adiabatic efficiency of the directional heat transmission structure is superior to that of the SiO2 aerogel thermal insulation material. The heat transmission from the upper surface to the sides is conducive to the good use of the heat flux. The directional heat transmission has a potential application in the infrared stealth and heat protection.
Lateral mode suppression and experiment for the ZnO ring thin-film bulk acoustic resonator (Retracted)
Authors: Li Yu-Jin  , Yuan Xiu-Hua  , Zhao Ming  , Wang Yun-He  ,   School of Optical and Electronic Information, Huazhong University of Science and Technology, Wuhan 430074, China
Published: December 2020

In this paper, we analytically study the spurious lateral mode of the ring (circular) thin-film bulk acoustic resonator (FBAR) by using Tiersten equation. The lateral mode displacement field and frequency dispersion equation are obtained. According to the electromagnetic mode analysis, we find that the mode frequency and spurious electrical responses relate to the ratio of inner radius to outer radius (a/b) of the ring resonator, and its lateral vibration mode can be obtained by coupling other circular FBAR modes. The ring electrode can greatly reduce the number of spurious electrical responses caused by lateral resonances. Suppressing lateral mode and adjusting fundamental frequency can be achieved by controlling a/b. In this paper, the experiments for the same batch of ring and circular FBARs are carried out by using a heterodyne interferometer and a vector network analyzer, including the measurements of acoustic wave fields and eigenmode spectra, which can provide the information about vibration localization and coupling between lateral mode and thickness extensional mode. The data indicate that the lateral vibration mode of ring FBAR can be obtained by coupling the two modes of circular FBARs, whose radii are a and b, respectively, and the lateral mode pattern of n' = 0 is suppressed. When the ring resonator is designed with an a/b ratio of 0.436, the fundamental frequency (～ 1217 MHz) is the same as the (0, 1) mode frequency of the circular FBAR. Based on this observation, the acoustic wave field images and electrical spurious responses can accurately describe the lateral modes, and the obtained results accord well with the analyses of theoretical electromagnetic modes. This phenomenon may be found to have applications in the design and theoretical analysis of the resonators.