Modern Physics Letters B

We collected data of the surface tension versus the temperature of 28 saturated refrigerant fluids available in the NIST database. These data are used to build a new corresponding state-based correlation. Compared with other previously proposed correlations, the current one has the advantages of both simplicity and accuracy. To check the ability of correlations, we compared the numerically calculated/predicted results with the data in the NIST database. It is found that the average absolute deviations are less than 10% for 26 refrigerants and less than 1% for 8 refrigerants.

This paper aims to compute solitary wave solutions and soliton wave solutions based on the ansatz methods to the perturbed nonlinear Schrödinger equation (NLSE) arising in nano-fibers. The improved $tan(𝜃/2)$-expansion method and the rational extended sinh–Gordon equation expansion method are used for the first time to obtain the new optical solitons of this equation. The obtained results give an accuracy interpretation of the propagation of solitons. We held a comparison between our results and those are in the previous work. The outcome indicates that perturbed NLSE arising nano-fibers is used in optical problems. Finally, via symbolic computation, their dynamic structure and physical properties were vividly shown by three-dimensional, density, and $t$-curves plots. These solutions have greatly enriched the exact solutions of (2+1)-dimensional perturbed nonlinear Schrödinger equation in the existing literatures.

Modern biomedical and tribological systems are increasingly deploying combinations of nanofluids and bioconvecting microorganisms which enable improved control of thermal management. Motivated by these developments, in this study, a new mathematical model is developed for the combined nanofluid bioconvection axisymmetric squeezing flow between rotating circular plates (an important configuration in, for example, rotating bioreactors and lubrication systems). The Buongiorno two-component nanoscale model is deployed, and swimming gyrotactic microorganisms are considered which do not interact with the nanoparticles. Thermal radiation is also included, and a Rosseland diffusion flux approximation is utilized. Appropriate similarity transformations are implemented to transform the nonlinear, coupled partial differential conservation equations for mass, momentum, energy, nanoparticle species and motile microorganism species under suitable boundary conditions from a cylindrical coordinate system into a dimensionless nonlinear ordinary differential boundary value problem. An efficient scheme known as differential transform method (DTM) combined with Padé-approximations is then applied to solve the emerging nonlinear similarity equations. The impact of different non-dimensional parameters i.e. squeezing Reynolds number, rotational Reynolds number, Prandtl number, thermophoresis parameter, Brownian dynamics parameter, thermal radiation parameter, Schmidt number, bioconvection number and Péclet number on velocity, temperature, nanoparticle concentration and motile gyrotactic microorganism density number distributions is computed and visualized graphically. The torque effects on both plates, i.e. the lower and the upper plate, are also determined. From the graphical results, it is seen that momentum in the squeezing regime is suppressed clearly as the upper disk approaches the lower disk. This inhibits the axial flow and produces axial flow retardation. Similarly, by enhancing the value of squeezing Reynolds number, the tangential velocity distribution also decreases. More rigorous squeezing clearly therefore also inhibits tangential momentum development in the regime and leads to tangential flow deceleration. Tables are also provided for multiple values of flow parameters. The numerical values obtained by DTM-Padé computation show very good agreement with shooting quadrature. DTM-Padé is shown to be a precise and stable semi-numerical methodology for studying rotating multi-physical flow problems. Radiative heat transfer has an important influence on the transport characteristics. When radiation is neglected, different results are obtained. It is important therefore to include radiative flux in models of rotating bioreactors and squeezing lubrication dual disk damper technologies since high temperatures associated with radiative flux can impact significantly on combined nanofluid bioconvection which enables more accurate prediction of actual thermofluidic characteristics. Corrosion and surface degradation effects may therefore be mitigated in designs.

To explain the axial fracture phenomenon of Explosively Formed Projectile (EFP), the fracture mechanism of long rod EFP during the forming phase is analyzed by the stress wave theory. When the velocity gradient $\mathrm{\Delta }v$ between the head and tail parts exceeds the critical value $\mathrm{\Delta }{v}_{\mathrm{\text{cr}}}$, the EFP would fracture in the axial direction. Based on the Johnson–Cook constitutive model parameters and the special conditions in the forming phase of EFP, the critical velocity gradient $\mathrm{\Delta }{v}_{\mathrm{\text{cr}}}$ can be determined by theoretical calculation and then validated by experimental results for both copper and tantalum EFPs. The experimental results for EFP’s fracture agree well with the prediction of the theoretical analysis. The theoretical analysis method can be applied as an important measure to determine the critical velocity gradient and predict the fracture of long rod EFP, providing reference for the application of new kinds of high density materials in the EFP research area.

In this paper, two generalized fifth-order nonlinear evolution equations are introduced and investigated: One is (1+1)-dimensional, the other is (2+1)-dimensional. The Hereman–Nuseir method is used to derive the multiple kink solutions and singular kink solutions, and the conditions for the cases of complete integrability of these two equations. Meanwhile, it is found that these equations have completely different dispersion relations and physical structures. The corresponding graphs with specific parameters are given to show the effectiveness and validness of the obtained results.

In this work, a pulsed laser deposition (PLD) technique with an Nd:YAG laser source was used to produce pure Hydroxyapatite (HA) and Cu-substituted HA (Cu-HA) coatings on stainless steel substrates in vacuum at room temperature. It is observed that the combined effects of percentages of Cu dopants and laser energy as well as annealing temperature significantly modify the crystallinity of the films. The morphology and structural properties of the deposited HA films were analyzed by field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), and Raman spectroscopy. FESEM images displayed various shapes of nanoparticles with high-surface density throughout the area of the substrate and with typical sizes around 26–208 nm. XRD analysis confirmed that post-deposition annealing is essential to achieve the desired crystallinity and uniformity of coatings. The Raman spectrum of HA has peaks at 958.22, 437.48, and 587.05 cm${}^{-1}$ attributed to the ${\nu }_1$ PO${}_4^{3-}$, ${\nu }_2$ PO${}_4^{3-}$, and ${\nu }_3$ PO${}_4^{3-}$, respectively. The synthesized HA and Cu-HA crystalline films are nanostructures with dense and compact microstructures. Finally, irregular surface and crystalline structure of fabricated films lead to the extension of the surface and enhance the cell’s proliferation in medical uses and biomedical applications.

To solve the problems of high calculation cost and difficult optimization caused by the complex gas–liquid two-phase flow in liquid ring pumps, an optimization method of a liquid ring pump impeller based on the proper orthogonal decomposition (POD) surrogate model was proposed. The impeller blade shape was parameterized by using the quartic Bezier curve. The sample was obtained from the uniform experimental design of blade shape design parameters. The POD surrogate model was constructed by the parameters of sample blade shape and its corresponding flow field data, which was used instead of CFD numerical simulation to predict the flow field variables under the perturbations of blade design parameters in the optimization process. And then, the gradient vector of the objective function to design variables was predicted quickly and accurately. The blade shape was updated continuously along the negative direction of the gradient vector, and then, the optimal design of the impeller was acquired. The calculation case results show that the relative error between the pressure field in the impeller predicted by the POD method and that of CFD simulation is less than 5%, and the calculation cost is only 1/8460 of CFD simulation. Compared with the original model, the flow field distribution in the optimized model is significantly improved, and the efficiency is promoted by 3.8%.

The DC and AC performances of proton radiated Silicon-Germanium (SiGe) Heterojunction Bipolar Transistors (HBTs) with different emitter areas at liquid nitrogen temperature (77 K), room temperature and heating hotplate (393 K) were presented in this work. Performance dependence on the emitter area and temperature was investigated. Results showed that SiGe HBTs with a large emitter area had more damage by proton radiation. Furthermore, the SiGe HBTs showed better tolerance to proton radiation at extreme temperatures than at room temperature. To reveal the underlying mechanism, the radiated SiGe HBTs were modeled based on the device structure and parameters. The electron density, Shockley–Read–Hall (SRH) recombination and carrier mobility were extracted from the device model and demonstrated to have major impacts on the performance dependence of the radiated SiGe HBTs. The results provide useful guidance for the application of SiGe HBTs at extreme environments.

Based on the generalized dressing method, we propose a new integrable variable coefficient Spin-1 Gross–Pitaevskii equations and derive their Lax pair. Using separation of variables, we have derived explicit solutions of the equations. In order to analyze the characteristic of derived solution, the graphical wave of the solutions is plotted with the aid of Matlab.

This paper is devoted to obtaining the multi-soliton solutions, high-order breather solutions and high-order rational solutions of the (3+1)-dimensional B-type Kadomtsev–Petviashvili (BKP) equation by applying the Hirota bilinear method and the long-wave limit approach. Moreover, the interaction solutions are constructed by choosing appropriate value of parameters, which consist of four waves for lumps, breathers, rouges and solitons. Some dynamical characteristics for the obtained exact solutions are illustrated using figures.

In this work, ${\mathrm{\text{BiFe}}}_{1-x}{\mathrm{\text{Co}}}_x{\mathrm{\text{O}}}_3$ ($x$ = 0, 0.08) nanoparticles were synthesized by the solution method and their structural differences were studied. X-ray diffraction results show that the rhombohedral R3c space group and perovskite structures are detected in both samples, accompanied by an impurity phase. The (104) and (110) peaks merge when cobalt ions are doped. The decrease in lattice parameters indicates that the microstructure of the nanoparticles becomes gradually distorted. Mössbauer spectroscopy analysis at room temperature reveals an additional doublet due to the oxygen vacancies in ${\mathrm{\text{BiFe}}}_{0.92}{\mathrm{\text{Co}}}_{0.08}{\mathrm{\text{O}}}_3$. Hyperfine interactions, spatial spin-modulated structures and oxygen deficiencies around iron ions are also reflected in the observed spectra and variations in hyperfine parameters.

In this paper, we check and scan the (3+1)-dimensional variable-coefficient nonlinear wave equation which is considered in soliton theory and generated by considering the Hirota bilinear operators. We retrieve some novel exact analytical solutions, including cross-kink soliton solutions, breather wave solutions, interaction between stripe and periodic, multi-wave solutions, periodic wave solutions and solitary wave solutions for the (3+1)-dimensional variable-coefficient nonlinear wave equation in liquid with gas bubbles by Maple symbolic computations. The required conditions of the analyticity and positivity of the solutions can be easily achieved by taking special choices of the involved parameters. The main ingredients for this scheme are to recover the Hirota bilinear forms and their generalized equivalences. Lastly, the graphical simulations of the exact solutions are depicted.