International Journal of Modern Physics B

The gelation of waxy crude oil multiphase system can result in the formation of network cementitious structure, which seriously impacts the safe and economic production of crude oil. This paper reviews current experimental, theoretical and numerical results on the gelation of wax in crude oil. For the experimental side, the most important problems are in situ measurement and measurement accuracy. On the theoretical side, the present methods own defects of low accuracy and limited application scope. Numerically, the models are of oversimplification, which are hardly applied to the real production. Besides, as a promising solution, the research progress of crude oil pour point depressant is also reviewed. The molecular design is a powerful approach to develop the optimized pour point depressant. The goals of this paper are to bridge the microscale atomic interactions and the macroscale physicochemical properties of waxy crude oil and pour point depressant, so as to lay a solid theoretical basis for preventing and controlling wax deposition in crude oil. These are beneficial to the future efficient, clean and safe energy production system.

The effects of Al–Mg wire replacing Al–Cu wire on the microstructure, microhardness and tensile properties of 2219 aluminum alloy tungsten inert gas (TIG)-welded joints were studied. Comparing joints with Al–Cu wire, the capping welds of joints with Al–Mg wire can be strengthened by the introduction of Mg-containing strengthening phase and the hardness can be significantly improved. However, for joints with Al–Mg wire, both the solidification cracks caused by inappropriate control of alloying element content and the continuous brittle phases at grain boundaries around the weld zone (WZ) can result in the reduced tensile properties. The crack-free weld can be obtained by adjusting the alloying system of WZ. Furthermore, the geometry of WZ also affected the tensile properties of joints with Al–Mg wire.

We show that the Darboux transformation in “Infinite number of conservation laws and Darboux transformations for a 6-field integrable lattice system” [Int. J. Mod. Phys. B 33 (2019) 1950147] is incorrect, and construct a correct Darboux transformation.

In this study, the microstructure, the shear strength and Vickers-hardness of TA1/Q235B clad plates under different first pass rolling reduction ratio (FP3R) were investigated. The microstructure and bonding interface were analyzed by optical microscopy (OM), scanning electron microscopy (SEM). The Vickers-hardness and tensile shear strength were also detected. The result indicated a good bonding along the interface of the bonded with flat and smooth under different reduction ratio. The shear strength of the TA1/Q235B clad plate increases with the increase of reduction ratio which was 189 MPa at maximum. The maximum Vickers-hardness was approximately 198.7 HV. The thickness of Ti and Fe diffusion layer increases from 2.6 to 3.65 $\mu$m and 2.1 to 3.3 $\mu$m, respectively. TiC and Fe-Ti intermetallic compounds were formed at the bonding interface due to diffusion of Fe, Ti and C, causing micro-indentation at the interface to initiate cracking and diffusion, and reduced the bonding quality.

This investigation aims to present the thermally developed bioconvection flow of Williamson nanoliquid over an inclined stretching cylinder in presence of linear mixed convection and nonuniform heat source/sink. The activation energy and suspension of gyrotactic microorganisms are accounted with applications of bioconvection phenomenon. Appropriate nondimensional variables are opted to attain the dimensionless form of flow equations. The resulting momentum, energy, concentration and motile density equations are abridged to highly coupled and nonlinear in nature. The numerical treatment is followed for the solution procedure by employing the shooting method. The influence of some relevant dimensionless parameters is discoursed graphically along with physical justifications. Moreover, the impact of several dimensionless parameters on skin friction and Nusselt number is obtained and listed in tables. It is observed that the velocity of fluid shows a decreasing variation for Williamson fluid parameter. The change in unsteadiness parameter and heat source parameter enhanced the nanofluid temperature. The motile microorganisms profile declines with bioconvection constant and bio-convection Lewis number.

We theoretically investigate the effect of the nonmagnetic and magnetic impurities to the 2D parabolic Dirac system. The induced charge density by the charged impurity is obtained by the linear response theory within the random phase approximation. We also calculate in-detail, the Ruderman–Kittel–Kasuya–Yosida (RKKY) interaction between two magnetic impurities placed within the 2D sheet of the Dirac materials with isotropic and anisotropic dispersion. For the anisotropic dispersion, the RKKY interaction is also anisotropic and related to the lattice parameters which can be obtained through the DFT calculation or the experiments. The features of the RKKY interaction also can be treated as a signature of the topological phase transition as well as the change of Berry curvature. Our results are also illuminating to the study of the static screening and the RKKY interaction of the isotropic or anisotropic 3D Dirac/Weyl semimetals or the 2D transition metal dichalcogenide family.

Ga${}_X$In${}_{1-X}$As/Ga${}_Y$In${}_{1-Y}$Sb vertical heterojunctionless tunneling field effect transistor (VHJL-TFET) has been suggested to optimize the digital benchmarking parameters. In the proposed VHJL-TFET with type II heterostructure (i.e., $X=0.8$ and $Y=0.85$), slight changes in gate voltage cause switching from OFF-state to ON-state. As a result, the electrical properties of Ga${}_{0.8}$In${}_{0.2}$As/Ga${}_{0.85}$In${}_{0.15}$Sb VHJL-TFET are excellent in the sub-threshold region. The heterostructure with III–V semiconductors in the source-channel region increases the ON-state current ($I_{\mathrm{\text{ON}}}$) of the VHJL-TFET. Comparing the results of Ga${}_{0.8}$In${}_{0.2}$As/Ga${}_{0.85}$In${}_{0.15}$Sb VHJL-TFET with the simulated devices with type I heterostructure (i.e., $X=0.9$ and $Y=0.1$) and type III heterostructure (i.e., $X=0.1$ and $Y=0.4$) shows the improvement by 26% and 15% in the average subthreshold slope (SS). Sensitivity analysis for VHJL-TFET with the type II heterostructure shows that the sensitivity of OFF-state current ($I_{\mathrm{\text{OFF}}})$ to the body thickness ($T_b)$ and doping concentration ($N_D)$ is more than the sensitivity of the other main electrical parameters. The Ga${}_{0.8}$In${}_{0.2}$As/Ga${}_{0.85}$In${}_{0.15}$Sb VHJL-TFET with a channel length of 20 nm, $T_b=5$ nm, and $N_D=1\times 10^{18}$ cm${}^{-3}$ showed the $\mathrm{\text{SS}}=4.4$ mV/dec, $I_{\mathrm{\text{ON}}}$/$I_{\mathrm{\text{OFF}}}=\mathrm{\text{4E14}}$, and $I_{\mathrm{\text{ON}}}=8$ mA/um. As a result, Ga${}_{0.8}$In${}_{0.2}$As/Ga${}_{0.85}$In${}_{0.15}$Sb VHJL-TFET can be a reasonable choice for digital applications.

A modified Diffusion Limited Aggregation (DLA) model has been established for single and multi-center fractal growth. Number of particles $N$, size of one step $N_S$, deposition probability $p$, growth direction, and interaction effect are had been take into consideration for fractal analysis. In addition, the effect of internal interaction in multi-center growth have been taken into consideration. Fractal growth morphology shows strong boundary and interaction effects.

In this work, we investigate a new Kudryashov method (NKM) to find the exact and some new solutions of four different types of nonlinear Atangana conformable Boussinesq-like equations (NLACBEs). This is an appropriate algorithm for finding the exact solutions and also working for different types of nonlinear confirmable differential equations. In coastal and ocean engineering, some physical phenomenon is based on the exact solutions of the NLACBEs.

A systematic theoretical investigation of structural and energetic behaviors of 55-atom Pt–Ag–Au ternary nanoalloys has been performed in two different composition systems. We have performed Gupta and Density Functional Theory (DFT) approaches on chosen systems. The Basin-Hopping algorithm is used for structural optimizations of Pt_nAg${}_{13-n}$Au${}_{42}$ ($n=0$–13) and Pt_nAu${}_{13-n}$Ag${}_{42}$ ($n=0$–13) ternary nanoalloys with Gupta many-body potential to model interatomic interactions. Local optimization results show that while the tendency of Au atoms to be located varies according to the composition system, the tendency of Pt and Ag atoms to be located does not change in both. For all compositions of Pt–Ag–Au nanoalloys, the structures with the best chemical ordering were then reoptimized by DFT relaxations and the mixing energies of the Gupta and DFT levels were compared. Our mixing energy analysis showed that Pt_nAg${}_{13-n}$Au${}_{42}$ ($n=0$–13) nanoalloys are not energetically suitable for mixing at both Gupta and DFT level. Also, mixing energy variations of Pt_nAu${}_{13-n}$Ag${}_{42}$ ($n=0$–13) nanoalloys obtained at Gupta level does not agree with the one obtained at DFT level. In addition, it has been found that the minimization energy changes when an atom in the central site is exchanging by an atom in the second shell and surface.