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Considering the fact that memristors have the characteristics similar to biological synapses, a fractional-order multistable memristor is proposed in this paper. It is verified that the fractional-order memristor has multiple local active regions and multiple stable hysteresis loops, and the influence of fractional-order on its nonvolatility is also revealed. Then by considering the fractional-order memristor as an autapse of Hindmarsh–Rose (HR) neuron model, a fractional-order memristive neuron model is developed. The effects of the initial value, external excitation current, coupling strength and fractional-order on the firing behavior are discussed by time series, phase diagram, Lyapunov exponent and inter spike interval (ISI) bifurcation diagram. Three coexisting firing patterns, including irregular asymptotically periodic (A-periodic) bursting, A-periodic bursting and chaotic bursting, dependent on the memristor initial values, are observed. It is also revealed that the fractional-order can not only induce the transition of firing patterns, but also change the firing frequency of the neuron. Finally, a neuron circuit with variable fractional-order is designed to verify the numerical simulations.

The magnetic topological van der Waals materials family MnBi2Te4/(Bi2Te3) n have drawn markedly attention due to their novel multiple topological phases in different magnetic configurations. Recently, their close relative, the MnSb4Te7, was firstly synthesized in experiments (2021 Phys. Rev. Lett. 126 246601). To further explore the emergent properties of MnSb4Te7, we have systematically investigated the magnetic and topological characters under compressive strain and charge doping using first-principles calculations. We predict that MnSb4Te7 transits from an interlayer antiferromagnetic ground state to a ferromagnetic semimetal ground state with multiple Weyl points when compressive strained along c axis above 8% or charge doping before 0.1 hole/formula concentration. Notable anomalous Hall conductivity is also predicted. Meanwhile, the magnetic easy axis can be reoriented from out-of-plane to in-plane orientation when strain or electron doping is applied. The underlying magnetic exchange mechanism is also analyzed from our calculation results. Our work thus provides a feasible way to realize applications of the highly tunable magnetic-topological nature and a comprehensive theoretical understanding of this magnetic topological material.

Online dose verification in proton therapy is a critical task for quality assurance. We further studied the feasibility of using a wavelet-based machine learning framework to accomplishing that goal in three dimensions, built upon our previous work in 1D. The wavelet decomposition was utilized to extract features of acoustic signals and a bidirectional long-short-term memory (Bi-LSTM) recurrent neural network (RNN) was used. The 3D dose distributions of mono-energetic proton beams (multiple beam energies) inside a 3D CT phantom, were generated using Monte-Carlo simulation. The 3D propagation of acoustic signal was modeled using the k-Wave toolbox. Three different beamlets (i.e. acoustic pathways) were tested, one with its own model. The performance was quantitatively evaluated in terms of mean relative error (MRE) of dose distribution and positioning error of Bragg peak ( Δ B P ), for two signal-to-noise ratios (SNRs). Due to the lack of experimental data for the time being, two SNR conditions were modeled (SNR = 1 and 5). The model is found to yield good accuracy and noise immunity for all three beamlets. The results exhibit an MRE below 0.6% (without noise) and 1.2% (SNR = 5), and Δ B P below 1.2 mm (without noise) and 1.3 mm (SNR = 5). For the worst-case scenario (SNR = 1), the MRE and Δ B P are below 2.3% and 1.9 mm, respectively. It is encouraging to find out that our model is able to identify the correlation between acoustic waveforms and dose distributions in 3D heterogeneous tissues, as in the 1D case. The work lays a good foundation for us to advance the study and fully validate the feasibility with experimental results.

In view of the fact that the traditional graph model method which only considers statistical features or general semantic features when extracting keywords from existing massive educational resources, lacks the function of mining and utilizing multi-factor semantic features, this paper proposes an improved TextRank-based algorithm for keyword extraction of educational resources. According to the characteristics of Chinese text and the shortcomings of traditional TextRank algorithm, the improved algorithm featuring multi-feature fusion is developed using the importance of words in the corpus, the location information in the text and the attributes of words. Experimental results show that this method has higher accuracy, recall rate, and F-measure value than traditional algorithms in the process of keyword extraction of educational resources, which improves the quality of keyword extraction and is beneficial to better utilization and management of educational resources.

As an important part of the large complex lifeline system, the transmission tower line system has many accidents. Based on the static and dynamic calculation theory, the response of the structure is analyzed, the ultimate capacity of the transmission tower system is obtained, and the weak position is studied, and the ultimate capacity of the transmission line is comprehensively evaluated. The result shows that the weak position is Segment 4 and 5 of the transmission tower, and the ultimate capacity of dynamic analysis is smaller than that of static analysis.

Two-dimensional transition metal dichalcogenide MnSe2 (2D-MnSe2) with Curie temperature approximate to 300 K has a significant spintronic application on thin-film devices. We demonstrate theoretically a tunable magnetic transition of 2D-MnSe2 between anti-ferromagnetic (AFM) metal and ferromagnetic (FM) half metal as strain increasing. Mechanism of that transition involves a competition between d–p–d through-bond and d–d direct interaction in 2D-MnSe2. Hole doping is an alternative way to enhance the stability of FM coupling. Adsorption (including Li, Na, Cl and F) and vacancy (Mn and Se) studies confirm that the controllable magnetism of 2D-MnSe2 is related to both interaction competition and charge doping. Tensile strains can greatly amplify through-bond interaction and exchange parameters, resulting in a sharp increase of Curie temperature.

In order to accelerate the development of large transport aircraft, it is important to build a continuous transonic wind tunnel. The re-import section, acted as a key part of the wind tunnel, plays an important role in maintaining the stability and balance of the wind tunnel. On this account, the structure design and strength check of the re-import section is investigated. Firstly, the 3-D model of re-import section is established based on NX software. Secondly, the layout of stiffeners is optimized to solve the bearing problem of components. Finally, the strength check of the re-import section is carried out based on ABAQUS software to validate the effectiveness of the designed structure.

Many crushing equipment will have particle crushing behavior. Mastering the particle crushing behavior helps improve the performance of crushing equipment. In this paper a numerical model of single-particle crushing has been established in order to investigate the the particle crushing characteristics under static load. The evolution process of particle crushing, size effect, law of energy accumulation and dissipation were comprehensively discussed, respectively. The simulation results showed that when a single particle was crushed, a large number of failure units and acoustic emissions (AE) occurred in the middle of the particle, and single-particle crushing is caused by tensile stress. There is size effect of single particle. By analyzing the characteristics of single particle crushing in crushing equipment, this study can give helpful theoretical support for the optimization of crushing process of crushing equipment, so as to obtain better crushing efficiency and energy saving effect.

Crushing equipment is involved in cement, electric power, nonmetal and other industries. However, the multi-particle crushing behaviors and characteristics are essential to the crushing equipment performance. In this paper a numerical model for multi-particle crushing has been established in order to investigate the behaviors and characteristics of particle crushing. The evolution process of particle crushing, size effect, law of energy accumulation and dissipation were comprehensively discussed. The particle crushing behaviors are remarkable. when multiple particles were crushed, a large number of failure units and acoustic emission (AE) appeared at the top. The energy consumed by multi-particle crushing was low, and multi-particle crushing was more efficient. The particle size is of great importance to the crushing characteristics. The bigger a particle is, the easier the crushing happens. This study could give useful suggestions in the design of the crushing technology.

The field investigation of the seasonal coarse grained frozen soil slopes along the eastern section of the proposed Sichuan-Tibet railway shows that the deformation and failure of the slopes are widespread. In order to explore the deformation characteristics and failure mechanisms of the slopes in this area and provide a basis for the design and protection of the slopes along Sichuan-Tibet railway, laboratory model tests on the seasonal coarse grained frozen soil slopes under snowfall conditions were conducted. The results show that, the deformation and failure of the seasonal coarse grained frozen soil slope are caused by the repeated alternation of the failure of the surface soil structure caused by frost heave and the surface soil saturation caused by snow thaw infiltration, and the reduction of the shear strength of the surface soil under repeated freezing and thawing conditions. The deformation and failure of the seasonal coarse grained frozen soil slopes along the eastern section of the Sichuan-Tibet railway are mainly characterized by creep-flowed, topsoil slip and slippage on slope surface. The emphasis of slope protection in this area are slope thermal insulation and waterproof.

We present Caltech Submillimeter Observatory CO (2-1) and Spitzer IRAC observations toward IRAS 22506+5944, which is a 10$^4$ $L_{\odot}$ massive star-forming region. The CO (2-1) maps show an east-west bipolar molecular outflow originating from the 3 mm dust continuum peak. The Spitzer IRAC color-composite image reveals a pair of bow-shaped tips which are prominent in excess 4.5 $\mu$m emission and are located to the leading fronts of the bipolar outflow, providing compelling evidence for the existence of bow-shocks as the driving agents of the molecular outflow. By comparing our CO (2-1) observations with previously published CO (1-0) data, we find that the CO (2-1)/(1-0) line ratio increases from low (~5 km s$^{-1}$) to moderate (~8 - 12 km s$^{-1}$) velocities, and then decreases at higher velocities. This is qualitatively consistent with the scenario that the molecular outflow is driven by multiple bow-shocks. We also revisit the position-velocity diagram of the CO (1-0) data, and find two spur structures along the outflow axis, which are further evidence for the presence of multiple jet bow-shocks. Finally, power-law fittings to the mass spectrum of the outflow gives power law indexes more consistent with the jet bow-shock model than the wide-angle wind model., Comment: published in Research in Astronomy and Astrophysics

A compact intra-cavity pumped low-threshold passively Q-switched (PQS) Ho:Sc2SiO5 (Ho:SSO) laser is reported for the first time. The Tm:YAlO3 (Tm:YAP) crystal and the Ho:SSO crystal are placed in the same laser cavity. A laser diode with a central wavelength of 793 nm is used to realize the output of the Ho:SSO laser. Both the continuous wave (CW) and PQS operation are investigated. A Cr2+:ZnSe is used as the saturable absorber in the PQS Ho:SSO laser. For the CW mode, the laser threshold is only 750 mW, which is 980 mW in the PQS mode. A maximum pulse energy of 699 µJ is primarily obtained, corresponding to the pulse width of 96 ns. The maximum repetition frequency is 1.46 kHz. The maximum pulse peak power can be calculated to be 7.28 kW. The beam quality factor M 2 is calculated to be 1.4 with the maximum output power.

A cw operation and a passively Q-switched (PQS) Ho:SSO laser (Cr2+:ZnSe as a saturable absorber) end-pumped by a Tm:YAP laser operating at near room temperature are reported. It is the first time to report a PQS Ho:SSO laser. For the cw mode, a maximum cw output power of 3.0 W is obtained, corresponding to a slope efficiency of 31.4%. For the PQS mode, a Cr2+:ZnSe is used as the saturable absorber, with transmission of 88.4% at 2112 nm. A maximum pulse energy of 1.29 mJ is obtained, corresponding to the pulse repetition frequency of 2.42 kHz. In this study, we change the distance between Cr2+:ZnSe and the output mirror to research the pulse characteristic of the PQS Ho:SSO laser. The minimum pulse width of 73.5 ns is obtained, corresponding to the pulse energy of 0.9 mJ and the pulse repetition frequency of 2.65 kHz.

The problem of Aharonov - Bohm (AB) scattering on two parallel flux lines of the same magnitude is solved by the method of path integration.

Typhoon-induced storm surge is the largest threat to the Zhanjiang Coast of the northern South China Sea. In this study, we report on two processes of storm surges generated by Typhoons Rammasun (TR) and Kalmaegi (TK) with similar tracks at this region. Results show that the peak of the storm surge during TK (with a maximum value of 4.50 m) was significantly larger than that during TR (with the maximum value of 2.60 m), although the intensity of TK (Category 4 with 40 m s-1 maximum wind and 960 hPa central air pressure) was much weaker than that of TR (Category 6 with 60 m s-1 maximum wind and 910 hPa central air pressure). Comparisons of the typhoon properties and astronomic tides reveal that the peaks of storm surge were closely related to typhoon maximum wind radius, typhoon moving speed, and tide-surge interaction rather than typhoon intensity during the two cases, indicating complex dynamics of storm surge at the Zhanjiang Coast.

A continuous-wave 0.5 % Ho3+-doped Ho:Sc2SiO5 (Ho:SSO) laser output at 2112 nm pumped by a Tm:YAP laser is reported. The Ho:SSO bulk crystal was grown by the Czochralski technique. A maximum laser power of 3.72 W was obtained with a slope efficiency of 32.9%, when the transmittance of output mirror was 30%. In this experiment, two output mirrors with different transmittance were also researched. The output spectra of Ho:SSO laser with different output mirrors are also given. The M 2 factor is found to be 1.29. In addition, the absorption and emission spectra are given in this paper.