Modern Physics Letters B

Aiming at the problem of low quality of coherent demodulation transmission signal of digital signal in the background of Levy noise, this paper proposes a new method of 4FSK signal reception based on adaptive tristable stochastic resonance (SR) system. The bit error rate (BER) of output signals of adaptive tristable SR system model and the traditional modulation model are compared by simulation. The numerical simulation results show that compared with the traditional model, the output BER of the 4FSK signal after demodulation of the adaptive tristable SR system model is reduced by 4% compared with the traditional model. The time domain image of 4FSK signal is clearer, the burrs are significantly reduced and the spectral amplitude of 4FSK signal is greatly improved. The success of this experiment suggests a strong promise of SR systems for digital signal detection in impact noise.

We present structural, electronic, magnetic, elastic and transport properties of tetragonal Mn₂PtSn (MPS) bulk material in stannite (ST) phase, we will use a FP-LAPW method based on DFT under GGA, TB-mBJ and GGA+U as implemented in the WIEN2k code. From the ferromagnetic state, band structure (spin-down/spin-up channel) calculations reveal an indirect bandgap/zero-bandgap. Mn₂PtSn shows inverse tetragonal crystal structures with ferromagnetic spin order at zero temperature. The elastic stability criterion shows that the MPS crystal satisfies the mechanical stability under applied at 0GPa. The related mechanical properties such as bulk modulus (B), shear modulus (G), Young’s modulus (E), and Poisson’s ratio ($\nu$) are also studied for polycrystalline of MPS; the calculated B/G value (B/$G=2.96$) shows that MPS behaves in a ductile manner. Hence, this study of transport properties suggests their potential thermoelectric applications at high temperatures. To our knowledge, the results obtained show that this ternary alloy is advantageous for materials employed in spintronic devices.

In this paper, we will investigate the structural, electronic, mechanical, magnetic and optical properties of Heusler Mn₂NiAl (MNA) compound using the Perdew–Burke–Ernzerhof generalized gradient approximation (PBE-GGA) of the full potential linearized augmented plane-wave method for exchange and use correlations, modified Becke–Johnson and GGA+U Hubbard parameter. The calculated band structure (BS) and density of states (DOS) of MNA showed a metallic (GGA), nearly half-metallic (mBJ) and half metallic (GGA+U) behavior. Moreover, the magnetic computed magnetic moments by GGA+U are higher compared to GGA and mBJ results. Bulk modulus, shear modulus, Voigt and Reuss polycrystalline elastic modulus, Debye temperature, sound velocities, the melting temperatures, $B/G$ ratio, Young’s modulus and Poisson’s ratio were obtained. The elastic anisotropy of MNA alloy was analyzed using 2D and 3D figures of directional dependence of Poisson’s ratio, shear modulus, linear compressibility and Young’s modulus. Studies have shown that the Heusler material MNA has magnetic and anisotropic properties and is mechanically stable.

The flow structures of jet impingement dominate heat and mass transfer process, even the whole thermal performance. In this study, we have inspected the flow structures and mechanism of nanofluid jet impingement onto a dimpled target surface with different design parameters. Investigations are performed for the relative depth of dimple ($\delta /D$), the jet-to-plate spacing ($H/d$), nanoparticle volume concentration ($\varphi$), and Reynolds number (Re) ranging to explore the mechanism of flow structure variations. Results indicate that these parameters have a significant effect on the flow structure of nanofluid jet impingement near the dimpled target surface. The flow begins to separate after passing the edge of the dimple along with the curvature of a dimple. $\delta /D$ will affect the form and location of flow separation and reattachment, and $\varphi$ will affect the intensity of separation flow. The length of the flow separation bubble varies in different $H/d$ cases. When $H/d$ increases, the impinging energy and the velocity near the dimple edge decreases. The different Re has little effect on the length of the flow separation bubble and the tendency of the pressure coefficient (Cp). These results can provide further mechanism inspiration for the design of the flow structure of nanofluid jet impingement.

It is found that without any additional assumptions, Nernst’s equation can be re-deduced from the experimental data obtained from the thermodynamic systems at ultra-low temperatures, which is different from the derivation processes in textbooks and literature, and consequently, the physical content included by Nernst’s equation should not be referred to as Nernst’s postulate or Nernst’s theorem. It should be renamed as the Nernst statement. This discovery will play an important role in improving the theoretical framework of thermodynamics. It can effectively prevent some artificial assumptions into the third law of thermodynamics, making it a true reflection of the objective world. It solves the awkward problem caused by using a thermodynamic theorem as the core contents of a thermodynamic law for over one hundred years.

The motivation of this paper is to explore an oscillatory flow of a magnetohydrodynamics (MHD) couple stress fluid with heat and mass transfer analyses through a porous medium. The modified Darcy–Brinkman couple stress fluid model is employed. There could be many potential applications of this study, such as thermal system, solidification of liquid crystals, cooling of metallic plates in a bath, exotic lubricants and colloidal solutions. In the wake of these potential applications, the study of MHD couple stress fluid flow with additional diffusing components has been found to be innovative and very interesting in the analysis of the influence of combined magnetic effects, couple stress fluid and two solutes. A governing coupled nonlinear partial differential equation with boundary constraints represents the modeled flow problem. In addition, these equations are converted into nondimensional form by employing the suitable nondimensionalizing quantities. It is possible to attain analytic solutions to the dimensionless equations that control the liquid flow, and the consequences of the flow’s confines on velocity, temperature, concentration and skin friction profile are examined and also the results are discussed through graphs. It is noteworthy that when the injection level on the heated plate is increased, the skin friction on each channel plate also increases.

In this study, a terahertz dual-band–high-gain, multi-input–multi-output (MIMO) antenna with two and four input ports was realized, with gain values of up to 7.16dBi and 6.44dBi, respectively. This represents an increase in gain of 102.4% and 81.8%, respectively, compared to single-input port antennas. By calculating and analyzing the voltage standing wave ratio (VSWR), gain, envelope correlation coefficient (ECC), and diversity gain, the two MIMO antennas achieved perfect impedance matching at their resonance points. Moreover, the interference between the elements of the MIMO antenna was small, and an isolation effect between the units was realized. These MIMO antennas can achieve multiple input signals to regulate the antenna radiation performance and improve signal strength and quality. In addition, they possess good development prospects for achieving high-speed data transmission in the terahertz band and in mobile communication.

In this paper, the motion of inertial particles in three-dimensional (3D) unsteady cylindrical wake flow is investigated by a two-way coupled Eulerian–Lagrangian approach. At different flow Reynolds numbers (Re), the corresponding striking dynamic property and dispersion mechanism of four particle classes have been studied, with inertia parameterized by means of Stokes number (Sk). It is found that inertial particles with lower Stokes number are expelled from vortex cores, and coherent voids encompass the local Kármán vortex cells. As Stokes number increases, a low velocity particle channel could be formed, which almost coincides with the results in the literature. Moreover, with the increase of Reynolds number, numerous irregular coherent voids are observed in the cylinder wake, and the high-speed particles follow the fluid flow closely when they are contained in the vortices. Although the centrifugal force of Kármán vortex cells significantly affects the dynamics of inertial particles, the fluid flow modulation is believed to be responsible for the distinctive particle dispersion patterns in the vortex streets. For particles with medium inertia, the two-way coupled modulation weakens the centrifugal effect of vortex structures on the particles. This trend declines with the increase of Reynolds number, and vanishes with light particles, while both two-way coupled modulation and the centrifugal effect of vortex structures are almost equally effective with heavy particles. The investigations contribute to a better understanding of the particle-laden flows in practical applications, which will benefit the optimized design of certain machinery and equipment for the industry.

With the rapid development of electronics, the application and research of two-dimensional materials have been at the forefront of the world’s scientific research. Black phosphorus (BP) has the advantages of large specific surface area, anisotropy, band tunability, high electrical conductivity and high theoretical specific capacity, which make it very promising for research in the fields of medicine, aerospace and electrochemistry. This paper calculates the electronic structure and adsorption properties of BP in water for different heavy metal ions of Pb${}^{2+}$, Hg${}^{2+}$ and Cd${}^{2+}$, including adsorption energy, bandgap, electron density and Mulliken population analysis, based on the first-principles approach of density generalized theory. First principles are quantum mechanical calculations based on density functional theory (DFT), which is a dominant well-developed method in the field of materials simulations, with low errors and high efficiency, especially in systems containing metallic particles. The results showed that the Pb${}^{2+}$ adsorption system in water was more stable than the Hg${}^{2+}$ adsorption system and the Cd${}^{2+}$ adsorption system. The bandgap values of 0.617, 0.785 and 0.715eV of BP after adsorption of Pb${}^{2+}$, Hg${}^{2+}$ and Cd${}^{2+}$ in water are smaller compared to 0.891eV of intrinsic BP, and its properties change from direct bandgap semiconductor to indirect bandgap semiconductor. The higher the stability of a system for the adsorption of different heavy metal ions by BP, the higher the internal electron activity of the adsorption system and the amount of electron transfer. Meanwhile, it is concluded that the electrons mainly transfer from P to heavy metal ions in all the adsorption systems.

The electron transfer of the BP-Pb${}^{2+}$, Hg${}^{2+}$, and Cd${}^{2+}$ adsorption system occurs mainly in the p, s, and s/p orbitals, respectively. The above content investigated the electronic structure changes and internal electron transfer of heavy metal ions adsorbed by black phosphorus in water, expecting to provide a new reference basis for the detection of heavy metal ions in industrial wastewater using black phosphorus.

This study deals with the Lonngren wave equation, which is used to model the transmission of electrical signals in a type of semiconductor material called a tunnel diode. The aim of this study is to produce dark soliton, singular soliton, trigonometric, complex rational solutions to the Lonngren wave equation by using the sub-equation method. Graphs representing the Lonngren wave are drawn by giving different values to the variables in the solutions obtained. Graphs are presented using a special package program. In the light of the data obtained as a result of the study, it is thought that this new method used in the research of the solution of the Lonngren wave equation will contribute to the literature.

Quantum orthogonal arrays are combinatorial designs with a remarkable class of genuinely multipartite highly entangled states. In this paper, we propose the method for constructing maximally multi-qubit entangled state through phase parameters of orthogonal arrays. Using this method, we not only determine that maximally n-qubit entangled state, but also find the $n-1$ orthogonal array that gives maximally $n-1$ entangled states. Such states play an important role in quantum theory with a high degree of multipartite entanglement.

Noise pollution is growing nowadays and there is always a conflict between ventilation and noise insulation. The advances in acoustic metamaterials provide an effective solution for this conflict. In this paper, we propose a metastructure with protruded necks based on Helmholtz resonance. Sound transmission loss (STL) of 13 dB at low-frequency of 488Hz is obtained in experiment with the ventilation of 20%, which is in good agreement with the simulation. It is revealed that introduction of protruded neck can reduce the resonant frequency. Sound absorption is the main mechanism for noise insulation at low frequency. Next, the effects of geometric parameters on sound insulation are discussed. A reduction in cross-sectional area of neck, an increase in neck length, and an increase in ventilation all lead to a decrease in both resonant frequencies and STL amplitudes. Finally, a two-layer structure is constructed by the proposed metastructure with different neck length in each unit. Both the amplitude and frequency range of STL are enlarged. These results exhibit a practical application for ventilated metastructure in sound insulation at low frequency.