Modern Physics Letters B

Under investigation in this paper is the (2+1)-dimensional coupled nonlinear Schrödinger (NLS) system with variable coefficients, which describes the propagation of an optical beam inside the two-dimensional graded-index waveguide amplifier with the polarization effects. Through a similarity transformation, we convert that system into a set of the integrable defocusing (1+1)-dimensional coupled NLS equations, and subsequently construct the bright–dark soliton solutions for the original system which are converted from the ones of the latter set. With the graphic analysis, we discuss the soliton propagation and collision with r(t), which is related to the nonlinear, profile and gain/loss coefficients. When r(t) is a constant, one soliton propagates with the amplitude, width and velocity unvaried, while velocity and width of the one soliton can be affected, and two solitons possess the elastic collision; When r(t) is a linear function, velocity and width of the one soliton varies with t increasing, and collision of the two solitons is altered. Besides, bound-state solitons are seen.

We propose a novel metal–insulator–metal (MIM) waveguide structure consisting of a stub and a double side-coupled nanodisk. Its electromagnetically-induced transparency (EIT)-like response and transmission properties are numerically investigated by the finite element method (FEM). Numerical simulation results show that the EIT-like phenomenon appears in the transmission spectra. The transparency window can not only be manipulated by changing the radius of the nanodisk and the height of the stub, but also appear redshifted with the increasing of the refractive index n. Furthermore, the MIM waveguide structure is easy to yield a high sensitivity of 1200 nm/RIU with a figure of merit about $2.2\times 10^4$, which may be applied to nanosensors. These results would help us design the high-performance plasmonic devices based on the EIT-like response.

Based on the technique of quantum teleportation, a new multi-party quantum key agreement protocol is proposed. In this protocol, all users first share EPR pairs via public quantum channels. Afterwards, the states of signal particles can be transferred between two adjacent users by quantum teleportation. With the help of four unitary encoding operations, all users can encode their separate secret key into the traveling quantum states. In the end, all users can derive the final shared key synchronously. The security analysis shows that the presented protocol is secure against some common attacks and completely loss tolerant.

In this study, a new car-following model is established aiming to predict the variation of vehicle headways on urban road. The linear stability condition is derived corresponding to the prevision of headway in moving. The modified Korteweg–de Vries (mKdV) equation is deduced through the nonlinear analysis. The kink–antikink soliton solution of the mKdV equation can interpret the urban traffic jams near the critical point under the prevision of vehicle headway. Moreover, it is clear that the prevision of headway effect did improve the stability of urban traffic flow since the traffic jams are alleviated efficiently by taking into account the prevision of headway term in numerical simulations, which are consistent with the theoretical analysis.

Based on the characteristics of secondary electron emission and the relationships among parameters of secondary electron yield $\delta$ in the low-energy range of $E_{p0}\leqq E_{p0m}\leqq 800$ eV (low-energy $\delta$), the universal formula for low-energy $\delta$ as a function of $E_{p0}$, $E_{p0m}$ and maximum $\delta ({\delta }_m)$ was deduced, where $E_{p0}$ and $E_{p0m}$ are the incident energies of primary electron and of ${\delta }_m$, respectively. From the deduced universal formula and experimental low-energy $\delta$ from metals, semiconductors and insulators, special formula for low-energy $\delta$ from metals as a function of $E_{p0}$, $E_{p0m}$ and ${\delta }_m$ and that for low-energy $\delta$ from semiconductors and insulators as a function of $E_{p0}$, $E_{p0m}$ and ${\delta }_m$ were deduced, respectively. The results were analyzed, it can be concluded that the two deduced special formulae can be used to calculate low-energy $\delta$ from metals, semiconductors and insulators, respectively.

In this contribution, the effects of two key internal parameters, i.e. the linewidth-enhancement factor $(\alpha )$ and gain nonlinearity $(𝜀)$, on time-delay signatures (TDS) concealment of two mutually-coupled semiconductor lasers (MCSLs) are numerically investigated. In particular, the influences of $\alpha$ and $𝜀$ on the TDS concealment are compared and discussed systematically by setting different values of frequency detuning $(\mathrm{\Delta }f)$ and injection strength $(\eta )$. The results show that the TDS can be better suppressed with high $\alpha$ or lower $𝜀$ in the MCSLs. Two sets of desired optical chaos with TDS being strongly suppressed can be generated simultaneously in a wide injection parameter plane provided that $\alpha$ and $𝜀$ are properly chosen, indicating that optimizing TDS suppression through controlling internal parameters can be generalized to any delayed-coupled laser systems.

We study the quantum Fisher information (QFI) of a one-dimensional anisotropic XY chain in a transverse field with three-spin interaction. It is shown that the QFI, computed at a finite temperature, can be used to estimate the critical point (CP) of the quantum phase transition (QPT) at zero temperature. The accuracy of the obtained result depends on both the anisotropy parameter of the chain and the local observable used in the computation of QFI.

The process of conversion from $\beta$-Ga₂O₃ single crystal to gallium nitride (GaN) in an atmosphere of NH₃ by chemical vapor deposition is investigated. The surface morphology and microstructure of the GaN nanoparticles are observed by scanning electron microscope, which indicates that the growth of GaN is via the Volmer–Weber mechanism. The $\beta$-Ga₂O₃ is firstly evaporated at high temperature to form the porous layer, followed by the surface-defect induced GaN nucleation formation. The crystalline structure and epitaxial relationship of the GaN nanoparticles are investigated by X-ray diffraction (XRD) via $\omega$–$2𝜃$, showing GaN (0002) and (0004) diffraction peaks in the XRD spectra. It is concluded that the polycrystalline GaN film with hexagonal structure has a strong c-axis preferential orientation.

Bubble is the heart of the microfluidic chip, which takes a significant role in drug release, biological detection and so on. In this case, bubble flow characteristics in microfluidic chip are the key to realize its function. In this paper, bubble flow characteristics in the microfluidic chip have been studied with high speed photography system by controlling the wettability and the heat flux of the microelectrode surface. The result shows that bubble flows faster on the electrode with hydrophobic surface. In addition, loading current to the electrode with hydrophilic surface could also speed up the movement of bubble, and the flow rate of bubble increases with the increasing heat flux of the electrode.

In this paper, we proposed two reduced quantities, based on which we found that the curves of surface tension versus temperature of different saturated fluids can collapse into a single curve. Then a corresponding state-based correlation is proposed and then checked for 66 saturated fluids including simple fluids such as argon, nitrogen, etc., and some refrigerants in the temperature range from the triple point temperature to 0.992 times the critical temperature. By comparing with NIST data, the proposed correlation reproduces NIST data with AAD $<$ 1% for 21 fluids, AAD $<$ 2% for 26 fluids, and AAD $<$ 5% for 46 fluids.

We consider the pressure and correlation functions of d-dimensional classical continuous models of Kac type. We prove that if the kth moments of the potential exist, then the system cannot have phase transitions of order lower than k. We also obtain a better formula for the higher derivatives of the pressure that leads to more precise estimates of the truncated correlations.

As one of the most common mesoscale structures in real-life networks, k-core hierarchical structure has attracted a lot of attention. Recent research about k-core always focuses on detecting influential nodes determining failure or epidemic propagation. However, few studies have attempted to understand how k-core structural properties can affect dynamic characteristics of network. In this paper, the influences of depth and coupling preferences of k-core on the cascading failures of interdependent scale-free networks are investigated. First, k-core structures of some real-life networks are analyzed, and a scale-free network evolution model with rich and successive k-core layers is proposed. Then, based on a load-based cascading model, the influence of the depth of k-core is investigated with a new evaluation index. In the end, two coupling preferences are analyzed, i.e. random coupling (RC) and assortative coupling (AC). Results show that the lower the depth is, the more robust the interdependent networks will be, and we find AC and RC perform dissimilarly when the capacity varies. Furthermore, all the effects will be affected by the initial load.