The European Physical Journal B最新文献

We present a model of speech perception which takes into account effects o correlations between sounds. Words in this model correspond to the attractors of a suitably chosen descent dynamics. The resulting lexicon is rich in short words, and much less so in longer ones, as befits a reasonable word length distribution. We separately examine the decryption of short and long words in the presence of mishearings. In the regime of short words, the algorithm either quickly retrieves a word, or proposes another valid word. In the regime of longer words, the behaviour is markedly different. While the successful decryption of words continues to be relatively fast, there is a finite probability of getting lost permanently, as the algorithm wanders round the landscape of suitable words without ever settling on one.

We present a Hamiltonian Monte Carlo study of doped perylene (textrm{C}_{20}textrm{H}_{12}) described with the Hubbard model. Doped perylene can be used for organic light-emitting diodes (OLEDs) or as acceptor material in organic solar cells. Therefore, central to this study is a scan over charge chemical potential. A variational basis of operators allows for the extraction of the single-particle spectrum through a mostly automatic fitting procedure. Finite chemical potential simulations suffer from a sign problem which we ameliorate through contour deformation. The on-site interaction is kept at (nicefrac {U}{kappa }=2). Discretization effects are handled through a continuum limit extrapolation. Our first-principles calculation shows significant deviation from non-interacting results especially at large chemical potentials.

We study high-order harmonic generation by optically driven one- and two-dimensional hydrogen-like atoms formed by Coulomb impurities in graphene. The time-dependent Dirac equations with Coulomb plus time-periodic monochromatic field potentials are solved for both cases. Such characteristics of the optical high harmonic generation, as average dipole moment and high harmonic generation spectra, are computed. A sketch for table-top experimental realization of the considered models is proposed.

This article aims to investigate the influence of vertical throughflow on the stability analysis of a biviscous Bingham fluid-saturated horizontal porous layer. Specifically, both linear and nonlinear stability thresholds are examined. The Darcy–Brinkman law is employed to formulate the momentum equation for the system. In this study, all three types of boundary conditions are considered: rigid-rigid, rigid-free, and free-free. The well-known energy method is applied to conduct the nonlinear stability analysis, while the linear stability analysis is carried out using the normal mode approach. The resultant eigenvalue problems are solved using the bvp4c-scheme in MATLAB 2022(a). The critical Rayleigh number and the corresponding wave numbers are obtained numerically by minimizing the neutral stability curves for both theories, and are calculated for the specified values of the flow-governing parameters, with the results presented graphically. It is observed that an increase in the Péclet number (vertical throughflow) delays the onset of convection, whereas an increase in the biviscous Bingham fluid parameter accelerates the onset of convection.

The optoelectronic and photocatalytic properties of rare-earth components (RE(=) Ce, La, and Sm) incorporated into the (hbox {SnS}_2) structure were investigated using first principles simulations. The TB-mBJ (Tran–Blaha modified Becke–Johnson) approach was used to explore several novel properties. The observed electronic band gap energy of pure (hbox {SnS}_2) is (E_g = 2.4) eV, which is in good agreement with the reported experimental value of (E_g = 2.44) eV. Results show that doping (hbox {SnS}_2) with RE elements at a concentration of 6.25% significantly reduces the electronic band gap compared to pristine (hbox {SnS}_2). This reduction can be attributed to the smaller ionic radii of (hbox {Ce}^{3+}), (hbox {La}^{3+}), and (hbox {Sm}^{3+}) ions, as well as the appearance of new states hybridized by RE-4f within the band gap, leading to a remarkable enhancement of the absorption spectra in the visible light range. Additionally, the calculated edge positions of the conduction band minimum (CBM) and the valence band maximum (VBM) relative to the normal hydrogen electrode (NHE) for both pristine and RE-doped (hbox {SnS}_2) are optimal for water splitting. Consequently, doping (hbox {SnS}_2) with rare-earth elements appears to be a promising strategy for enhancing its photocatalytic activity in the visible light spectrum.

This study introduces an innovative local statistical moment approach for estimating Kramers–Moyal coefficients, effectively bridging the gap between nonparametric and parametric methodologies. These coefficients play a crucial role in characterizing stochastic processes. Our proposed approach provides a versatile framework for localized coefficient estimation, combining the flexibility of nonparametric methods with the interpretability of global parametric approaches. We showcase the efficacy of our approach through use cases involving both stationary and non-stationary time series analysis. Additionally, we demonstrate its applicability to real-world complex systems, specifically in the energy conversion process analysis of a wind turbine.

The recent observation of magnetization plateaus in rare-earth metallic tetraborides has drawn considerable attention to this class of materials. In this work, we investigate the electronic structure of one such canonical system, (text {LuB}_{4}), using first-principles density functional theory together with Coulomb correlation and spin-orbit coupling (SOC). The electronic band structures show that (text {LuB}_{4}) is a non-magnetic correlated metal with a completely filled 4f shell. The projected density of states (DOS) shows a continuum at the Fermi level (FL), arising mainly from hybridized Lu d and B p orbitals, along with some discrete peaks well separated from the continuum. These peaks arise mainly due to core-level Lu s, p and 4f atomic orbitals. Upon inclusion of SOC, the discrete peak arising due to Lu p is split into two peaks with (j = 1/2), (j = 3/2) while the peak arising from Lu 4f orbitals splits into two peaks with (j = 5/2) and    (j = 7/2). These peaks will give rise to multiplet structure in core-level X-ray photo-emission spectroscopy and resonant inelastic X-ray scattering. Inclusion of correlation effects pushes the Lu 4f peak away from the FL, while the qualitative features remain intact. The present calculations will lead to an effective low-energy model for future investigation of transport and other properties.