Modern Physics Letters B

In this paper, an alternative approach of spectral meshless radial point interpolation (SMRPI) is applied to the modified anomalous fractional sub-diffusion equation with a nonlinear source term in one and two dimensions. The time fractional derivative is described in the Riemann–Liouville sense. The applied approach is based on a combination of meshless methods and the spectral collocation techniques. The point interpolation method with the help of radial basis functions is used to construct the shape functions which act as basis functions in the frame of the SMRPI. It is proved that the scheme is unconditionally stable with respect to the time variable in $H^1$ and convergent with the order of convergence ${𝒪}(\delta t^{1+\gamma })$, $0<\gamma <1$. In this work, the thin plate splines (TPS) are used as the radial basis functions. In order to eliminate the nonlinearity, a simple predictor–corrector (P–C) scheme is used. The results of numerical experiments are compared to the analytical solutions in order to confirm the accuracy and the efficiency of the presented scheme.

Under investigation in this paper are the N-coupled complex short pulse (N-CSP) equations, which describe the propagation of simultaneous N ultrashort pulses in a nonlinear fiber medium. Through the Hirota method, the m-bright-n-dark $(m+n=N)$ soliton solutions are obtained. Elastic and inelastic interactions between the mixed-type solitons are derived through the asymptotic analysis. As an example, the oblique interactions and the bound states of the 2-bright-1-dark and 1-bright-2-dark solitons for 3-CSP equations are analyzed graphically. Finally, the condition of the modulation instability of the plane-wave solutions for 2-CSP equations is given through the linear stability analysis.

In order to improve the comprehensive effect of Urban Traffic Control System (UTCS) and Urban Traffic Flow Guidance System (UTFGS), this paper puts forward a collaboration optimization model of dynamic traffic control and guidance based on Internet of Vehicles (IOV). With consideration of dynamic constraints of UTCS and UTFGS, UTCS is taken as the fast variable, and UTFGS is taken as the slow variable in the collaboration optimization modeling. The conception of Variable Cycle Management (VCM) is presented to solve the mathematical modeling problem under the background of the two variables. A unified framework for VCM is proposed based on IOV. The delay and travel time are calculated based on lane-group-based cell transmission model (LGCTM). The collaboration optimization problem is abstracted into a tri-level programming model. The upper level model is a cycle length optimization model based on multi-objective programming. The middle level model is a dynamic signal control decision model based on fairness analysis. The lower level model is a user equilibrium model based on average travel time. A Heuristic Iterative Optimization Algorithm (HIOA) is set up to solve the tri-level programming model. The upper level model is solved by Non-dominated Sorting Genetic Algorithm II (NSGA II), the middle level model and the lower level model are solved by Method of Successive Averages (MSA). A case study shows the efficiency and applicability of the proposed model and algorithm.

Using N-acetyl-L-cysteine (NAC) as capping agent and different amounts of hydrazine hydrate as growth promoter, in this paper, we report a simple way for preparation of aqueous-based ZnS nanocrystals (NCs). The small-sized and well-dispersed NCs with cubic zinc blende structure and size-dependent optical behavior have been characterized by XRD, TEM, FT-IR, UV-Vis, and photoluminescence (PL) measurements. Disappearance of the thiol-related peak in the FT-IR spectrum of NAC-capped ZnS NCs demonstrated the well-passivation of ZnS NCs by deprotonated NAC molecules. Variation of optical properties of ZnS NCs has been studied at different hydrazine amounts and refluxing times. The growth-assisting characteristic of hydrazine hydrate was demonstrated by redshift in absorption edge as the hydrazine amount increased from 5 to 20 mmol, and ensuing decrease in band gap energy of ZnS NCs from 4.47 eV to 4.0 eV. On the other hand, increasing the refluxing time duration up to 20 h, resulted in obvious redshift in absorption edge and subsequent decrease in the band gap energy from 4.56 eV to 3.85 eV. The optical estimation on the size of the as-prepared ZnS NCs was obtained through effective mass approximation. Results indicated that all the NCs are small enough near the excitonic Bohr radius of ZnS which revealed the presence of strong quantum confinement effects. Effect of these parameters on PL emission intensity of ZnS NCs was studied and it was observed that the best emission result is at the presence of 12.5 mmol hydrazine hydrate and during 16 h heating. Finally, analyzing chemical stability of the as-prepared ZnS NCs against H₂O₂ corrosion demonstrated a well-accepting stability of emission intensity even after 108 min.

This study investigates the optical properties of samarium-doped microstructured and nanostructured CaO–CeO₂ mixed solutions. Conventional solid state method and auto-igniting combustion synthesis were used for the preparation of the samples. The as-prepared samples were characterized using X-ray diffraction, Fourier Transform Infrared spectroscopy, Transmission Electron Microscopy, UV-Visible spectroscopy and photoluminescence spectroscopy. A mixed phase formation with phases of CaO, CeO₂ and Ca(OH)₂ was observed form X-ray diffraction studies. The transmission electron microscopic studies have shown that the average particle size of the as-prepared powder was in the range of 30–40 nm. A blueshift is observed in the bandgap of the nanocrystalline samples. Strong orange–red emission was observed for Sm${}^{3+}$-doped samples and the chromaticity values were calculated using CIE chromaticity diagram.

Semi-quantum secret sharing (SQSS) can transmit secret messages. Most existing SQSS protocols can only use one or two specific entangled states to share unspecific or specific classical message. In this paper, we propose a novel SQSS protocol using N different unspecific two-particle entangled state $|\phi {〉}_i=x_i(|++〉+|--〉)+y_i(|++〉-|--〉)$, $(x_i^2+y_i^2=1/2)$ to share unspecific message, in which quantum Alice can transmit classical messages with classical Bob and Charlie. In addition, we have proved that the protocol can strongly resist some forms of eavesdropping.

The deposition kinetics and microstructure of chemical vapor deposition (CVD) of Nb on the Mo substrate at different deposition variables is investigated. The morphology of CVD Nb is columnar, it exhibits a strong preferred orientation and its growth direction is perpendicular to the substrate surface, the deposition rate and grain size increased with the increase of deposition temperature. The deposition rate conforms to the Arrhenius formula, the activation energy $(\mathrm{\Delta }Q)$ at high temperature and low temperature is 0.85 kJ/mol and 7.2 kJ/mol, respectively. The rate-limiting step for CVD Nb at high temperature is chemical reaction step, whereas that is the mass transport step at low temperature. Chlorination temperature has a weak influence on deposition rate and grain structure, the deposition rate and grain size of CVD Nb increased with the increase of the chlorine flow and hydrogen flow, the maximum deposition rate is $13.3\mathrm{\text{g}}\cdot {\mathrm{\text{h}}}^{-1}$, thus, the optimum deposition temperature is 1200${}^{\circ }$C, chlorination temperature is 350${}^{\circ }$C, hydrogen flow is 400 ml, chlorine flow is 200 ml.

Breaking Lorentz reciprocity is one necessary condition of optical isolator design. Unidirectional wavelength-mode conversion will be realized in a time-dependent system through a short operating range. Based on plasma dispersion effect, generate space-asymmetric periodical time-space modulation on silicon waveguide, and non-reciprocal propagation is realized in the waveguide. The designed unidirectional wavelength-mode conversion waveguide demonstrated that in the forward direction, input 1.55 $\mu$m fundamental mode light signal and then output 1.5492 $\mu$m is of 1st-order mode, while in the backward direction, input 1.5492 $\mu$m is of 1st-order mode light signal and then output 1.5484 $\mu$m is of fundamental mode. Based on this non-reciprocal structure, mode conversion waveguide and two-ring resonance filters were designed then, to accomplish on-chip optical isolation. The scale of the designed isolator is 160 $\mu$m × 60 $\mu$m, and the isolation is 21 dB, revealing perfect application potential.

In this paper, the stochastic resonance (SR) phenomenon in a time-delayed tumor cell growth system subjected to a multiplicative periodic signal, the multiplicative and additive noise is investigated. By applying the small time-delay method and two-state theory, the expressions of the mean first-passage time (MFPT) and signal-to-noise ratio (SNR) are obtained, then, the impacts of time delay, noise intensities and system parameters on the MFPT and SNR are discussed. Simulation results show that the multiplicative and additive noise always weaken the SR effect; while time delay plays a key role in motivating the SR phenomenon when noise intensities take a small value, it will restrain SR phenomenon when noise intensities take a large value; the cycle radiation amplitude always plays a positive role in stimulating the SR phenomenon, while, system parameters play different roles in motivating or suppressing SR under the different conditions of noise intensities.

This paper constructs a new 4D chaotic system from the Sprott B system. The system is dissipative, chaotic with two saddle foci. The bifurcation diagrams verify that the system exists multiple attractors with different initial values, including two strange attractors, two periodic attractors. Furthermore, we apply the passive control to control the system. A controller is designed for driving the system to the origin. The simulations show our theoretical results visually.

Propagation of the electromagnetic wave through a system with complex permittivity is investigated. The system consists of two media, one is passive and surrounds the two barrier slabs made out of the second material with complex dielectric constant. Expression for transmission probability is obtained along with equation which allows calculation of the resonant frequency. Analytical expressions for reflection and absorption probabilities are acquired as well. It will be shown, if the frequency is given, that the transmission probability (along with reflection and absorption probabilities) approaches infinity for one particular value of the dielectric constant with negative imaginary part, which is used to describe active media. Furthermore, conditions for appearance of these transmission singularities are obtained.

An important stage in speech enhancement is to estimate noise signal which is a difficult task in non-stationary and low signal-to-noise conditions. This paper presents an iterative speech enhancement approach which requires no prior knowledge of noise and is based on low-rank sparse matrix decomposition using Gammatone filterbank and convex distortion measure. To estimate noise and speech, the noisy speech is decomposed into low-rank noise and sparse-speech parts by enforcing sparsity regularization. The exact distribution of noise signals and noise estimator is not required in this approach. The experimental results demonstrate that our approach outperforms competing methods and yields better overall speech quality and intelligibility. Moreover, composite objective measure reinforced a better performance in terms of residual noise and speech distortion in adverse noisy conditions. The time-varying spectral analysis validates significant reduction of the background noise.

In this paper, high-power pulse-pumped erbium–ytterbium co-doped fiber amplifiers (EYDFAs) for simultaneous amplification of low-repetition rate pulses in the 1.0 $\mu$m and 1.5 $\mu$m bands are numerically investigated. The influences of the peak power and pulse-width of the pump and time delay between the pump and signal pulses on the performance of the amplifier are systematically analyzed. The results show that a pulse-pumped EYDFA is capable of simultaneously amplifying dual-band pulses. The optimal pulse-width of the pump is mainly determined by the allowable power of the backward Yb amplified spontaneous emission (ASE). By simply adjusting the time delay between the pump and signal pulses, the power ratio of the dual-band signals can be easily changed. Such kind of dual-band-pulsed EYDFAs have great potential applications in fields such as the generation of visible or mid-infrared light by nonlinear frequency conversion, counter stealth Lidar, etc.

In this comment, we show that the efficiency of the proposed quantum dialogue scheme in the paper [Mod. Phys. Lett. B 29 (2015) 1550018] cannot reach 100%, but 66.7%.