High-order harmonic generation of ZnO crystals in chirped and static electric fields

High harmonic generation in ZnO crystals under chirped single-color field and static electric field are investigated by solving the semiconductor Bloch equation(SBE). It is found that when the chirp pulse is introduced, the interference structure becomes obvious while the harmonic cutoff is not extended. Furthermore, the harmonic efficiency is improved when the static electric field is included. These phenomena are demonstrated by the classical recollision model in real space affected by the waveform of laser field and inversion symmetry. Specifically, the electron motion in k-space shows that the change of waveform and the destruction of the symmetry of the laser field lead to the incomplete X-structure of the crystal-momentum-resolved(k-resolved) inter-band harmonic spectrum. Furthermore, a pre-acceleration process in the solid four-step model is confirmed.

Exact solutions and localized excitations of a (3+1)-dimensional Gross-Pitaevskii system

Periodic wave solutions and solitary wave solutions to a generalized （3＋1）-dimensional Gross Pitaevskii equation with time-modulated dispersion, nonlinearity, and potential are derived in terms of an improved homogeneous balance principle and a mapping approach. These exact solutions exist under certain conditions via imposing suitable constraints on the functions describing dispersion, nonlinearity, and potential. The dynamics of the derived solutions can be manipulated by prescribing specific time-modulated dispersions, nonlinearities, and potentials. The results show that the periodic waves and solitary waves with novel behaviors are similar to the similaritons reported in other nonlinear systems.

Measurement of^(134)Xe(n,2n)^(133m),gXe reaction cross sections in 14‑MeV region with detailed uncertainty quantification

A lead-shielded HPGe detector and offlineγ-ray spectra of the residual product were used to measure the cross section(CS)and ratios of isomeric CS(σm/σg)in^(134)Xe(n,2n)^(133m),gXe reactions at different energies(13.5 MeV,13.8 MeV,14.1 MeV,14.4 MeV,14.8 MeV)relative to the^(93)Nb(n,2n)^(92)mNb reaction CS.The target was high-purity natural Xe gas under high pressure.The T(d,n)4He reaction produces neutrons.TALYS code(version 1.95)for nuclear reactions was used for calculations,with default parameters and nuclear level density models.The uncertainties in the measured CS data were thoroughly analyzed using the covariance analysis method.The results were compared with theoretical values,evaluation data,and previous experimental findings.CS data of the 134Xe(n,2n)133mXe and 134Xe(n,2n)133gXe reactions and the corresponding isomeric CS ratios at 13.5 MeV,13.8 MeV,and 14.1 MeV neutron energies are reported for the first time.This research advances our knowledge of pre-equilibrium emission in the(n,2n)reaction channel by resolving inconsistencies in the Xe data.

Dynamical analysis,circuit realization,and application in pseudorandom number generators of a fractional-order laser chaotic system

A new five-dimensional fractional-order laser chaotic system(FOLCS)is constructed by incorporating complex variables and fractional calculus into a Lorentz-Haken-type laser system.Dynamical behavior of the system,circuit realization and application in pseudorandom number generators are studied.Many types of multi-stable states are discovered in the system.Interestingly,there are two types of state transition phenomena in the system,one is the chaotic state degenerates to a periodical state,and the other is the intermittent chaotic oscillation.In addition,the complexity of the system when two parameters change simultaneously is measured by the spectral entropy algorithm.Moreover,a digital circuit is design and the chaotic oscillation behaviors of the system are verified on this circuit.Finally,a pseudo-random sequence generator is designed using the FOLCS,and the statistical characteristics of the generated pseudo-random sequence are tested with the NIST-800-22.This study enriches the research on the dynamics and applications of FOLCS.

Research on the Application of VPython 3D Dynamic Visualization in the Teaching of College Physics

As there are numerous physics formulas in addition to them being theoretical,college students generally consider the concepts of physics as abstract,in which they are not able to apply what they have learned.For 3D dynamic animation and visualization in the teaching of college physics,VPyton has many advantages,and it provides useful exploration for students to overcome obstacles in college physics learning.Taking the teaching of simple harmonic vibration,optics,molecular thermal motion,and electric field as examples,this article discusses the application of VPython in the humancomputer interactive teaching mode of college physics,which provides a beneficial exploration and new way to improve students?engineering skills and numeracy,as well as to respond to the national“new engineering education”reform in China.

Dynamic behavior analysis, color image encryption and circuit implementation of a novel complex memristive system

This paper is devoted to introduce a novel four-dimensional memristor-involved system and its applications in image encryption and chaotic circuit. The typical dynamical behaviors of the memristor-involved system are explored, such as chaotic phase potraits, Lyapunov exponent spectrum(LES), bifurcation diagram(BD) and complexity analysis. Then a color image encryption algorithm is designed. In this algorithm, the sequences generated by the four-dimensional memristor-involved system are used in scrambling and diffusion algorithm for three channels.

Self-Similar Solutions of Variable-Coefficient Cubic-Quintic Nonlinear Schr(o|¨)dinger Equation with an External Potential

An improved homogeneous balance principle and self-similar solutions to the cubic-quintic nonlinear Schroedinger and impose constraints on the functions describing dispersion, self-similar waves are presented.

Prediction of heat transfer of nanofluid on critical heat flux based on fractal geometry

Analytical expressions for nucleate pool boiling heat transfer of nanofluid in the critical heat flux （CHF） region are derived taking into account the effect of nanoparticles moving in liquid based on the fractal geometry theory. The proposed fractal model for the CHF of nanofluid is explicitly related to the average diameter of the nanoparticles, the volumetric nanoparticle concentration, the thermal conductivity of nanoparticles, the fractal dimension of nanoparticles, the fractal dimension of active cavities on the heated surfaces, the temperature, and the properties of the fluid. It is found that the CHF of nanofluid decreases with the increase of the average diameter of nanoparticles. Each parameter of the proposed formulas on CHF has a clear physical meaning. The model predictions are compared with the existing experimental data, and a good agreement between the model predictions and experimental data is found. The validity of the present model is thus verified. The proposed fractal model can reveal the mechanism of heat transfer in nanofluid.

Standing,Periodic and Solitary Waves in (1+1)-Dimensional Caudry-Dodd-Gibbon-Sawada-Kortera System

In the paper, the variable separation approach, homoclinic test technique and bilinear method are successfullyextended to a (1+1)-dimensional Caudry-Dodd-Gibbon-Sawada-Kortera (CDGSK) system, respectively.Basedon the derived exact solutions, some significant types of localized excitations such as standing waves, periodic waves,solitary waves are simultaneously derived from the (1+1)-dimensional Caudry-Dodd-Gibbon-Sawada-Kortera systemby entrancing appropriate parameters.

Exact projective solutions of a generalized nonlinear Schrdinger system with variable parameters

A direct self-similarity mapping approach is successfully applied to a generalized nonlinear Schroedinger （NLS） system. Based on the known exact solutions of a self-similarity mapping equation, a few types of significant localized excitation with novel properties are obtained by selecting appropriate system parameters. The integrable constraint condition for the generalized NLS system derived naturally here is consistent with the known compatibility condition generated via Painleve analysis.

Ground-State Properties of Superfluid Fermi Gas in Fourier-Synthesized Optical Lattices

By employing the balance condition between the lattice potential and the interatomic interaction, we study the ground state solutions of superfluid Fermi gases in Fourier-synthesized （FS） optical lattices. The average energy of the ground state, the atoms number, and the atom density distribution of the Fermi system are analytically derived along the Bose–Einstein condensation （BEC） side to the Bardeen–Cooper–Schrieffer （BCS） side. We analyze the properties of ground state solutions at both the BEC limit and unitarity in FS optical lattices. It is found that the relative phase α between the two lattice harmonics impacts greatly on the properties of the ground state of the superfluid Fermi gas. Especially in the BCS limit, when α=π/2, the average energy presents an exponential form with the increase of the potential depth of the lattice harmonics v2. Meanwhile, there exits a minimal value. Moreover, due to the Fermi pressure, the atom density distribution at unitarity is more outstretched than that in the BEC limit. The average energy at unitarity is apparently larger than that in the BEC limit. The properties of the ground state solution exhibit very different behaviors when the system transits from the BEC side to the BCS side.

High-rate performance and super long-cycle stability of Na_(3)V_(2)(PO_(4))_(3)cathode material coated by diatomic doped carbon

Na_(3)V_(2)(PO_(4))_(3)is considered as one of the most promising cathodes for sodium ion batteries due to its excellent thermal stability,long cycle life and high energy density.However,the inferior intrinsic electronic conductivity which brings about the poor rate capability and cycling performance hinders its commercial application.Herein,the S-N co-doped carbon-coated Na_(3)V_(2)(PO_(4))_(3)(NVP@SNC)has been synthesized to resolve the problem.The prepared NVP@SNC forms a hierarchical structure assembled with nanosheets,which is in favor of the electrolyte infiltration and shortening the Na^(+)transmission distance.Numerous lattice defects can be induced in carbon layer by the co-doped elements(S-N),which reduce the Na^(+)diffusion energy barriers and provide adequate Na^(+)migration channels,thus jointly boosting the Na^(+)diffusion coefficient.Consequently,the NVP@SNC cathode shows a high reversible capacity with outstanding rate performance and super long-cycle stability.When discharged at 2.0C,it delivers the capacity near to the theoretical value with a capacity retention of 88.7%after 400cycles.Even if the current is as high as 50.0C,a high capacity of 58.6 mAh·g^(-1)has been released,and41.4 mAh·g^(-1)has been remained after the super long cycling of 4000 circles.This study is expected to supply a new thought of developing high-performance cathodes by diatomic doping for sodium ion battery.

Weak signal detection and adaptive synchronous stability of a novel fifth-order memristive circuit system

This paper is devoted to introduce a novel complex fifth-order memristive circuit system and its applications in synchronous stability and weak signal detection.Firstly,the typical dynamical behaviors of the memristive system are discussed by chaotic phase portrait,complexity analysis,one-parameter bifurcation and Lyapunov exponent spectrum.Secondly,the adaptive control method is applied to realize the synchronization between the drive memristive system(DMS) and the response memristive system(RMS).The results indicate that the synchronization method has strong robustness and anti-interference ability.Thirdly,the weak signal detection of the novel five-dimensional memristive system is realized by using the extreme sensitivity of chaotic system to initial values.Finally,the fifth-order memristive circuit is designed by using basic electronic elements and simulated by Multisim software.And the anti-interference ability and sensitivity of the fifth-order memristive circuit are further verified by adding different weak disturbance signals at different positions of the circuit.

Cross-sections for(n,2n),(n,α),(n,p),(n,d),and(n,t)reactions on molybdenum isotopes in the neutron energy range of 13 to 15 MeV

Given the insufficient cross-sectional data regarding the 14-MeV-neutron experiment of molybdenum,the vital fusion reactor structural material,and the significant heterogeneities among the reported values,this study examined the(n,2n),(n,α),(n,p),(n,d),and(n,t)reaction cross sections in molybdenum isotopes based on the neutrons produced via a T(d,n)4He reaction carried out in the Pd-300 Neutron Generator at the China Academy of Engineering Physics(CAEP).A high-resolution gamma-ray spectrometer,which was equipped with a coaxial high-purity germanium detector,was used to measure the product nuclear gamma activities.In addition,27Al(n,α)24Na and 93Nb(n,2n)92mNb reactions were utilized as the neutron fluence standards.The experimental 92Mo(n,2n)91Mo,94Mo(n,2n)93mMo,100Mo(n,2n)99Mo,98Mo(n,α)95Zr,100Mo(n,α)97Zr,92Mo(n,p)92mNb,96Mo(n,p)96Nb,97Mo(n,p)97Nb,98Mo(n,p)98mNb,92Mo(n,d)91mNb,and 92Mo(n,t)90Nb reaction cross sections were acquired within the 13-15 MeV neutron energy range.Thereafter,we compared and analyzed these obtained cross sections based on the existing IAEA-EXFOR database-derived experimental data,together with evaluation results corresponding to ENDF/B-Ⅷ.0,JEFF-3.3,BROND-3.1,and CENDL-3.1 and the theoretical outcomes acquired through TALYS-1.95 and EMPIRE-3.2.3(nuclear-reaction modeling tools).

Cross-section measurements of(n,2n)and(n,p)reactions on ^(124,126,128,130,131,132)Xe in the 14 MeV region and theoretical calculations of their excitation functions

The reaction cross-sections of ^(124)Xe(n,2n)^(123)Xe,^(126)Xe(n,2n)^(125)Xe,^(128)Xe(n,2n)^(127)Xe,^(130)Xe(n,2n)^(129)mXe,^(132)Xe(n,2n)^(131)mXe,^(130)Xe(n,p)^(130)I,^(131)Xe(n,p)^(131)I,and ^(132)Xe(n,p)^(132)I were measured at the 13.5,13.8,14.1,14.4,and 14.8 MeV neutron energies.The monoenergetic neutrons were generated via the ^(3)H(d,n)^(4)He reaction at the China Academy of Engineering Physics using the K-400 Neutron Generator with a solid ^(3)H-Ti target.A high-purity germanium detector was employed to measure the activities of the product.The reactions ^(93)Nb(n,2n)^(92m)Nb and ^(27)Al(n,α)^(24)Na were adopted for neutron flux calibration.The cross sections of the(n,2n)and(n,p)reactions of the xenon isotopes were obtained within the 13-15 MeV neutron energy range.These cross-sections were then compared with the IAEA-exchange format(EXFOR)database-derived experimental data,together with the evaluation results of the CENDL-3,ENDF/B-Ⅷ.0,JENDL-4.0,RUSFOND,and JEFF-3.3 data libraries,as well as the theoretical excitation function obtained using the TALYS-1.95 code.The cross-sections of the reactions(except for the ^(124)Xe(n,2n)^(123)Xe and ^(132)Xe(n,p)^(132)I)at 13.5,13.8,and 14.1 MeV are reported for the first time in this study.The obtained results are beneficial in providing better cross-section constraints for the reactions in the 13-15 MeV region,thus improving the quality of the corresponding database.Meanwhile,these data can also be used for the verification of relevant nuclear reaction model parameters.

New cross-section measurements for the (n, 2n), (n, p), and (n, a) reactions on bromine in the 14 MeV region with detailed uncertainty quantification

Measurement of the cross-sections of the ^(79)Br(n,2n)^(78)Br,^(81)Br(n,p)^(81)mSe,^(81)Br(n,α)^(78)As,and ^(79)Br(n,α)^(76)As reactions was performed at specific neutron energies,precisely,13.5±0.2,14.1±0.2,14.4±0.2,and 14.8±0.2 MeV,relative to the standard ^(93)Nb(n,2n)^(92)mNb and ^(27)Al(n,α)^(24)Na reference reactions using offlineγ-ray spectrometry and neutron activation.Monoenergetic neutrons were generated at the China Academy of Engineering Physics via a ^(3)H(d,n)^(4)He reaction using the K-400 Neutron Generator equipped with a solid ^(3)H-Ti based target.The activity of the reaction produce was obtained using a high-purity germanium detector.The cross-sections of the(n,2n),(n,p),and(n,α)reactions on the bromine isotopes were measured in the 13–15 MeV neutron energy range.The covariance analysis approach was employed for a thorough inspection of any uncertainties within the measured cross-section data.A discussion and comparison of the observed outcome were carried out with previously published data,especially with the results of the JENDL-4.0,JEFF-3.3,TENDL-2019,and ENDF/B-VIII.0 data libraries,along with the theoretical excitation function curve derived by employing the TALYS-1.95 program.Improved cross-section restrictions for the investigated processes in the 13–15 MeV neutron energy range will be obtained using the current findings,which will help to raise the caliber of associated databases.Furthermore,the parameters of relevant nuclear reaction models can be verified using this data.

Machine learning-based detection of cervical spondylotic myelopathy using multiple gait parameters

Cervical spondylotic myelopathy(CSM)is the main cause of adult spinal cord dysfunction,mostly appearing in middle-aged and elderly patients.Currently,the diagnosis of this condition depends mainly on the available imaging tools such as X-ray,computed tomography and magnetic resonance imaging(MRI),of which MRI is the gold standard for clinical diagnosis.However,MRI data cannot clearly demonstrate the dynamic characteristics of CSM,and the overall process is far from costefficient.Therefore,this study proposes a new method using multiple gait parameters and shallow classifiers to dynamically detect the occurrence of CSM.In the present study,45 patients with CSM and 45 age-matched asymptomatic healthy controls(HCs)were recruited,and a three-dimensional(3D)motion capture system was utilized to capture the locomotion data.Furthermore,63 spatiotemporal,kinematic,and nonlinear parameters were extracted,including lower limb joint angles in the sagittal,coronal,and transverse planes.Then,the Shapley Additive exPlanations(SHAP)value was utilized for feature selection and reduction of the dimensionality of features,and five traditional shallow classifiers,including support vector machine(SVM),logistic regression(LR),k-nearest neighbor(KNN),decision tree(DT),and random forest(RF),were used to classify gait patterns between CSM patients and HCs.On the basis of the 10-fold cross-validation method,the highest average accuracy was achieved by SVM(95.56%).Our results demonstrated that the proposed method could effectively detect CSM and thus serve as an automated auxiliary tool for the clinical diagnosis of CSM.

Bose–Einstein condensates with tunable spin–orbit coupling in the two-dimensional harmonic potential: The ground-state phases, stability phase diagram and collapse dynamics

We study the ground-state phases,the stability phase diagram and collapse dynamics of Bose–Einstein condensates(BECs)with tunable spin–orbit(SO)coupling in the two-dimensional harmonic potential by variational analysis and numerical simulation.Here we propose the theory that the collapse stability and collapse dynamics of BECs in the external trapping potential can be manipulated by the periodic driving of Raman coupling(RC),which can be realized experimentally.Through the high-frequency approximation,an effective time-independent Floquet Hamiltonian with two-body interaction in the harmonic potential is obtained,which results in a tunable SO coupling and a new effective two-body interaction that can be manipulated by the periodic driving strength.Using the variational method,the phase transition boundary and collapse boundary of the system are obtained analytically,where the phase transition between the spin-nonpolarized phase with zero momentum(zero momentum phase)and spin-polarized phase with non-zero momentum(plane wave phase)can be manipulated by the external driving and sensitive to the strong external trapping potential.Particularly,it is revealed that the collapsed BECs can be stabilized by periodic driving of RC,and the mechanism of collapse stability manipulated by periodic driving of RC is clearly revealed.In addition,we find that the collapse velocity and collapse time of the system can be manipulated by periodic driving strength,which also depends on the RC,SO coupling strength and external trapping potential.Finally,the variational approximation is confirmed by numerical simulation of Gross–Pitaevskii equation.Our results show that the periodic driving of RC provides a platform for manipulating the ground-state phases,collapse stability and collapse dynamics of the SO coupled BECs in an external harmonic potential,which can be realized easily in current experiments.

Neurons-system-like structured SnS_(2)/CNTs composite for high-performance sodium-ion battery anode

Sodium-ion batteries(SIBs)have attracted significant attention with respect to renewable energy power generation systems because of the abundant reserves of sodium on earth.However,anode materials are presently limited by low energy density,poor rate performance and inferior cycling stability.In recent years,tin disulfide(SnS_(2))with a particular layered structure has been considered as a promising anode material for SIBs due to its high theoretical capacity and low cost.Herein,a nervoussystem-like structured SnS_(2)/CNTs composite was successfully synthesized via a hydrothermal method.The SnS_(2)sheets were strung with carbon nanotubes(CNTs)to form a hierarchical porous structure,which is effective for electrolyte diffusion and electronic transmission.The large distance of the(001)plane(0.5899 nm)of SnS_(2)favors Na+insertion-extraction dynamics.Benefitting from these structural characteristics,SnS_(2)/CNTs electrodes exhibit high specific capacity,excellent rate performance and superior cycling stability.A high charge capacity of 642 mAh·g^(-1)was released at 0.2 A·g^(-1),and then,a high reversible capacity of 427 mAh·g^(-1)was retained after 100 cycles.Even charged at 2 A·g^(-1),the SnS_(2)/CNTS electrode maintained a capacity of 282 mAh·g^(-1).The nervous-system-like structure of the SnS_(2)/CNTs composite provides a novel strategy for the development of SIBs with high electrochemical performance.

Vector Breathers in an Averaged Dispersion-Managed Birefringent Fiber System

A variable-coefficient coupled nonlinear Schrodinger equation in an averaged dispersion-managed birefringent fiber is investigated. Based on the one-to-one correspondence between variable-coefficient and constant-coefficient equations, an analytical breather solution is derived. As an example to exhibit dynamical behaviors of solution, its controllable excitations including rear excitation, peak excitation and initial excitation are discussed.