Modern Physics Letters B

When acoustic wave is normally reflected from wave thinner medium of semi-infinite, the acoustic pressure phase of reflection wave changes $\pi$, or half-wave loss, when acoustic wave is reflected from wave denser medium of semi-infinite, the acoustic pressure phase of the reflection wave is invariant, or no wave loss, when acoustic wave is reflected from wave thinner (or denser) medium of finite thickness, the phase of the reflection wave changes. According to the acoustic wave theory, we derived the acoustic wave reflection coefficient and the phase shift, and designed various kinds of phase shifters. The simulation results show that acoustic phase shifters can cloak acoustic wave.

In order to reveal the impact of preceding vehicle’s velocity on traffic flow, an extended car-following model considering preceding vehicle’s velocity feedback control is proposed in this paper. The linear stability criterion of the new model is derived through control theory method and it shows that the feedback control signal impacts the stability of traffic flow. Numerical simulation results is in good agreement with the theoretical analysis, which prove that a smaller negative feedback control of the preceding vehicle’s velocity can enhance the stability of traffic flow, while a smaller positive feedback control of the preceding vehicle’s velocity can exacerbate traffic congestion. Moreover, the reaction coefficients of straight and curved road conditions also play an important role in the stability of traffic flow.

Effect of ultrasonic impact treatment (UIT) on microstructure and fatigue properties of the aluminum alloy 6082 was studied at room temperature. The change of microstructure on the surface and the grain size after impact treatment was observed by metallographic microscope and transmission electron microscopy, respectively. The residual stress was measured by residual stress tester. The experimental results show that the UIT can lead to obvious plastic deformation layer in the treated surface, and nanocrystals were formed. Compressive residual stress of 50.4 MPa was maximum at the surface after the UIT. With an impact current of 1.0 A and impact time of 2 min, compared with untreated specimens, the fatigue strength of the 6082 aluminum alloy joint increases by about 11.18%. The fracture position for the treated specimen has been changed, the crack initiation is seen in the weld toe surface for the as-welded joint, and the crack initiation in the sub-surface for the treated specimen is comparable to the as-welded joint fatigue.

The lattice parameters, structural stability, mechanical properties, hardness and electronic structure of WCoB with Cr alloying were investigated by using first-principles calculations. The Cr atom was selected to replace 0, 1, 2, 3, 4 Co atoms in WCoB crystal and 0, 1, 2 Co atoms in W₂CoB₂ crystal. The calculated cohesive energy and formation enthalpy showed that all structures can retain good structural stability with different Cr doping content. The calculated mechanical properties showed Cr doping will decrease the shear modulus, Young’s modulus, bulk modulus and hardness, but increase the ductility. The larger number of valence electrons of Cr led to the increasing of bond covalence and population. According to the electronic structures analysis, the nonmetal–metal hybridization and metal–metal interactions contributed to relatively high toughness.

In traffic systems, cooperative driving has attracted the researchers’ attention. A lot of works attempt to understand the effects of cooperative driving behavior and/or time delays on traffic flow dynamics for specific traffic flow models. This paper is a new attempt to investigate analyses of linear stability and weak nonlinearity for the general car-following model with consideration of cooperation and time delays. We derive linear stability condition and study how the combinations of cooperation and time delays affect the stability of traffic flow. Burgers’ equation and Korteweg de Vries’ (KdV) equation for car-following model considering cooperation and time delays are derived. Their solitary wave solutions and constraint conditions are concluded. We investigate the property of cooperative optimal velocity (OV) model which estimates the combinations of cooperation and time delays about the evolution of traffic waves using both analytic and numerical methods. The results indicate that delays and cooperation are model-dependent, and cooperative behavior could inhibit the stabilization of traffic flow. Moreover, delays of sensing relative motion are easy to trigger the traffic waves; delays of sensing host vehicle are beneficial to relieve the instability effect to a certain extent.

To research the effects of properties of silt particles on cavitating flow, silt-laden cavitation flow in one 3D nozzle is simulated. Silt mean diameters are 0.005 mm, 0.007 mm, 0.009 mm, 0.010 mm, 0.012 mm, 0.013 mm, 0.015 mm, 0.020 mm, 0.026 mm, 0.030 mm, 0.035 mm, 0.040 mm, 0.046 mm, 0.050 mm and 0.056 mm. Silt concentrations vary from 1.0% to 10%. To measure the effects of silt particles, vapor contents under pure water cavitation flow and silt-laden cavitation flow conditions are calculated and compared. Results show that silt particles first promote the development of cavitation then inhibit the evolution of cavitation with the increase of silt concentration. Silt particles promotion scope decreases gradually and inhibition span increases constantly with the increase of silt mean diameter. Cavitation nuclei, vortices, slip velocity, virtual mass force and Saffman lift force have a closed relation with the promotion of silt particles. Vortices, viscosity and silt abrasion deeply influence the inhibition of cavitation.

In this paper, we consider the perturbed nonlinear Schrödinger equation with a bounded potential, which is an important model in fiber communication. By considering the ansatz method, we obtain the bright and dark soliton solutions of the equation. By employing the sub-equation method, we also construct its complexitons solutions. Finally, the explicit power series solution is also derived with its convergence analysis. It is hoped that our results can help enrich the nonlinear dynamical behaviors of the perturbed nonlinear Schrödinger equation.

In this paper, the (3+1)-dimensional Boussinesq equation which can describe the propagation of gravity waves on the surface of water is investigated. Using the Bell polynomials, the bilinear form of the (3+1)-dimensional Boussinesq equation is obtained and the lump soliton solutions for the equation are derived by means of the quadratic function method. As an important integrable property, the Bäcklund transformation for the (3+1)-dimensional Boussinesq equation is constructed by the Bell polynomials considering the constraints on the derivatives with respect to spatial and temporal variables. Through the relationship between the Bell polynomials and the Hirota bilinear operators, the bilinear Bäcklund transformation for the (3+1)-dimensional Boussinesq equation is given.

The morphological stability of lamellar eutectic growth with the anisotropic effect of surface tension is studied by means of the interfacial wave (IFW) theory developed by Xu in the 1990s. We solve the related linear eigenvalue problem for the case that the Peclet number is small and the segregation coefficient parameter is close to the unit. The stability criterion of lamellar eutectic growth with the anisotropic surface tension is obtained. The linear stability analysis reveals that the stability of lamellar eutectic growth depends on a stability critical number ${𝜀}_{\ast }$. Similar to the case of isotropic surface tension, the system involves two types of global instability mechanisms: the “exchange of stability” invoked by the non-oscillatory, unstable modes and the “global wave instabilities” invoked by four types of oscillatory unstable modes, namely antisymmetric–antisymmetric (AA-), symmetric–symmetric (SS-), antisymmetric–symmetric (AS-) and symmetric–antisymmetric (SA-) modes. The anisotropic surface tension, by decreasing the corresponding stability critical number ${𝜀}_{\ast }$, stabilizes the “exchange of stability” mechanism and “global wave instability” mechanism invoked by AA-, SA- and SS-modes. However, by increasing the corresponding stability critical number ${𝜀}_{\ast }$, the anisotropic surface tension destabilizes the “global wave instability” mechanism invoked by AS-mode.

This paper recommends a method to reduce harmonic distortion of MEMS accelerometer. The fifth-order MEMS accelerometer interface circuit designed in this work used the Cascade-of-Integrators, Feedforward modulation structure. This paper analyzes and calculates the main sources of HD, the unstable problem brought by the vacuum encapsulation sensitive structure. The use of front-phase compensation and the increase in loop forward gain helps ensure the system’s stability as well as reduce the system harmonic distortion. Simulink is used to get the simulation results. After harmonic optimization, the third harmonic reached −141.83 dB, the Signal-to-Noise-and-Distortion-Ratio rose to 118.1 dB, the noise density is under 200 ng/Hz${}^{1/2}$, the effective number of bits rose up to 19.33 bits.

We solve exactly the master equation of the degenerate and nondegenerate parametric oscillator in the presence of a squeezed reservoir. We show that the formal solutions of both systems can be obtained in terms of the density operator by applying squeeze transformations and using the superoperators formalism.

This paper describes the mechanical and thermophysical properties of actinide monocarbides AnCs (An=Np and Cm) as a function of temperature and crystallographic direction. The temperature-dependent second- and third-order elastic constant (SOECs and TOECs) have been computed first using Coulomb and Born–Mayer potential up to second nearest neighbor. SOECs have been applied to find out mechanical constant such as bulk modulus, shear modulus, tetragonal modulus, Poisson’s ratio and Zener anisotropy for the prediction of futuristic performance of the NpC and CmC. We also found the value of G/B $>$ 0.59 for the chosen materials, which indicates that NpC and CmC have brittle nature. The computed elastic constants are further applied directly to indirectly find out the ultrasonic velocity, Grüneisen parameters, pressure derivative, Debye temperature, micro-hardness, Breazeale’s nonlinearity parameter, thermal relaxation time and thermal conductivity. These evaluated parameters were finally used to compute ultrasonic attenuation of the NpC and CmC along $〈100〉$, $〈110〉$ and $〈111〉$ directions at room temperature. The behavior of the obtained results of this investigation has been compared with similar type of materials.

We compute the momentum distribution of a homogeneous Fermi gas at unitarity in the normal phase within the framework of the non-self-consistent T-matrix approximation with particle-hole fluctuation. From the large-momentum behavior of momentum distribution, we obtain the contact for the unitary Fermi gas. We also compare our results with experimental data and other theoretical predictions.

Using a microscopic model, taking into account the spin–phonon interactions and the Green’s function technique, we have studied the phonon properties of pure and ion-doped SnO₂ nanoparticles (NPs). The phonon energy of SnO₂ NPs decreases whereas the damping increases with decreasing particle size. Near the Curie temperature in the NPs, there appears an anomaly in the phonon energy $\omega (T)$ and damping $\gamma (T)$. The phonon properties are very sensitive to the anharmonic spin–phonon interaction R. They can increase or decrease for $R>0$ or $R<0$ with increasing of temperature, respectively. In dependence of the radius of the doping ions, the phonon energies $\omega$ could be reduced (Co, Fe, Sm, Nd) or enhanced (Cu). The phonon damping is always enhanced in the doped NPs. In summary, due to the size and temperature effects, we obtain changes in the phonon energy and damping in pure SnO₂ NPs, whereas in ion-doped ones, the doping effects strengthen these properties.