Modern Physics Letters B

It was theoretically predicted more than 20 years ago [A. G. Lebed and K. Yamaji, Phys. Rev. Lett. 80, 2697 (1998)], that a triplet quasi-two-dimensional (Q2D) superconductor could restore its superconducting state in parallel magnetic fields, which are higher than its upper critical magnetic field, $H>H_{c2}(0)$. It is very likely that, recently, such phenomenon has been experimentally discovered in the Q2D superconductor UTe₂ by Nicholas Butch, Sheng Ran, and their colleagues and has been confirmed by Japanese–French team. We review our previous theoretical results using such a general method that it describes the reentrant superconductivity in the abovementioned compound and will hopefully describes the similar phenomena, which can be discovered in other Q2D superconductors.

By performing density functional theory (DFT) calculations, we demonstrate that periodically repeating heterostructures of zigzag borophene nanoribbons (BNR) of different widths can form stable borophene superlattice (BSL). The energy band structures of BSL can be modulated through modifying the width and length of the segments. A metal-semiconductor transition can be obtained when the length of each segment is lengthened, whereas, the magnetism of BSL is influenced by the width of the segments. In those magnetic systems, the magnetic moments are mainly localized on protruding B atoms located at the edge, while no magnetic moments occur in the center B atoms. The hydrogenated BNR and BSL are further investigated. The hydrogenation can modify the electronic properties of BNR and BSL as well as quench the magnetism. All hydrogenated BNR and BSL are non-magnetic. Our results indicate that great potential exists in these systems for borophene utilization in nanoelectronics and spintronics.

The electronic and optical properties of the adsorption of alkali metals (Li, Na, K, Rb, Cs) on graphitic carbon nitride (g-C₃N${}_4)$ were calculated and studied based on the first principles of density functional theory. The results investigate that alkali metals adsorbed g-C₃N₄ has metallic properties, while intrinsic g-C₃N₄ was semiconducting. Importantly, the charge density differential investigated the charge transfer discovered between the alkali metal and the g-C₃N₄ monolayer. Meanwhile, the charges (electrons) transfer from the alkali metals to the g-C₃N₄ system leading to the increase of most carriers in the g-C₃N₄ system, reducing the resistance of sensors, which is conducive to sensor detection applications. The work function of g-C₃N₄ decreased from 4.82 eV to 4.09 eV. Especially, the work function of Cs-adsorbed g-C₃N₄ is the lowest at 4.09 eV, and the reduction rate is 15.15 %, indicating it easier to emit electrons from an external electric field. Moreover, the absorption spectrum of the alkali metal adsorbed on g-C₃N₄ in the visible light range shows absorption peaks at 380 nm, 412 nm, 420 nm and 476 nm, which cover the visible light area. Thus, the alkali metals adsorbed g-C₃N₄ system can be used for visible light catalytic. Adsorption of alkali metals can expand the application of g-C₃N₄ in optoelectronic devices.

Wave function of the Bose–Einstein condensate satisfies the nonlinear evolution equation set, which is composed of the driven-dissipative Gross–Pitaevskii equations and rate equation (GPR). In this paper, a three coupled GPR equation is studied. By virtue of the bilinear method, multi-soliton solutions of this GPR equation are attained. Propagation and interaction of the solitons are discussed: propagation direction of the solitons are determined by the wave number; repellent and attractive two solitons are obtained by virtue of adjustment the wave numbers; interaction of the two solitons bound state are discussed; three solitons bound state are attained.

In this work, one of the important models in nonlinear wave theory and also in nonlinear acoustic, the Lin–Reissner–Tsien (LRT) equation is considered. For the homogeneous form of LRT equation, the exact solutions are obtained. For steady and non-steady state forms of the LRT equation with force terms, similarity reductions are obtained via the classical symmetry analysis method. Both of the considered problems are not seen in the literature. The results obtained in this paper are new solutions and believed to have a major role in the development of the model.

Spar Drilling Production Storage and Offloading (SDPSO) is a new type of deep ocean platform developed in recent years. The process of oil-water displacement is used for oil storage and offloading and the research on the accompanying heat flow has been significant. The wax precipitation and solidification at low temperature will particularly affect the flowing of oil in the displacement process. When the heat flow is concerned, numerical simulation requires large computation. It is necessary to develop an efficient numerical method for this calculation. As a kind of interface tracking method, the volume of fluid (VOF) method needs less computing resources compared with other multiphase numerical methods. As for thermal expressions, there are mainly two kinds of governing equations, i.e. temperature equation and enthalpy equation, and two kinds of interpolation scheme of heat conductivity, i.e. algebraic interpolation scheme and harmonic interpolation scheme. There is a need to find out which combination of governing equation and interpolation scheme of heat conductivity would result in a better precision for the heat flow. Therefore, four non-isothermal solvers, corresponding to the four combinations, are established. After comparison with an analytical solution, it is found that the temperature equation together with the harmonic interpolation scheme of heat conductivity results in better precision.

At present, drivers can rely on road communication technology to obtain the current traffic status information, and the development of intelligent transportation makes self-driving possible. In this paper, considering the mixed traffic flow with self-driving vehicles and the taillight effect, a new macro-two-lane lattice model is established. Combined with the concept of critical density, the judgment conditions for vehicles to take braking measures are given. Based on the linear analysis, the stability conditions of the new model are obtained, and the mKdV equation describing the evolution mechanism of density waves is derived through the nonlinear stability analysis. Finally, with the help of numerical simulation, the phase diagram and kink–anti-kink waveform of neutral stability conditions are obtained, and the effects of different parameters of the model on traffic flow stability are analyzed. The results show that the braking probability, the proportion of self-driving vehicles and the critical density have significant effects on the traffic flow stability. Considering taillight effect and increasing the mixing ratio of self-driving vehicles can effectively enhance the stability of traffic flow, but a larger critical density will destroy the stability of traffic flow.

To ensure the security of web applications and to reduce the constant risk of increasing cybercrime, basic security principles like integrity, confidentiality and availability should not be omitted. Even though Transport Layer Security/Secure Socket Layer (TLS/SSL) authentication protocols are developed to shield websites from intruders, these protocols also have their fair share of problems. Incorrect authentication process of websites can give birth to notorious attack like Man in The Middle attack, which is widespread in HTTPS websites. In MITM attack, the violator basically positions himself in a communication channel between user and website either to eavesdrop or impersonate the communicating party to achieve malicious goals. Initially, the MITM attack is defined as a binary machine learning problem. Deep Q learning is utilized to build the MITM attack classification model. Thereafter, training process is applied on 60% of the obtained dataset. Remaining 40% dataset is used for testing purpose. The experimental results indicate that the proposed technique performs significantly better than the existing machine learning technique-based MITM prediction techniques for SSL/TLS-based websites.

In order to explore new ways to detect and remove heavy metal ions from industrial wastewater, the first-principles method based on density functional theory has been used to investigate the performance of carbon nanotubes (CNTs) in adsorbing divalent heavy metal ions which include Zn${}^{2+}$, Cu${}^{2+}$, Pb${}^{2+}$ and Sn${}^{2+}$. Results show that the adsorption of Zn${}^{2+}$ on CNTs is weak and only physical adsorption forms between them. However, for Cu${}^{2+}$, Pb${}^{2+}$ and Sn${}^{2+}$, the final adsorption distance with CNTs is greatly decreased, and the adsorption energy and charge transfer amount with CNTs are significantly increased. In addition, the charge density of Cu${}^{2+}$, Pb${}^{2+}$ and Sn${}^{2+}$ overlaps effectively with that of CNTs. These indicate the formation of strong chemisorption between these ions and CNTs. Therefore, CNTs could be used as a sensing material to detect and remove Cu${}^{2+}$, Pb${}^{2+}$ and Sn${}^{2+}$ from wastewater. The research provides theoretical guidance for the application of CNTs in heavy metal ions treatment.

Silicon/glass anodic bonding is widely investigated during MEMS packaging of multi-stack structures. The electrical behavior of anode bonding can be described as the charging and discharging process of RC circuit. Here, we conduct the equivalent RC circuit model analysis and experimental investigation, and demonstrate that voltage division and electricity leakage are the dilemma for the conventional multi-stack anodic bonding. By using feedthrough, the feasibility and convenience of “shorting out bonding” is presented, which is exampled through the wafer-level packaging of the MEMS gyroscope. Result from the sensor’s vacuum characterization reveals that shorting out bonding for multi-stack silicon/glass structures is an effective method for wafer-level packaging due to long-term stability and low temperature property.‘

In this study, the drag force and heat flux reduction mechanism induced by the aerodisk (with disks on its nose) with the freestream Mach number being 4.937 has been numerically investigated, and the simulations have been carried out by the three-dimensional Reynolds-averaged Navier–Stokes equations coupled with the SST $k-\omega$ turbulence model. The influence of the angle of attack on the drag and heat flux reduction has been analyzed comprehensively. The obtained results show that the drag force of the spiked blunt body can be reduced by the aerodisk, and the drag force decreases by 24.63%. The flow mechanism of the complex flow is drastically modified by the angle of attack, and this results in a strong flow asymmetry. This asymmetry becomes more and more obvious as the angle of attack increases. Both the pressure force and viscous force increase with the increase of the angle of attack. Moreover, both the lift and drag coefficients increase as the angle of attack increases, and the lift-to-drag ratio increases first and then decreases with the increase of the angle of attack. When the angle of attack is $6^{\circ }$, the maximum lift-to-drag ratio is close to 0.36.

Binary Bell polynomial approach is applied to study the coupled Ramani equation, which is the generalization of the Ramani equation. Based on the concept of scale invariance, the coupled Ramani equation is written in terms of binary Bell polynomials of two dimensionless field variables, which leads to the bilinear coupled Ramani equation directly. As a consequence, the bilinear Bäcklund transformation, Lax pair and conservation laws are systematically constructed by virtue of binary Bell polynomials.

An insight into electronic structure and optical feature of S-adsorbed 3C–SiC (111) surface is carried out employing first-principles calculation. It is found that the ${\mathrm{\text{T}}}_{\mathrm{\text{o}}}$ and B position systems with adsorption energies of 3.880 and 3.895, respectively, are relatively stable compared to the ${\mathrm{\text{T}}}_{\mathrm{\text{w}}}$ and C systems. Impurity energy levels are present near Fermi level in C and ${\mathrm{\text{T}}}_{\mathrm{\text{w}}}$ position adsorption systems and the band-gap decreases obviously in the two systems. A raindrop-like electron cloud of S atom can be observed in ${\mathrm{\text{T}}}_{\mathrm{\text{w}}}$ adsorption system and the order of the chemical bond strength in the adsorption system is $(\mathrm{\text{B}},{\mathrm{\text{T}}}_{\mathrm{\text{o}}})>{\mathrm{\text{T}}}_{\mathrm{\text{w}}}>\mathrm{\text{C}}$. The B and ${\mathrm{\text{T}}}_{\mathrm{\text{o}}}$ adsorption systems have good light permeability in the visible and infrared regions, while the C and ${\mathrm{\text{T}}}_{\mathrm{\text{w}}}$ adsorption systems are relatively suitable as dielectric materials and have high service life when they as devices in the ultraviolet region.

As a key point of the stealth performance, acoustic characteristics of a screw mixed water-jet pump were investigated under the quasi-submerged state. The relationships between thrust and rotation speed of screw-mixed pump, drag, and submerged velocity of water-jet propulsion were obtained from the flume tests and numerical simulation. Based on the results of the unsteady flow field calculation with the detached eddy simulation (DES), the sound radiation fields of the screw mixed water-jet propulsion at different rotation speeds were investigated by the finite element method (FEM) coupled with the vibro-acoustic method. The flow-induced dipole source noise of every flow passage component increases with the increasing of rotation speed. The mathematical relations of the flow-induced noise at impeller between different rotation speeds were established. The maximum sound pressure level (SPL) of every flow passage component appears at the impeller blade-passing frequency (BPF). In the medium-high frequency domain, dipole source induced noise from the impeller is the main external noise field during the propulsion process. At the first-order BPF, the ratio of SPL of the impeller is equal to the 0.5 power of the rotation speed in the phase of $0^{\circ }$, $90^{\circ }$, $180^{\circ }$, and $270^{\circ }$. At the sixth-order BPF, the ratio of SPL of the impeller is directly proportional to the reciprocal power of rotation speed ratio in the phase of $0^{\circ }$, $90^{\circ }$, $180^{\circ }$, and $270^{\circ }$.