物理最新文献

By combining first-principles computations with the semi-classical Boltzmann transport equations, a systematic investigation of the structural, electronic and thermoelectric properties of the MoSSe Janus monolayer is conducted under pressure. The monolayer semiconducting nature is indicated by the band gap value (E_g = 1.5 eV), which may be further tuned from 0.56 to 1.67 eV by applying pressure in the -3GPa to + 2GPa range. The figure of merit (ZT) for p (n)-type carriers at 300 K in the absence of pressure is computed to be 0.67 and 0.59. The power factor has enhanced from 16.59 (27.21) Wm⁻¹ K⁻² to 227.15 (159.50) Wm⁻¹ K⁻² for n (p)-type carriers by applying an external pressure of -1 GPa to the Janus monolayer. For n (p) -type doping at 300 K, the corresponding maximum value of ZT is 0.82 (0.78), which is 39% (14%) greater for n (p) type than for pure MoSSe Janus monolayer. When the pressure is increased to + 3 GPa, the value of ZT for n-type doping is further increased to 0.73, which is 24% higher than the value for pure monolayer. It is possible for a pure Janus monolayer to undergo n-type doping under pressure due to the shifting of the conduction band minima and valence band maxima. This study presents an attractive approach for manipulating the material thermoelectric properties through external pressure application.

In this paper we examine the thermal effects into the (e^{+}e^{-}rightarrow ell ^{+}ell ^{-}) scattering in a non-Hermitian extension of QED. We compute the thermal contributions to this scattering cross section within the Thermo Field Dynamics approach. In order to highlight the non-Hermitian effects we have considered some limits of interest: i) zero-temperature limit and high-energy limit and ii) high-temperature regime. Since this type of scattering possesses accurate experimental data for the cross section (for muon and tau at the final state) it can be used to set stringent bounds upon the non-Hermitian parameters.

Recent research on phosphorene synthesis, either single or multilayer, indicates that it has excellent potential for application in small structures. This study used sophisticated computations to examine the adhesion of CH₄, H₂S, and NH₃ molecules to a single layer of phosphorene. This study shows that phosphorene sensors are more effective at detecting certain chemicals than other comparable materials like graphene and MoS₂. After determining the optimal locations for these molecules to bind to phosphorene, discovered that the molecule-to-phosphorene charge transfer is essential for phosphorene's high adsorption capacity. Using a particular method, computed the relationship between the drain current and gate voltage for various gas concentrations on phosphorene. The transport properties show significant changes in the armchair direction of phosphorene, which aligns with its unique electronic structure, indicating major changes in current–voltage behavior when gas molecules are added. High sensitivity to gas adsorption of phosphorene of phosphorene, makes it an excellent gas sensor and shows its potential for use in electronic devices. The structural and electronic calculations in this study were performed using density functional theory with LDA and GGA approximations. The LDA approximation was used for structural optimization, while the GGA approximation was employed for a more accurate description of intermolecular and van der Waals interactions.

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In this paper, the variable-coefficient coherent coupled nonlinear Schrödinger system in weak birefringent fibers is investigated analytically. Lax pair and the N-fold potential transformation for the system are constructed. For the complex envelope of two interacting optical modes, exact vector one and two solitons and breathers are derived from the obtained potential transformation. Solitons and breathers with different dynamic properties are explored via adjusting the coefficient of the self-phase modulation and cross-phase modulation. Asymptotic analysis is used to discuss the interactions between two solitons. Two kinds of breathers with their existing conditions are analyzed.

During the era of NASA’s Apollo missions, Keith S. Runcorn proposed an explanation of discrepancy between the Moon’s negligible global magnetic field and magnetized samples of lunar regolith, based on identical vanishing of external magnetic field of a spherical shell, magnetized by an internal source which is no longer present. We revisit and generalize the Runcorn’s result, showing that it is a consequence of a (weighted) orthogonality of gradients of harmonic functions on a spherical shell in arbitrary number of dimensions. Furthermore, we explore bounds on external magnetic field in the case when the idealized spherical shell is replaced with a more realistic geometric shape and when the thermoremanent magnetization susceptibility deviates from the spherical symmetry. Finally, we analyse a model of thermoremanent magnetization acquired by crustal inward cooling of a spherical astrophysical body and put some general bounds on the associated magnetic field.

Based on the entropy of anti-de Sitter black hole, a new holographic dark energy model has been proposed. When the Hubble horizon and particle horizon are chosen as the IR cutoff, the late-time accelerated expansion of universe is realized. In this paper, we consider the Hubble horizon as the IR cutoff to investigate holographic inflation and slow-roll inflation in this model. We find that slow-roll inflation with the chaotic potential (V_{0}phi ^{n}) is favored by Planck results for some special cases, such as (n=1/3) and (n=1/2), while holographic inflation is not supported by Planck results. Then, we analyze the reheating temperature and the number of reheating e-folds in this model, and we find that the results favor the cases (n=1/3) and (n=1/2). Finally, we use the dynamical analysis method, statefinder diagnostic pairs, and the Hubble diagram to analyze this model. Our results indicate that when (b^{2}) takes a small value, this model cannot be distinguished from the standard (Lambda )CDM model and can serve as an alternative to it.

We review the works initiated and developed by L. P. Shilnikov on homoclinic chaos, highlighting his fundamental contributions to Poincaré homoclinics to periodic orbits and invariant tori. Additionally, we discuss his related findings in non-autonomous and infinite-dimensional systems. This survey continues our earlier review [1], where we examined Shilnikov’s groundbreaking results on bifurcations of homoclinic orbits — his extension of the classical work by A. A. Andronov and E. A. Leontovich from planar to multidimensional autonomous systems, as well as his pioneering discoveries on saddle-focus loops and spiral chaos.

In response to the urgent need for high-temperature-resistant, impact-resistant resin-based composites for the fan containment case of high thrust-to-weight ratio turbofan engines, numerical simulations were conducted for the oblique penetration of Ti- 6 Al- 4 V (TC4) flyers into CF/BMI laminates at different temperatures (200 °C and 300 °C) and variable yaw and pitch angles (0°, 10°, 20°, 30°, and 40°). A mesoscale model was established, considering the material laminate structure and surface weaving structure. The accuracy of the numerical simulation method was validated through experiments. The impact of different incident angles on the failure modes and energy absorption characteristics of the composite laminates at high temperatures were analyzed. The results indicate that, in terms of failure modes, under oblique penetration conditions, the failure modes of the laminate primarily include laminate cracking, shear plugging, fiber tensile fracture, and resin cracking. When the yaw angle is larger, local stresses cause cracking on the back of the target, mainly due to local shear plugging. When the pitch angle is larger, the laminate bending deformation is concentrated locally, and the overall deformation of the laminate is minimal. Shear and tensile failure occur between the fibers and resin matrix, causing the flyer to detach. The fibers on the upper side of the flyer experience deflection. As the temperature increases, the performance of the matrix is observed to decline, leading to thermal stress mismatch between the fibers and the matrix. Plastic deformation of the matrix occurs, resulting in a weakening of the interfacial bonding strength between the fibers and the matrix. Fiber bundles are found to fracture, and the phenomenon of interfacial debonding becomes more pronounced. In terms of energy absorption characteristics, as the yaw angle increases, the flyer is observed to consume more kinetic energy, and the strain energy and frictional dissipation energy of the laminate also increase. Under large-angle oblique penetration conditions, the laminate exhibits stronger impact resistance. As the pitch angle increases, the laminate kinetic energy absorption time is extended, frictional dissipation energy increases, the time for the flyer to penetrate the target is prolonged, and the remaining kinetic energy decreases. An increase in temperature leads to a reduction in the impact resistance of the laminate.

This study discusses an approach for estimation of the largest Lyapunov exponent for the mathematical model of the cardiovascular system. The accuracy was verified using the confidence intervals approach. The algorithm was used to investigate the effects of noises with different amplitudes and spectral compositions on the dynamics of the model. Three sets of parameters are considered, corresponding to different states of the human cardiovascular system model. It is shown that, in each case, the model exhibited chaotic dynamics. The model gave different responses to the changes in the characteristics of the noise, when using different sets of parameters. The noise had both constructive and destructive effects, depending on the parameters of the model and the noise, by, respectively, amplifying or inhibiting the chaotic dynamics of the model.