Modern Physics Letters B

Sn precursor layer was evaporated on a glass substrate by an electron-beam evaporation method and followed by selenization using Se powder. SnSe film was successfully prepared by adjusting the selenization temperature and selenization time. The phase, microstructure and optical properties of the SnSe films were studied by X-ray diffraction, Raman spectroscopy, Scanning Electron Microscopy, and UV-Vis-NIR spectrophotometer. The results demonstrated that the pure phase polycrystalline SnSe films with a band gap of 0.93 eV could be prepared by selenizing at 450${}^{\circ }$C for 60 min. Under the irradiation of a 980 nm laser with a power of 2 mW/cm², photoelectric response characteristics of the SnSe films were tested, and the response time and recovery time of the prepared film were 62 ms and 80 ms, respectively, indicating that the SnSe film had a large application prospect in near-infrared light detection.

Under investigation in this paper is the generalized Konopelchenko–Dubrovsky–Kaup-Kupershmidt equation. Based on bilinear method, the multiple rogue wave (RW) solutions and the novel multiple soliton solutions are constructed by giving some specific activation functions for the considered model. By means of symbolic computation, these analytical solutions and corresponding rogue wave solutions are obtained via Maple 18 software. The exact lump and RW solutions, by solving the under-determined nonlinear system of algebraic equations for the specified parameters, will be constructed. Via various three-dimensional plots and density plots, dynamical characteristics of these waves are exhibited.

Unsteady flows in the field of engineering are usually calculated by the Unsteady Reynolds-Averaged Navier–Stokes (URANS) owing to the low requirements for computational efforts. However, the numerical resolution of URANS, especially in predicting the unsteady wake flows and sound, is still questionable. In this work, unsteady flow and sound calculations of a circular cylinder are carried out using Improved Delayed Detached Eddy Simulation (IDDES) and the Ffowcs Williams–Hawkings (FW-H) analogy. The predicted results of this calculation are compared with those from the previous studies in the literature in terms of the mean and RMS of the velocity components as well as the sound pressure. The results show that IDDES retains much of the numerical accuracy of the Large Eddy Simulation (LES) approach in predicting unsteady flows and noise while requiring a reduced computational resources in comparison to LES. It is believed that the IDDES can be applied to calculate the complex unsteady flows and flow generated sound with reasonable accuracy in engineering field, which can be used as a promising method for scale-resolving simulations to avoid the expensive computational requirements of LES.

Considering the effect of driver’s expectation and the electronic throttle (ET), an improved two-lane continuum model is proposed. The linear stability condition of the new model is obtained by using the linear stability theory. The nonlinear analysis method is used to study the evolution process of traffic density wave near the neutral stability curve, and the improved KdV-Burgers equation is obtained. The numerical simulation analysis of the improved traffic flow model is carried out to further study how the changes of the expected effect of drivers affect the vehicle speed, the density of traffic flow, vehicle fuel consumption and exhaust emissions. Numerical results demonstrate that the new continuum model presented herein can well describe the developments of shock waves and rarefaction waves, and considering the factor of driver’s expectation and ET effect has a positive impact on the dynamic characteristic of macroscopic flow.

The structural evolutionary behaviors of AgN₃ have been studied by using the particle swarm optimization structure search method combined with the density functional theory. One stable high-pressure metal polymeric phase with the $P\overline{1}$ space group is suggested. The enthalpy difference analysis indicates that the Ibam-AgN₃ phase will transfer to the I4/mcm-AgN₃ phase at 4.7 GPa and then to the $P\overline{1}$-AgN₃ phase at 24 GPa. The $P\overline{1}$-AgN₃ structure is composed of armchair–antiarmchair N-chain, in which all the N atoms are sp² hybridization. The inherent stability of the armchair–antiarmchair chain and the anion–cation interaction between the N-chain and Ag atom induce a high stability of the $P\overline{1}$-AgN₃ phase, which can be captured at ambient conditions and hold its stable structure up to 1400 K. The exhibited high energy density (1.88 KJ/g) and prominent detonation properties ($V_d=12.37$ Km/s; $P_d=10.63$ GPa) of the $P\overline{1}$-AgN₃ phase make it a potentially high energy density material.

The structural properties of Vanadium Ferrite VFe₂O₄ are reported for temperature range 0–1000 K using Density Functional Theory. A comparative study with the available experimental and theoretical data in the literature is also presented. Effects of temperature on lattice constant, volume and bulk modulus are deduced that with the increase in temperature, bulk modulus decreases and lattice constant slightly increases. This proves that the material VFe₂O₄ remains in the same cubic phase for temperature range 0–1000 K. In addition, the optical response is observed with six optical constants like absorption, reflectivity, eloss, dielectric functions, refraction and optical conductivity. Band structures and electronic density of states are also computed by using TB-mBJ potential. We hope that our findings would provide a help to experimentalists in fabricating VFe₂O₄ for temperature-sensitive optical devices.

In recent years, soliton molecules have received reinvigorating scientific interests in physics and other fields. Soliton molecules have been successfully found in optical experiments. In this paper, we attribute the solutions of the (3+1)-dimensional B-type Kadomtsev–Petviashvili (BKP) equation by employing the bilinear method. Based on the $N$-soliton solutions, we establish the soliton molecules, asymmetric solitons and some novel hybrid solutions of this equation by means of the velocity resonance mechanism and the long wave limit method. Finally, we give dynamic graphs of soliton molecules, asymmetric solitons and some novel hybrid solutions.

In this paper, we study exact solutions of the generalized shallow water wave equation. Based on the bilinear equation, we get $N$-solitary wave solutions. For special parameters, we find $N$-fusionable wave solutions. For complex parameters, periodic wave solutions and elastic interactional solutions of solitary waves with periodic waves are obtained. The properties of obtained exact solutions are also analyzed theoretically and graphically by using asymptotic analysis.

Photoluminescence properties of ${\mathrm{\text{Ca}}}_4{\mathrm{\text{Ga}}}_2{\mathrm{\text{S}}}_7:{\mathrm{\text{Eu}}}^{2+}$ chalcogenide semiconductors have been studied under the impulse laser excitation in the range of 10–10⁵ W/cm² at room temperature. This study has shown that as a result of excitation, photoluminescence of ${\mathrm{\text{Ca}}}_4{\mathrm{\text{Ga}}}_2{\mathrm{\text{S}}}_7:{\mathrm{\text{Eu}}}^{2+}$ is characterized by the emission in the interval of 450–575 nm with significant domination in the spectra line at 660 nm. Photoluminescence of ${\mathrm{\text{Ca}}}_4{\mathrm{\text{Ga}}}_2{\mathrm{\text{S}}}_7:{\mathrm{\text{Eu}}}^{2+}$ quenches at wavelengths of 560 nm and 660 nm with constant time frames 258 ns and 326 ns, respectively. Moreover, the temperature measurements of photoluminescence were performed on the samples in the temperature range of 10–300 K.

In this paper, several four-quantum-dot topological structures are designed. The influence of the interdot coupling strength and intradot Coulomb interactions on the conductance is discussed. The location of the anti-resonance band can be manipulated by tuning the interdot coupling strength, which suggests a physical scheme of an effective quantum switch. The Fano anti-resonance peak may evolve into a resonance peak. For the particular value of the interdot coupling strength, two Fano anti-resonances collapse and bound states in the continuum are formed. Moreover, many-body effect makes the number of anti-resonance bands increase. This study provides a theoretical basis for the design of quantum computing devices.

In this paper, based on a multi-layer network consisting of a social network and a physical contact network, we propose a microscopic Monte Carlo simulation model to reproduce the interaction and spread phenomena in the crowd from complex network perspective. The model mainly is used to reproduce the epidemic spread in the situation that the crowd becomes panic showing preventive control behaviors. This coupled microscopic simulation model considers variable infectious rate, recovery rate, panic heterogeneity and preventive measures suitable for studying different actual scenarios. Under the proposed framework, we can take quantitative analysis to measure the influences of various infectious rate, recovery rate, network structure and preventive measures on the spreading of diseases and panic. By comparing a large number of statistical results of the simulation experiments to study different scenarios, it is displayed that the established micro-simulation framework has certain advantages in scalability to consider more different actual scenarios and facilitating the researchers to grasp the global trend to learn what consequences the individual behavior will make.

In this paper, the time-space fractional Casimir equation for the Ito system with conformal fractional derivative is taken into consideration and the corresponding traveling wave solutions are given and the effects of the fractional order to the peakon soliton solution are also discussed and analyzed. In addition, some graphical representations are also provided to show the properties of the solution directly.

An ultra-thin waterborne acoustic metamaterial (AM), which is made of steel and composed of multi-Helmholtz resonators (MHRs), is proposed to achieve perfect sound absorption at low frequencies, which are generated around the resonance mode. The average surface acoustic impedance of the metamaterial is almost perfectly matched with water impedance under the action of resonance among the HRs, thus the perfect sound absorption is achieved. The case of two resonators is taken as an example to verify the design idea. By adjusting HRs’ sizes in simulation, the sound absorption coefficient reaches 99.6% at low frequency of 2740 Hz with ultra-thin thickness less than $\lambda /14$. The abnormal physical properties of AMs are often accompanied by abnormal effective material parameters, which turn to be negative near the perfect sound absorption through inversion calculation. The HRs proposed are simple to fabricate, mechanically stable, and convenient to couple with other resonators to achieve low-frequency broadband sound absorption.

In this paper, we study the effect of the axial deformation of carbon nanotubes in the zigzag and armchair directions on the stability of the interface between hydrogenated and non-hydrogenated regions. We analyze the specific energy of this interface as a function of the axial strain. We found that the clear interface can be obtained at a wider temperature range due to tube stretching. The energy barriers characterizing the process of hydrogen migration from the hydrogenated region of the nanotube to the pristine tube are calculated. It is concluded that the tube deformation significantly affects the stability of the system. For some tubes applied strain can qualitatively change the regularity of hydrogenation, changing the sign of the interface energy.

The structural, electronic, elastic, thermodynamic and thermoelectric properties of RhTaZ (Z = Si, Ge and Sn) half-Heusler materials have been studied using density functional theory. We have found that the compounds studied can be experimentally synthesized. Also, RhTaZ (Z = Si, Ge and Sn) alloys exhibit a semiconductor behavior following the Slater–Pauling rule. The elastic properties calculated confirm that our compounds are mechanically stable. Using Debye’s quasi-harmonic model, the thermodynamic properties of these half-Heusler alloys were investigated. For the study of thermoelectric properties, the semi-classical Boltzmann theory, as implemented in the BoltzTraP code, has been used. The high values obtained from the figure of merit for RhTaZ (Z = Si, Ge and Sn) compounds suggest that they are promising candidates for thermoelectric applications at low and high temperatures.

Identifying the nodes that play significant roles in the epidemic spreading process has attracted extensive attention in recent years. Few centrality measures, such as temporal degree and temporal closeness centrality, have been proposed to quantify node importance based on the topological structure of social contact networks. Most methods estimate the importance of a node from a single aspect, e.g. a higher degree in time snapshot graphs, or shorter distances to other nodes along time-respecting paths. However, this may not be the case in the real world. On the one hand, a node with more nodes on its out streams (i.e. downstream) should be more important because it may affect more nodes along its time-stamped contacting paths once it is infected. On the other hand, a node with more nodes in its in streams (i.e. upstream) deserves closer attention, as it has a higher probability of infection by other nodes. We propose a new temporal centrality measure, upstream and downstream centrality (UD-centrality) with two forms of realizations, i.e. a linear UD-centrality (L-UD) and a product UD-centrality (P-UD) to estimate the importance of nodes based on the temporal structures of social contact networks. We compare our L-UD and P-UD to three classic temporal network centralities through simulations on 14 real-world temporal networks based on the susceptible-infected (SI) model. The comparison results show that UD-centrality can more accurately rank the importance of nodes than the baseline centrality measures.