Modern Physics Letters B

We show a possible relationship between the deformation factor $\tau$ and the inverse of the de Gennes parameter $\gamma$ in the Ginzburg–Landau model for a superconducting meso-film and meso-disk in the presence of an external magnetic field in the Meissner state. It is shown that there is a lineal relationship between $\tau$ and $\gamma$ when a forced model is considered. This being the case, the curves for the magnetization M (H) and the magnetic susceptibility ${\chi }_m(H)$ are presented for several values of $\tau$ and $\gamma$, showing an acceptable qualitative fit between these curves.

The $sinh$-Gordon model is an important model in special nonlinear partial differential equations (PDEs) which is arising in solid-state physics, mathematical physics, fluid dynamics, fluid flow, differential geometry, quantum theory, etc. The exact solutions in the type of solitary wave and elliptic functions solutions are created of $sinh$-Gordon model by employing modified direct algebraic scheme. Moments of a few solutions are also depicted graphically. These solutions helps the physicians and mathematicians to understand the physical phenomena of this model. This technique can be utilized on other models to launch further exclusively novel solutions for other categories of nonlinear PDEs occurring in mathematical Physics.

Rational solutions of nonlinear evolution (NLE) equations have been the subject of numerous research papers. In this paper, a new generalized Kadomtsev–Petviashvili (KP) equation with diverse applications is investigated analytically. Multiple solitons, breather and rogue waves, and complexitons as special cases of rational solutions to the new generalized KP equation are formally extracted with the help of symbolic computations. Some two- and three-dimensional figures are considered to show the dynamics of rational solutions in the new generalized KP equation.

Speech is a convenient medium for communication among human beings. Speaker recognition is a process of automatically recognizing the speaker by processing the information included in the speech signal. In this paper, a new approach is proposed for speaker recognition through speech signal. Here, a two-level approach is proposed. In the first-level, the gender of the speaker is recognized, and in the second-level speaker is recognized based on recognized gender at first-level. After recognizing the gender of the speaker, search space is reduced to half for the second-level as speaker recognition system searches only in a set of speech signals belonging to identified gender. To identify gender, gender-specific features: Mel Frequency Cepstral Coefficients (MFCC) and pitch are used. Speaker is recognized by using speaker specific features: MFCC, Pitch and RASTA-PLP. Support Vector Machine (SVM) and Gaussian Mixture Model (GMM) classifiers are used for identifying the gender and recognizing the speaker, respectively. Experiments are performed on speech signals of two databases: “IIT-Madras speech synthesis and recognition” (containing speech samples spoken by eight male and eight female speakers of eight different regions in English language) and “ELSDSR” (containing speech samples spoken by five male and five female in English language). Experimentally, it is observed that by using two-level approach, time taken for speaker recognition is reduced by 30–32% as compared to the approach when speaker is recognized without identifying the gender (single-level approach). The accuracy of speaker recognition in this proposed approach is also improved from 99.7% to 99.9% as compared to single-level approach. It is concluded through the experiments that speech signal of a minimum 1.12 duration (after neglecting silence parts) is sufficient for recognizing the speaker.

In this paper, the effects of heat transfer and Hall current on the sinusoidal motion of solid particles through a planar channel has been discussed. The walls of the channel are considered as compliant under the effects of magnetohydrodynamics. The mathematical formulation has been performed using energy equation, momentum equation, and Ohm’s law. The modeled equations are further modified by taking the assumption of a zero Reynolds number and long wavelength. Numerical shooting technique has been employed to solve the nonlinear differential equations. The impact of all the emerging parameters such as wall rigidity, wall tension, mass characterization, Hall parameter, Hartmann number, Weissenberg number, particle volume fraction, Prandtl number, and Eckert number, respectively. Particularly, we discussed their effects on velocity and temperature profile.

This paper focuses on the efficiency improvement of a centrifugal fan used in a vacuum cleaner. In order to check the performance of the centrifugal fan system, computational fluid dynamics (CFD) analysis is used. The numerical simulation with CFD tool is carried out with RNG $k-𝜀$ two-equation turbulence model based on Reynolds-averaged Navier–Stokes equations. To perform the coupling between rotating impeller and stationary area, the multiple reference frame (MRF) model is used. The numerical results of the fan are validated against with experimental results and are found to be highly reliable. The design and optimization of diffuser and impeller of a centrifugal fan are realized by using numerical investigations. For reducing the kinetic energy loss inside the fan, a guide baffle is added to optimize diffuser. The optimization results show that overall efficiency of the fan is improved by 5.27% and considering the lower efficiency of impeller caused by blockage at the blade inlet, etc., the design of impeller with long-short blades is proposed. Several cases of affecting factors under different operating conditions are simulated. Relative length (denoted as $\sigma$) and circumferential position of short blades are chosen as design variables. It is found that the efficiency of a fan with a relative length of 0.7 can be increased by 9.34%, and the best circumferential position of short blades is between two adjacent long blades.

A modified diffusion-limited aggregation (DLA) model for two-dimensional (2D), three-dimensional (3D) fractal growth and 3D island growth was established based on the DLA model in this paper. The number of particles $N$ and the size of the box size $V$ (related to side length $L$), which are related to film thickness, are considered in the study. The simulation results are a good reflection of the actual experimental results. The results show that the particle number and simulation box size can affect the fractal morphology and fractal dimension of the film, and also the 2D to 3D transformation. In addition, the critical particle number $N_{\mathrm{\text{critical}}}$ and the critical box size $V_{\mathrm{\text{critical}}}$ during the transformation process are also given.

The structural, electronic, mechanical and thermodynamic properties for ${\mathrm{\text{Al}}}_{23}{\mathrm{\text{REMg}}}_{34}$ and ${\mathrm{\text{Al}}}_{24}{\mathrm{\text{Mg}}}_{33}\mathrm{\text{RE}}$ (RE = Sc, Y, La, Sm and Gd) compounds have been calculated by first-principles theory. The obtained structural parameters and elastic constants of two kinds of doped ${\mathrm{\text{Al}}}_{12}{\mathrm{\text{Mg}}}_{17}$ are compared with some theoretical and experimental data. The electronic structure analysis, such as density of states, explains the bonding character of Al–Mg–RE. All the doped ${\mathrm{\text{Al}}}_{12}{\mathrm{\text{Mg}}}_{17}$ are influenced by the high-energy electrons directly. Furthermore, the basic mechanical properties which are derived from the elastic constants and the thermal stability of doped ${\mathrm{\text{Al}}}_{12}{\mathrm{\text{Mg}}}_{17}$ are discussed. The predicted brittleness of ${\mathrm{\text{Al}}}_{23}{\mathrm{\text{REMg}}}_{34}$ and ${\mathrm{\text{Al}}}_{24}{\mathrm{\text{Mg}}}_{33}\mathrm{\text{RE}}$ is consistent with the available experiments.

In this research work, we investigated the higher-order nonlinear Schrödinger equation (NLSE) with fourth-order dispersion, self-steepening, nonlinearity, nonlinear dispersive terms and cubic-quintic terms which is described as the propagation of ultra-short pulses in fiber optics. We apply the modification form of extended auxiliary equation mapping method to find the new exact and solitary wave solutions of higher-order NLSE. As a result, new solutions are obtained in the form of solitons, kink–anti-kink type solitons, bright–dark solitons, traveling wave, trigonometric functions, elliptic functions and periodic solitary wave solutions. These new different types of solutions show the power and fruitfulness of this new method and also show two- and three-dimensional graphically with the help of computer software Mathematica. These new solutions have many applications in the field of physics and other branches of physical sciences. We can also solve other higher-order nonlinear partial differential equations (NPDEs) involved in mathematical physics and other various branches of physical sciences with this new technique.

Generally, due to the interference of different harmonic emission peaks (HEPs), the intensity of high-order harmonic spectrum cannot keep enhancing as the pulse intensity increases. Thus, in this paper, a potential method to obtain an intense spectral continuum and isolated attosecond pulse (IAP) by selecting single HEP has been theoretically investigated. First, we choose the harmonic cutoff and the harmonic intensity from the optimal single-color laser intensity as the referenced values. Next, by properly choosing a lower-intensity negative chirped pulse, we see that the harmonic cutoff from this field is similar as that from the referenced field. Moreover, the spectral continuum is contributed by single HEP. However, the intensity of the spectral continuum from the negative chirped pulse is lower than that from the referenced field. As the pulse duration of the chirped pulse increases, the similar harmonic cutoff can also be found by using a much lower-intensity negative chirped pulse. However, the intensity of the spectral continuum is decreased compared with that from the shorter chirped pulse duration. Further, with the introduction of an IR or UV controlling pulse, the intensity of the spectral continuum can be enhanced up to the referenced value. Moreover, the longer the pulse duration of the controlling pulse is used, the lower the controlling pulse intensity is needed. Also, due to the UV resonance ionization, much lower UV intensity is needed to enhance the harmonic yield compared with that for adding IR controlling pulse case. All in all, the total laser intensity of the combined field (the fundamental pulse + the controlling pulse) is lower than that of the referenced field. Most importantly, the signal of the spectral continuum is only coming from single HEP, which can support the generations of intense IAPs with the durations of 30 as.

The model of optical propagation in nonlocal parabolic law medium is described by nonlinear Schrödinger equation with high-order nonlinear terms. Exact optical propagation patterns are constructed by proposing a general complex trial equation method. These results show rich optical propagation patterns of the model.

Searching two-dimensional (2D) magnetic materials with high spin polarization is important for the development and application of next-generation spintronic devices. Here, based on spin-polarized density functional theory calculations, the stability, electronic structure and magnetic properties of Mn-doped and Mn–NM (NM = B, C, N and S) co-doped monolayer WSe₂ are investigated in detail. The results indicate that the Mn–S co-doped MoSe₂ configuration has the lowest formation energy in the whole chemical potential range and easily spontaneously forms under thermodynamic equilibrium conditions. Obviously, the Mn-doped WSe₂ configuration exhibits magnetic half-metallicity characters with a completely spin polarization at the Femi level $(E_F)$, which can be attributed to that the electrons partially occupy the bonding states consisting of Mn $a_1$ states at the $E_F$. For the Mn–C and Mn–S co-doped configurations, the Mn $d_{xy}$ and $d_z^2$ orbitals strongly hybridize with the C or S spin-up $p_z$ orbital at the $E_F$, which induces strong spin exchange splitting and eventually gives rise to the magnetic semiconductor character. However, the Mn–B and Mn–N co-doped configurations exhibit completely symmetrical spin-up and spin-down channel of $a_1$, $a_2$, $a_3$ and $a_4$ states due to the effective charge compensation between Mn and B or N atoms. These studies provide a new class of 2D magnetic materials for future spintronics devices.

The noise and linearity performance of a MEMS accelerometer is a critical issue for land seismic acquisition applications. Incorporating closed-loop force feedback is an effective way to enhance those performances. However, additional electrode to exert the electrostatic force is typically not available and residue displacement of proof mass would introduce significant nonlinearity to the closed-loop transfer function, impairing the efficiency of the method. This paper proposes a switched-capacitor closed-loop readout interface for MEMS accelerometer which greatly alleviates those problem. First, the proposed system incorporates a time-multiplexing technique, thus the sensing and force feedback can be realized using the same electrode and get separated in time sequence. Furthermore, the cross-coupling of high-voltage feedback signal and weak sensing signal can be minimized. Second, a correlated double sampling (CDS) technique and a PID control mechanism is introduced in the loop. Thus, the two sources of residue displacement: interface mismatch and insufficient loop gain can be well-suppressed. The test results show that the proposed closed-loop MEMS accelerometer can achieve an SNR better than 120 dB, with an in-band noise spectral density lower than 500 ng/Hz${}^{1/2}$.

This work focused on slip flow over a non-Newtonian nanofluid fluid flow past a stretching sheet with particles–liquid suspension. The convective boundary condition is taken into account. Similarity transformations are utilized to reduce the nonlinear partial differential equations into a set of nonlinear ordinary differential equations. Runge–Kutta–Fehlberg scheme is used to get the numerical solution. Important parameters are analyzed through graphs and skin friction coefficient. Nusselt numbers are presented in tables. Investigation reveals that slip parameter decreases the velocity field and Biot number increases the temperature field.