查看更多>>摘要：The dynamic range of the nuclear magnetic resonance gyroscope can be effectively improved through the closed-loop control scheme,which is crucial to its application in inertial measurement.This paper presents the analytical transfer function of Xe closed-loop system in the nuclear magnetic resonance gyroscope considering Rb-Xe coupling effect.It not only considers the dynamic characteristics of the system more comprehensively,but also adds the influence of the practical filters in the gyro signal processing system,which can obtain the accurate response characteristics of signal frequency and amplitude at the same time.The numerical results are compared with an experimentally verified simulation program,which indicate great agreement.The research results of this paper are of great significance to the practical application and development of the nuclear magnetic resonance gyroscope.
查看更多>>摘要：Improving the speed of ghost imaging is one of the main ways to leverage its advantages in sensitivity and imperfect spectral regions for practical applications.Because of the proportional relationship between image resolution and mea-surement time,when the image pixels are large,the measurement time increases,making it difficult to achieve real-time imaging.Therefore,a high-quality ghost imaging method based on undersampled natural-order Hadamard is proposed.This method uses the characteristics of the Hadamard matrix under undersampling conditions where image information can be fully obtained but overlaps,as well as deep learning to extract aliasing information from the overlapping results to obtain the true original image information.We conducted numerical simulations and experimental tests on binary and grayscale objects under undersampling conditions to demonstrate the effectiveness and scalability of this method.This method can significantly reduce the number of measurements required to obtain high-quality image information and advance application promotion.
查看更多>>摘要：Orbital angular momentum(OAM)conversion is critical in understanding interactions between a structural sound field and a planar lattice.Herein,we explore the evolution of a monochromatic acoustic vortex beam(AVB)that is scattered by a phononic crystal(PnC)or a correlated random lattice.The phenomenon is ascribed to the enhanced orbit-orbit angular momentum coupling induced by the band structure.By modifying the coupling condition,accurate and continuous micro-manipulation of AVBs can be achieved,including the transverse/lateral gravity shift,the dynamics of the phase singularities,and the spatial distribution of acoustic pressure,etc.This research provides insight to the inhomogeneous coupling of AVBs with both propagating Bloch waves and localized Anderson modes,and may facilitate development of novel OAM-based acoustic devices for active sound field manipulation.
查看更多>>摘要：A model with three-layer structure is introduced to explore the acoustic radiation force(ARF)on composite particles with an elastic thin shell.Combing acoustic scattering of cylinder and the thin-shell theorem,the ARF expression was derived,and the longitudinal and transverse components of the force and axial torque for an eccentric liquid-filled composite particle was obtained.It was found that many factors,such as medium properties,acoustic parameters,eccentricity,and radius ratio of the inner liquid column,affect the acoustic scattering field of the particle,which in turn changes the forces and torque.The acoustic response varies with the particle structures,so the resonance peaks of the force function and torque shift with the eccentricity and radii ratio of particle.The acoustic response of the particle is enhanced and exhibits higher force values due to the presence of the elastic thin shell and the coupling effect with the eccentricity of the internal liquid column.The decrease of the inner liquid density may suppress the high-order resonance peaks,and internal fluid column has less effects on the change in force on composite particle at ka＞3,while limited differences exist at ka＜3.The axial torque on particles due to geometric asymmetry is closely related to ka and the eccentricity.The distribution of positive and negative force and torque along the axis ka exhibits that composite particle can be manipulated or separated by ultrasound.Our theoretical analysis can provide support for the acoustic manipulation,sorting,and targeting of inhomogeneous particles.
查看更多>>摘要：For investigating efficiently the stagnation kinetic-process of Z-pinch,we develop a novel modified electrostatic im-plicit particle-in-cell algorithm in radial one-dimension for Z-pinch simulation in which a small-angle cumulative binary collision algorithm is used.In our algorithm,the electric field in z-direction is solved by a parallel electrode-plate model,the azimuthal magnetic field is obtained by Ampere's law,and the term for charged particle gyromotion is approximated by the cross product of the averaged velocity and magnetic field.In simulation results of 2 MA deuterium plasma shell Z-pinch,the mass-center implosion trajectory agrees generally with that obtained by one-dimensional MHD simulation,and the plasma current also closely aligns with the external current.The phase space diagrams and radial-velocity probability distributions of ions and electrons are obtained.The main kinetic characteristic of electron motion is thermal equilibrium and oscillation,which should be oscillated around the ions,while that of ion motion is implosion inwards.In the region of stagnation radius,the radial-velocity probability distribution of ions transits from the non-equilibrium to equilibrium state with the current increasing,while of electrons is basically the equilibrium state.When the initial ion density and current peak are not high enough,the ions may not reach their thermal equilibrium state through collisions even in its stagnation phase.
查看更多>>摘要：The spatial distributions of different kinds of ions are usually not completely the same in the process of extracting.In order to study the reason for the different characteristics of ion extraction,a simplified simulation model of Cu+and Cr+ions extraction process was established by 2D3V(two-dimensional in space and three-dimensional in velocity space)particle-in-cell(PIC)method.The effects of different extraction voltages from 0 V to 500 V on the density distribution of Cu+and Cr+ions and the change of plasma emission surface were analyzed.On the basis of this model,the ion density distribution characteristics of Cu+ions mixed with Li+,Mg+,K+,Fe+,Y+,Ag+,Xe+,Au+,and Pb+ions respectively under 200-V extraction voltage are further simulated,and it is revealed that the atomic mass of the ions is the key reason for different ion density distributions when different kinds of ions are mixed and extracted,which provides support for further understanding of ion extraction characteristics.
查看更多>>摘要：Simulations are conducted on capacitively coupled Ar/O2 mixed gas discharges employing a one-dimensional fluid coupled with an electron Monte Carlo(MC)model.The research explores the impact of different O2 ratio and pressures on the discharge characteristics of Ar/O2 plasma.At a fixed Ar/O2 gas ratio,with the increasing pressure,higher ion densities,as well as a slight increase in electron density in the bulk region can be observed.The discharge remains dominated by the drift-ambipolar(DA)mode,and the flux of O(3P)at the electrode increases with the increasing pressure due to higher background gas density,while the fluxes of O(1D)and Ar*decrease due to the pronounced loss rate.With the increasing proportion of O2,a change in the dominant discharge mode from α mode to DA mode can be detected,and the O2-associated charged particle densities are significantly increased.However,Ar+density shows a trend of increasing and then decreasing,while for neutral fluxes at the electrode,Ar*flux decreases,and O(3P)flux increases with the reduced Ar gas proportion,while trends in O(1D)flux show slight differences.The evolution of the densities of the charged particle and the neutral fluxes under different discharge parameters are discussed in detail using the ionization characteristics as well as the transport properties.Hopefully,more comprehensive understanding of Ar/O2 discharge characteristics in this work will provide a valuable reference for the industry.
查看更多>>摘要：Based on the substitution rule and symmetry,we propose a method to generate an octagonal quasilattice consisting of square and rhombus tiles.Local configurations and Ammann lines are used to guide the growth of the tiles in a quasiperiodic order.The structure obtained is a perfect eight-fold symmetric quasilattice,which is confirmed by the radial distribution function and the diffraction pattern.
查看更多>>摘要：The effect of undercooling △T and the interface energy anisotropy parameter ε4 on the shape of the equiaxed dendritic tip has been investigated by using a quantitative phase-field model for solidification of binary alloys.It was found that the tip radius p increases and the tip shape amplitude coefficient A4 decreases with the increase of the fitting range for all cases.The dendrite tip shape selection parameter σ*decreases and then stabilizes with the increase of the fitting range,and σ*increases with the increase of ε4.The relationship between σ* and ε4 follows a power-law function σ* ∝ εα4,and α is independent of △T but dependent on the fitting range.Numerical results demonstrate that the predicted σ*is consistent with the curve of microscopic solvability theory(MST)for ε4＜0.02,and σ* obtained from our phase-field simulations is sensitive to the undercooling when ε4 is fixed.
查看更多>>摘要：Recent experimental advancements reported a chemical reaction between antimony and nitrogen under high temper-ature and high pressure,yielding crystalline antimony nitride(Sb3N5)with an orthorhombic structure.Motivated by this statement,we calculate the stability,elastic properties,electronic properties and energy density of the Cmc21 structure for pnictogen nitrides X3N5(X=P,As,Sb,and Bi)using first-principles calculations combined with particle swarm opti-mization algorithms.Calculations of formation enthalpies,elastic constants and phonon spectra show that P3N5,As3N5 and Sb3N5 are thermodynamically,mechanically and kinetically stable at 35 GPa,whereas Bi3N5 is mechanically and kinetically stable but thermodynamically unstable.The computed electronic density of states shows strong covalent bond-ing between the N atoms and the phosphorus group atoms in the four compounds,confirmed by the calculated electronic localization function.We also calculate the energy densities for Sb3N5 and find it to be a potentially high-energy-density material.
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