International Journal of Modern Physics B

The terahertz absorption spectrum of the five aging explosive samples (PETN, RDX, HMX, LLM-105 and TATB) was measured and calculated by Terahertz time-domain spectroscopy system (THz-TDS) and air-biased coherent detection system (ZAP-ABCD), respectively. In this paper, compared with the unaging explosive, each aging explosive sample’s terahertz time-domain spectra were obtained and the terahertz absorption spectra were calculated by using Fourier transform and Lambert’s law. The results show that there are several terahertz absorption peaks which were called “fingerprint spectra” for different aging explosive samples in the range of 0.3–6.0 THz spectrum. Meanwhile, the results also show that the locations of the characteristic absorption peaks are not the same. Moreover, the unaging and aging explosive samples have obviously different terahertz absorption spectra.

Narrow bandwidth and specific incident angle are the main drawbacks in real-life applications for the existed carpet cloaking based on the acoustic metasurface (AM). Here, we tackle to get over the problems by proposing a reprogrammable AM. The unit cell is composed of water sink and filling nozzle. By incorporating an external water pumping system into each individual unit cell, the reflected phase can be readily regulated. Since the pumping process is reversible, the AM is reprogrammable under the control of the water pumping system in the frequency range of 3430–6860Hz. Both the acoustic cloaking and disguising are designed based on the proposed AM. The double security for the target object can be ensured to avoid being detected by combining the two designs. Simulated results with the finite element method indicate that the acoustic cloaking and disguising can work in the broad bandwidth of 66.7% of the central frequency with full-range incident angles from $-90^{\circ }$ to $90^{\circ }$. Our design shows promise for applications in realizing the practical skin cloaking and disguising one step closer.

In this paper, we propose two construction methods for binary and nonbinary quantum stabilizer codes based on symmetric matrices. In the first construction, we use the identity and symmetric matrices to generate parity-check matrices that satisfy the symplectic inner product (SIP) for the construction of quantum stabilizer codes. In the second construction, we modify the first construction to generate parity-check matrices based on the Calderbank–Shor–Stean structure for the construction of quantum stabilizer codes. The binary and nonbinary quantum stabilizer codes whose parameters achieve equality of the quantum singleton bound are investigated with the code lengths ranging from 4 to 12.

The ability of MoS₂ nanomaterials as adsorbent and photocatalytic materials of methylene blue (MB) dye after $\gamma$-ray irradiation is investigated. The MoS₂ nanomaterials are prepared by a simple hydrothermal route, and then irradiated with Co-60 gamma radioisotope at different doses of 1, 10, 100, 1000 kGy. All the samples are characterized by X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Fourier Transform Infrared Spectroscopy (FTIR), Diffusivity Reflectance Spectroscopy (DRS) and Brunauer–Emmet–Teller (BET). The XRD analysis shows no change in crystal structure of MoS₂ nanomaterials after irradiation. The DRS analysis indicates the optical bandgap increases from 1.73 to 1.82, 1.86, 1.94 and 2.00 eV, respectively. The performance of the dye-absorbing solutions and the photocatalytic dye solutions before and after irradiation is compared. After $\gamma$-ray irradiation, the adsorption capacity of the MoS₂ nanomaterials degrades, which can be attributed to the decreased specific surface area, from 77.060 to 48.812, 35.855, 38.789 and 27.137 m²/g, respectively. The photocatalytic degradation ability for the MB solution also decreases due to the increase of optical bandgap of the samples after $\gamma$-ray irradiation.

In this paper, a sensor structure operating in the microwave frequency band is used and it is aimed to determine whether fuel samples are branded or not. In the literature, the studies on the sensor applications of metamaterials (MTMs) have increased considerably in recent years. However, this study, unlike other studies, focuses on determining the changes in electromagnetic parameters of different fuel samples at X band frequencies. For this purpose, the electromagnetic properties of the branded and unbranded fuel samples are measured experimentally. Then, simulation studies are carried out using the experimental results and the dimensions of the resonators are optimized to determine the most suitable structure. Fabrication of MTM sensor structure is then performed using optimized dimensions. Finally, the experimental study is carried out using the sensor structure.

In this paper, our purpose is to construct multiwave solutions for the system of equations for the ion sound and Langmuir waves (SEISLWs) by utilizing the traveling wave and logarithmic transformation with the help of symbolic computation and the ansatz function method. We apply three distinctive approaches: namely, positive quadratic function approach, three waves approach and double exponential approach. By choosing suitable parametric values, 3D graphics are plotted to get different types of multiwave solutions including lump waves, rogue wave and multipeak soliton solutions. Moreover, we revealed very interesting multiwaves interactional phenomena.

In this work, we used the Floquet–Magnus expansion (FME) and the Fer expansion (FE) approaches to investigate the spin dynamics during the rotary-resonance recoupling (R³) radiation experiment in solid-state nuclear magnetic resonance (SSNMR). We reformulated the two approaches and calculated their respective effective Hamiltonians and propagators. We compared the two approaches and found that the FME is more appropriate to describe the spin dynamics in the R³ experiment compared to the FE. The equations governing the spin dynamics of the first three orders of the FME look similar to the equations of the FE. Nevertheless, the FME has two additional parameters making the approach more applicable to various situations. This clearly shows that the FME will be more practical for the modifications of the R³ pulse sequence with the major corrections coming from the terms that include the additional parameters, which are not available in the FE. This work is significant and contributes theoretically and numerically in the field of spin dynamics, magnetic resonance and in particular SSNMR.

In this paper, a computational fluid dynamics–discrete element method (CFD–DEM) coupling method is established to simulate the starch granule injection by coupling CFD and DEM. Then a gas–solid two-phase pulsed jet system is designed to capture the flow field trajectory of particle injection (colored starch with a mean diameter of 10.67 $\mu$m), and the image is processed by color moment and histogram. Finally, the simulation results are compared with the experimental results, and the following conclusions are drawn. The numerical simulation results show that with the increase of injection pressure, the injection height increases gradually. When the injection pressure reaches above 0.4 MPa, the increase of injection height decreases. The experimental images show that the larger the pressure (i.e., the greater the initial velocity), the faster the velocity of particle distribution in the space, and the injection heights with the injection pressures of 0.4 MPa and 0.5 MPa are close, which is consistent with the result from the FLUENT numerical simulation based on CFD–DEM.

In this paper, a novel method has been used to solve time fractional $(1+2)$-dimensional nonlinear Schrödinger equation with dual-power law nonlinearity. Using the newly-proposed Jacobi elliptic function expansion method, new double periodic, bright and soliton solutions of the aforesaid equation have been obtained. The results show that the proposed method is a convenient, efficient and straightforward technique to devise new soliton solutions of the presently-mentioned equation.

We present ab initio density functional theory (DFT) calculations on the effect of in-plane equi-biaxial strain on the structural and electronic properties of graphene-like GaN monolayer (ML-GaN). For compressive strain in excess of 7.2%, ML-GaN gets buckled; buckling parameter increases quadratically with compressive strain. The 2D bulk modulus of ML-GaN was found to be smaller than that of graphene and graphene-like ML-BN, which reflects weaker bond in ML-GaN. More importantly, the bandgap and effective masses of charge carriers in ML-GaN were found to be tunable by application of in-plane equi-biaxial strain. In particular, when compressive biaxial strain of about 3% was reached, a transition from indirect to direct bandgap-phase occurred with change in the value and nature of effective masses of charge carriers; buckling and tensile strain reduced the bandgap — the bandgap reduced to 50% of its unstrained value at 6.36% tensile strain and to 0 eV at an extrapolated tensile strain of 12.72%, which is well within its predicted ultimate tensile strain limit of 16%. These predictions of strain-engineered electronic properties of highly strain sensitive ML-GaN may be exploited in future for potential applications in strain sensors and other nanodevices such as the nano-electromechanical systems (NEMS).

In order to investigate the gas inertial effect on bearing capacity of acoustic levitation on condition of complex exciting shapes, a new kind of numerical model including inertial effect in cylindrical coordinates was proposed. The inertial terms in Navier–Stokes equations are packaged to derive modified Reynolds equations. The amplitudes of standing waves were tested by distance probe in experiment and film thickness equation were reconstructed by sum of the sinusoidal functions. The theoretical and experimental results implied that the inertial effect is strongly related to the exciting modal shapes. It is concluded that the proposal of modified Reynolds equation can provide more optimized numerical solutions to solve the problems about the deviation between theoretical and experimental data.

In this paper, we propose and apply a modified Rusanov scheme for numerical solution of the sediment transport model in one and two dimensions. This model consists of two parts, the first part is modeled by shallow water equations and the second part is described by the bed-load transport equation. The scheme consists of a predictor stage scheme including a local parameter of control. It is responsible for the numerical diffusion. To control this parameter, we use a strategy depending on limiter theory. In the corrector stage, we used special treatment of the bed to get a well-balanced discretization between the flux gradient and source term. Some numerical results are presented for the sediment transport equation in two forms called A-formulation and C-formulation. These results show that the finite volume scheme is accurate and robust for solving the sediment transport equation in one and two dimensions.

Quantum entanglement is studied in the neighborhood of a topological transition in some topological insulator models such as the two-dimensional Qi–Wu–Zhang model or Chern insulator. The system describes electrons hopping in two-dimensional chains. For the one-dimensional model case, there exist staggered hopping amplitudes. Our results show a strong effect of sudden variation of the topological charge Q in the neighborhood of phase transition on quantum entanglement for all the cases analyzed.

In a quantum measurement setting, it is known that environment-induced decoherence theory describes the emergence of effectively classical features of the quantum system–measuring apparatus composite system when the apparatus is allowed to interact with the environment. In [E. A. Galapon, Europhys. Lett. 113, 60007 (2016)], a measurement model is found to have the feature of inducing exact decoherence at a finite time via one internal degree of freedom of the apparatus provided that the apparatus is decomposed into a pointer and an inaccessible probe, with the pointer and the probe being in momentum-limited initial states. However, an issue can be raised against the model: while the factorization method of the time-evolution operator used there is formally correct, it is not completely rigorous due to some unstated conditions on the validity of the factorization in the Hilbert space of the model. Furthermore, no examples were presented there in implementing the measurement scheme in specific quantum systems. The goal of this paper is to re-examine the model and confirm its features independently by solving the von Neumann equation for the joint state of the composite system as a function of time. This approach reproduces the joint state obtained in the original work, leading to the same conditions for exact decoherence and orthogonal pointer states when the required initial conditions on the probe and pointer are imposed. We illustrate the exact decoherence process in the measurement of observables of a spin-1/2 particle and a quantum harmonic oscillator by using the model.