Modern Physics Letters B

The metallic element Mo has almost no solid solubility in copper and can be used as a nucleation particle to refine the grain size and increase the recrystallization temperature of the alloy during solidification. It is expected to obtain copper alloys with good comprehensive properties by reasonably controlling the addition amount of Mo. However, it is difficult to prepare Cu–Mo alloys with uniform structure and there are few related literatures. In this paper, the aluminothermic reaction method, which has the advantages of simple process, low cost, and large size of the prepared alloy, was adopted, and a cluster model with the atomic ratio of Mo and Ni of 1:12 was introduced to design the alloy composition. Here, five alloys with different copper contents were prepared and followed by room temperature rolling with 40%, 60%, and 80% deformation. The results show that the as-cast Cu–Ni–Mo alloys exhibit good formability, have no macroscopic defects and present a small amount of precipitates. With the increase of alloy elements Ni and Mo, the hardness and strength of the alloys increase obviously, while the electrical conductivity decreases gradually. For the rolled alloys, a large number of lamellar deformed structures are formed, the grains are obviously refined, the precipitated phases are broken and the distribution is more uniform, thus the strength and hardness of the alloy increase significantly, the plasticity decrease significantly, while the conductivity changed little. In this study, high-strength samples were obtained, which may be a valuable exploration for the preparation of Cu–Ni–Mo alloy sheets with excellent microstructure and mechanical properties.

This paper comprises the different types of optical soliton solutions of an important Triki–Biswas model equation with beta-time derivative. The beta derivative is considered as a generalized version of the classical derivative. The aforesaid model equation is the generalization of the derivative nonlinear Schrödinger equation that describes the ultrashort pulse propagation with non-Kerr dispersion. The study is carried out by means of a novel beta derivative operator and three efficient integration schemes. During this work, a sequence of new optical solitons is produced that may have an importance in optical fiber systems. These solutions are verified and numerically simulated through soft computation.

In this research work, the effects on the structural and optical properties of e-beam irradiated Al nanoparticles (Al-NPs) by three field sizes, $4.16\times 10^{16}{\mathrm{\text{cm}}}^{-2}$, $1.20\times 10^{17}{\mathrm{\text{cm}}}^{-2}$ and $1.03\times 10^{18}{\mathrm{\text{cm}}}^{-2}$ fluence were studied. As a result of systematic observations, it has been possible to study the effect of electron beam on X-ray diffraction (XRD), infrared (IR) spectroscopy and Raman band modifications and, consequently, on the crystal structure and atomic dynamics of Al-NPs. The XRD method determined that Al-NPs are combined with water molecules in the air to form aluminum hydroxide (Al(OH)₃) groups. The Al(OH)₃ formation was not observed in any of the samples irradiated with three different fluences, $4.16\times 10^{16}{\mathrm{\text{cm}}}^{-2}$, $1.20\times 10^{17}{\mathrm{\text{cm}}}^{-2}$ and $1.03\times 10^{18}{\mathrm{\text{cm}}}^{-2}$, respectively. Confirmation of these results was also shown in the method of IR spectroscopy. While 12 vibrational modes were observed in the non-irradiated samples, only the vibrational modes corresponding to Al–Al bonds were observed in $4.16\times 10^{16}{\mathrm{\text{cm}}}^{-2}$, $1.20\times 10^{17}{\mathrm{\text{cm}}}^{-2}$, and $1.03\times 10^{18}{\mathrm{\text{cm}}}^{-2}$ fluence irradiated samples. It was determined by the Raman spectroscopy method that a low concentration of Al(OH)₃ remains in the samples irradiated with $4.16\times 10^{16}{\mathrm{\text{cm}}}^{-2}$ fluence. Only $1.20\times 10^{17}{\mathrm{\text{cm}}}^{-2}$ and $1.03\times 10^{18}{\mathrm{\text{cm}}}^{-2}$ fluence irradiated samples were found to correspond to the XRD and IR spectra, and Raman vibrational modes corresponding to Al–Al bonds were observed. In addition, electron irradiation is a suitable technique to increase the optical properties of nanoparticles by controlling the size of the particles.

The ZrCuSiAs materials have many interesting physical properties and have been extensively studied in recent decades. Recently, two Mn-based ZrCuSiAs-type pnictides, i.e. ThMnAsN and ThMnPN, have been synthesized in the experiment, which shows the anti-ferromagnetic properties. Motived by the experiment, we here perform a comprehensive investigation on their elastic, electronic, and magnetic properties by the density functional theory and Monte Carlo simulations. Our calculations show that ThMnAsN and ThMnPN are both antiferromagnetic semiconductors. The magnetic ground state of both materials is the $C$-type anti-ferromagnetism and their bandgaps are about 0.47 eV and 0.61 eV for ThMnAsN and ThMnPN, respectively. The Monte Carlo simulated Néel temperatures of ThMnAsN and ThMnPN are 57 K and 55 K, respectively. These results are well consistent with the experimental results. Our work not only reveals the physical essence of the two newly synthesized materials but also could help to the understanding of the magnetic behaviors of other ZrCuSiAs-type compounds.

In order to propose a more realistic epidemic dynamics model and effective medical resource allocation strategy, this paper constructs an improved SEIR model combined with a dynamical medical resource allocation model and individual behavior sharing medical resources. Simultaneously, a genetic algorithm to solve the medical resource allocation model is proposed to obtain the optimum resource allocation strategy. In this SEIR model, there is an important critical value of the stored medical resources, when the number of stored medical resources is more than the critical value, the inhibition of epidemic can be continuously enhanced until it reaches a minimum threshold, and then stabilizes near a minimum value, but when the resource surplus is below the critical value, the inhibitory effect on epidemic will weaken. The results demonstrate that the number of patients in the proposed method decreased more than 40% compared with the conventional control experiment. Moreover, the algorithm can automatically make decisions according to individual behavior in sharing preferences and the epidemic development trend.

Aluminum (Al) nanoparticle (ANP), as a metal fuel agent, has excellent combustion rate and energy density. However, several critical research gaps of ANP still exist. This study is focused on the annealing properties of ANP and its coating performances under the mixture of ethanol and ether molecules. According to those obtained molecular dynamic (MD) simulation results, the microstructure of ANP in the annealing process and the formation of ethanol–ether binary coating are discussed in this paper. During the melting process, the melting point of ANP could be analyzed by the inflection point of its atomic potential energy and the mean square displacement, then the accuracy of EAM force field could be verified. Because surface atoms have lower potential energy than inner atoms, it seems that the melting of ANP started from the particle surface and diffuses from surface to the core. When the melted Al cluster is solidified until 300 K, the microstructure of the crystallized particle is largely affected by the cooling rate. If the cooling rate if too fast, it is not enough for the Al cluster to recrystallize, which is called as the “freezing effect” for ANP. Next, the binary “competitive adsorption” behavior of ethanol and ether on the surface of ANP was simulated according to different ethanol–ether molecular ratios. Analyses of ethanol–ether binary coating layer show that the main component of binary coating is ethanol, but not ether. This competitive superiority of ethanol is caused by its own adsorption mechanism and molecular migration in this mixture of ethanol and ether.

The (3+1)-dimensional Kadomtsev–Petviashvili (KP) equation is studied in this paper by constructing the Hirota bilinear form. The lump solution of the equation is obtained by bilinear form, and the conditions for the existence of the solution are obtained. The picture description of lump solution is further given. On the other hand, we also give the collision phenomena of lump solution, periodic wave solution and a single-kink soliton solution when the (3+1)-dimensional KP equation reduces to $z=y$ and $z=t$ by means of the Hirota method. The collision phenomenon is shown in the 3D plot description, the dynamic characteristics of the collision are also analyzed.

The effects of contact barrier height on performances of Si/BaSi₂ p–n heterojunction, BaSi₂ p–n homojunction and Si/BaSi₂/Si p–i–n heterojunction were numerical calculated. Band energy diagram, built-in electric field, carrier generation and carrier transportation distributed in the devices are comprehensively investigated. BaSi₂ p–n homojunction solar cells are very sensitive to front contact barrier height due to the high light absorption coefficient of front p-BaSi₂ layer. Si/BaSi₂ p–n heterojunction and BaSi₂ p–n homojunction solar cells with donor concentration $(N_D)$ less than $10^{17}{\mathrm{\text{cm}}}^{-3}$ are apparently affected by back contact barrier height. The ideal $\alpha$-Si/BaSi₂/$\alpha$-Si p–n solar cell achieves a high $V_{\mathrm{\text{oc}}}$ of 1.131 V, suggesting a promising and alternative structure to gain excellent BaSi₂-based solar cells once the Urbach tail states and defects can be effectively eliminated. The results help to fundamentally understand operation mechanism and provide intuitive guidance for achieving high-efficiency BaSi₂ solar cells.

In this paper, the effect of dewetted gold nanoparticles (AuNPs) on hexagonal boron nitride (hBN) is discussed along with the changes in surface plasmon resonance (SPR). Au is sputtered on monolayer hBN/SiO₂/Si substrate for a varied duration and subjected to thermal annealing. Monolayer hBN is verified by spectroscopic ellipsometry using the Tauc–Lorentz model, while the AuNPs are modeled using a combination of Gauss, Cody–Lorentz, and Tanguy dispersion laws. Sputtering of Au on hBN/SiO₂/Si results in a film-like layer compared to the one on SiO₂/Si. Before annealing, the improved uniformity of Au on hBN/SiO₂/Si diminished the SPR wavelength, ${\lambda }_{\mathrm{\text{spr}}}$, when the sputter duration exceeded 30 s, much sooner compared to 120 s from the one on SiO₂/Si. After annealing, the ${\lambda }_{\mathrm{\text{spr}}}$ is vibrant for all samples around 2.3 eV. Au dewetted more on hBN due to higher surface tension. Large dewetted AuNPs supported by hBN result in higher photon extinction at ${\lambda }_{\mathrm{\text{spr}}}$. The longest sputter duration of 120 s on hBN/SiO₂/Si (mean size 53 nm) exhibited an 11.2% higher extinction coefficient compared to the one on SiO₂/Si (mean size 39.6 nm). Findings support the advantages of preparing plasmonic AuNPs by dewetting on monolayer hBN.

Tunable band structure and effective spatial separation of carriers are important for designing good optoelectronic devices. In this work, effects of interfacial defect including vacancies and $p$- or $n$-type doping on the band alignment and magnetic and optical properties of g-C₃N₄/WSe₂ van der Waals heterostructures are systematically investigated under the premise of spin-orbit coupling density-functional theory. The results illustrate that the pristine g-C₃N₄/WSe₂ heterostructure exhibits intrinsic type-I band alignment with a direct bandgap of 1.101 eV, and the absorption of UV-visible light can be effectively improved compared with that of isolated WSe₂ and g-C₃N₄ monolayers. The N vacancies as well as $B_C$, $C_N$ and $P_C$ doping produce asymmetrical spin-up and spin-down states, bringing about the magnetization and even magnetic half-metallicity characteristics ($B_C$ and $C_N$ doping). The band edge positions of g-C₃N₄/WSe₂ heterostructure can be also well adjusted by introducing vacancies and $p$- or $n$-type doping in the g-C₃N₄ layer, accompanied by the transition of band alignment from types I to II, which will remarkably promote the separation of photogenerated electron-hole pairs. The defective g-C₃N₄/WSe₂ heterostructures can be considered as a promising candidate for spintronics and optoelectronic devices.

The Lie symmetry method is used to obtain a variety of closed-form wave solutions for the extended (3+1)-dimensional Jimbo–Miwa (JM) Equation, which describes certain interesting higher-dimensional waves in ocean studies, marine engineering, and other fields. By applying the Lie symmetry technique, we explicitly investigate all the possible vector fields, commutation relations of the considered vectors, and various symmetry reductions of the equation. Based on three stages of Lie symmetry reductions, the JM equation is reduced to several nonlinear ordinary differential equations (NLODEs). Consequently, abundant closed-form wave solutions are achieved, including arbitrary functional parameters. Evolutionary dynamics of some analytic wave solutions are demonstrated through three-dimensional plots based on numerical simulation. Consequently, singular soliton, kink waves, periodic oscillating wave profiles, combined singular soliton profiles, curved-shaped multiple solitons, and periodic multiple solitons with parabolic wave profiles are demonstrated by taking advantage of symbolic computation work. The obtained analytical wave solutions, which include arbitrary independent functions and other constants of the governing equation, could be used to enrich the advanced dynamical behaviors of solitary wave solutions. Furthermore, the study of conservation laws is investigated via the Ibragimov technique for Lie point symmetries.

In this work, the new optical soliton solutions and interaction solutions for the space-time fractional Fokas–Lenells equation with fractional $M$-derivatives are constructed via three mathematical analytical techniques, namely the extended SE method, unified solver method, and three-wave methods. The results have proved the efficiency of the suggested techniques for obtaining abundant optical soliton solutions to nonlinear evolution equations (NLEEs) and closed-form solutions in the forms of rational function solutions; hyperbolic and trigonometric function solutions and multi-wave interaction solutions are obtained. These techniques are more efficient, robust, and powerful mathematical tools for acquiring several optical soliton solutions for many other fractional space-time NLEEs that arise in optical physics and plasma physics. The graphical representations of the combined optical solitons are demonstrated using three- and two-dimensional graphics.