Catálogo de publicaciones - revistas

<jats:p>A phase-field-based lattice Boltzmann model is proposed for the interface capturing of multi-phase flows based on the conservative Allen–Cahn equation (ACE). By adopting the improved form of a relaxation matrix and an equilibrium distribution function, the time derivative <jats:italic>∂<jats:sub>t</jats:sub> </jats:italic>(<jats:italic>ϕ <jats:bold>u</jats:bold> </jats:italic>) induced by recovering the diffusion term in ACE is eliminated. The conducted Chapman–Enskog analysis demonstrates that the correct conservative ACE is recovered. Four benchmark cases including Zalesak’s disk rotation, vortex droplet, droplet impact on thin film, and Rayleigh–Taylor instability are investigated to validate the proposed model. The numerical results indicate that the proposed model can accurately describe the complex interface deformation.</jats:p>

<jats:p>In fast <jats:italic>Z</jats:italic>-pinches, rise time of drive current plays an important role in development of magneto-Rayleigh-Taylor(MRT) instabilities. It is essential for applications of <jats:italic>Z</jats:italic>-pinch dynamic hohlraum (ZPDH), which could be used for drivinginertial confinement fusion (ICF), to understand the scaling of rise time on MRTs. Therefore, a theoretical model for nonlinear development of MRTs is developed according to the numerical analysis. It is found from the model that the implosion distance <jats:italic>L</jats:italic> = <jats:italic>r</jats:italic> <jats:sub>0</jats:sub> – <jats:italic>r</jats:italic> <jats:sub>mc</jats:sub> determines the development of MRTs, where <jats:italic>r</jats:italic> <jats:sub>0</jats:sub> is the initial radius and <jats:italic>r</jats:italic> <jats:sub>mc</jats:sub> is the position of the accelerating shell. The current rise time <jats:italic>τ</jats:italic> would affect the MRT development because of its strong coupling with the <jats:italic>r</jats:italic> <jats:sub>0</jats:sub>. The amplitude of MRTs would increase with the rise time linearly if an implosion velocity is specified. The effects of the rise time on MRT, in addition, are studied by numerical simulation. The results are consistent with those of the theoretical model very well. Finally, the scaling of the rise time on amplitude of MRTs is obtained for a specified implosion velocity by the theoretical model and numerical simulations.</jats:p>

<jats:p>Atmospheric pressure micro-discharges in helium gas with a mixture of 0.5% water vapor between two pin electrodes are generated with nanosecond overvoltage pulses. The temporal and spatial characteristics of the discharges are investigated by means of time-resolved imaging and optical emission spectroscopy with respect to the discharge morphology, gas temperature, electron density, and excited species. The evolution of micro-discharges is captured by intensified CCD camera and electrical properties. The gas temperature is diagnosed by a two-temperature fit to the ro-vibrational OH(A<jats:sup>2</jats:sup>Σ<jats:sup>+</jats:sup>–X<jats:sup>2</jats:sup>Π, 0–0) emission band and is found to remain low at 425 K during the discharge pulses. The profile of electron density performed by the Stark broadening of H<jats:sub> <jats:italic>α</jats:italic> </jats:sub> 656.1-nm and He I 667.8-nm lines is uniform across the discharge gap at the initial of discharge and reaches as high as 10<jats:sup>23</jats:sup> m<jats:sup>−3</jats:sup>. The excited species of He, OH, and H show different spatio-temporal behaviors from each other by the measurement of their emission intensities, which are discussed qualitatively in regard of their plasma kinetics.</jats:p>

<jats:p>In recent years, transition metal silicides have become the potential high temperature materials. The ternary silicide has attracted the attention of scientists and researchers. But their inherent brittle behaviors hinder their wide applications. In this work, we use the first-principles method to design four vacancy defects and discuss the effects of vacancy defects on the structural stability, mechanical properties, electronic and thermodynamic properties of hexagonal Cr<jats:sub>5</jats:sub>BSi<jats:sub>3</jats:sub> silicide. The data of lattice vibration and thermodynamic parameters indicate that the Cr<jats:sub>5</jats:sub>BSi<jats:sub>3</jats:sub> with different atomic vacancies can possess the structural stabilities. The different atomic vacancies change the mechanical properties and induce the Cr<jats:sub>5</jats:sub>BSi<jats:sub>3</jats:sub> to implement the brittle-to-ductile transition. The shear deformation resistance and volume deformation resistance of Cr<jats:sub>5</jats:sub>BSi<jats:sub>3</jats:sub> are weakened by different vacancy defects. But the brittleness behavior is remarkably improved. The structural stability and brittle-to-ductile transition of Cr<jats:sub>5</jats:sub>BSi<jats:sub>3</jats:sub> with different vacancies are explored by the electronic structures. Moreover, the thermal parameters indicate that the Cr<jats:sub>5</jats:sub>BSi<jats:sub>3</jats:sub> with vacancies exhibit different thermodynamic properties with temperature rising.</jats:p>

<jats:p>In the ring-shaped Su–Schrieffer–Heeger (SSH) double-chain, the quantum interference between the two different electron tunneling paths of the upper and lower chains has an important influence on the electron transport properties of non-trivial topological edge states. Here, we have studied the electron transport signatures of non-trivial topological edge states in a ring-shaped SSH double-chain system based on the wave-guide theory and transfer-matrix method. In the ring-shaped SSH double-chain with the upper chain being different from the lower one, it is demonstrated that the electron transmission probability displays the four and two resonance peaks associated with the non-trivial topological edge states in the weak and strong coupling regimes, respectively. Whereas in the case of the upper chain being the same as the lower one, the two transmission resonance peaks associated with the non-trivial topological edge states in the weak coupling regime are only found, and that in the strong coupling regime disappear that originated from the destructive interference between the two different electron tunneling paths of the upper and lower chains. Consequently, the variation of the number of transmission resonance peaks associated with the non-trivial topological edge states in the weak and strong coupling regimes suggests that an alternative scheme for detecting non-trivial topological edge states in the ring-shaped SSH double-chain system.</jats:p>

<jats:p>We investigate the impact of Ni insertion on the structural, optical, and magnetic properties of Ba<jats:sub>0.8</jats:sub>La<jats:sub>0.2</jats:sub>Fe<jats:sub>12–<jats:italic>x</jats:italic> </jats:sub>Ni<jats:italic> <jats:sub>x</jats:sub> </jats:italic>O19 hexaferrites (Ni substituted La-BaM hexaferrites). Samples were prepared using the conventional co-precipitation method and sintered at 1000 °C for 4 hours to assist the crystallization process. An analysis of the structure of the samples was carried out using an x-ray diffraction (XRD) spectrometer. The M-type hexagonal structure of all the samples was confirmed using XRD spectra. The lattice parameters <jats:italic>a</jats:italic> and <jats:italic>c</jats:italic> were found to be in the ranges of 5.8925±0.001 nm–5.8952±0.001 nm and 23.2123±0.001 nm–23.2219±0.001 nm, respectively. The M-type hexagonal nature of the prepared samples was also indicated by the presence of corresponding FT-IR bands and Raman modes in the FT-IR and Raman spectra, respectively. EDX results confirmed the successful synthesis of the samples according to the required stoichiometric ratio. A UV-vis spectrometer was used to record the absorption spectra of the prepared samples in the wavelength range of 200 nm–1100 nm. The optical energy bandgap of the samples was found to be in the range of 1.21 eV–3.39 eV. The <jats:italic>M–H</jats:italic> loops of the samples were measured at room temperature at an applied magnetic field range of 0 kOe–60 kOe. A high saturation magnetization of 99.92 emu/g was recorded in the sample with <jats:italic>x</jats:italic> = 0 at a microwave operating frequency of 22.2 GHz. This high value of saturation magnetization is due to the substitution of La<jats:sup>3+</jats:sup> ions at the spin-up (12<jats:italic>k</jats:italic>, 2<jats:italic>a</jats:italic>, and 2<jats:italic>b</jats:italic>) sites. The Ni substitution is proven to be a potential candidate for the tuning of the optical and magnetic parameters of M-type hexaferrites. Therefore, we suggest that the prepared samples are suitable for use in magneto-optic applications.</jats:p>

<jats:p>The excited-state intramolecular proton transfer of 2-(2′-hydroxyphenyl)benzoxazole dye in different solvents is investigated using ultrafast femtosecond transient absorption spectroscopy combined with quantum chemical calculations. Conformational conversion from the syn-enol configuration to the keto configuration is proposed as the mechanism of excited-state intramolecular proton transfer. The duration of excited-state intramolecular proton transfer is measured to range from 50 fs to 200 fs in different solvents. This time is strongly dependent on the calculated energy gap between the N-S<jats:sub>0</jats:sub> and T-S<jats:sub>1</jats:sub> structures in the S<jats:sub>1</jats:sub> state. Along the proton transfer reaction coordinate, the vibrational relaxation process on the S<jats:sub>1</jats:sub> state potential surface is observed. The duration of the vibrational relaxation process is determined to be from 8.7 ps to 35 ps dependent on the excess vibrational energy.</jats:p>

<jats:p>With the aid of the Painlevé analysis, we obtain residual symmetries for a new (3+1)-dimensional generalized Kadomtsev–Petviashvili (gKP) equation. The residual symmetry is localized and the finite transformation is proposed by introducing suitable auxiliary variables. In addition, the interaction solutions of the (3+1)-dimensional gKP equation are constructed via the consistent Riccati expansion method. Particularly, some analytical soliton-cnoidal interaction solutions are discussed in graphical way.</jats:p>

<jats:p>The appearance of rumors intensifies people’s panic and affects social stability. How to control the spread of rumors has become an important issue which is worth studying. In order to more accurately reflect the actual situation in the real world, a stochastic model incorporating media coverage and Lévy noise is proposed to describe the dynamic process of rumor propagation. By introducing two control strategies of popular science education and media coverage in an emergency event, an near-optimal control problem that minimizes the influence and control cost of rumor propagation is proposed. Sufficient conditions for near-optimal control of the model are established by using a Hamiltonian function. Then the necessary conditions for near-optimal control are obtained by using the Pontryagin maximum principle. Finally, the effect of popular science education, media coverage and Lévy noise on rumor propagation process control is verified by numerical simulation.</jats:p>

<jats:p>Expectation values of single electron and interelectronic geometric quantities such as 〈<jats:italic>r</jats:italic>〉, 〈<jats:italic>r</jats:italic> <jats:sub>12</jats:sub>〉, 〈<jats:italic>r</jats:italic> <jats:sub>&lt;</jats:sub>〉, 〈<jats:italic>r</jats:italic> <jats:sub>&gt;</jats:sub>〉, 〈cos<jats:italic>θ</jats:italic> <jats:sub>12</jats:sub>〉 and 〈<jats:italic>θ</jats:italic> <jats:sub>12</jats:sub>〉 are calculated for doubly excited 2p<jats:italic>n</jats:italic> p<jats:sup>1</jats:sup> <jats:italic>P</jats:italic> <jats:sup>e</jats:sup> (3 ≤ <jats:italic>n</jats:italic> ≤ 5), 2p<jats:italic>n</jats:italic> p<jats:sup>3</jats:sup> <jats:italic>P</jats:italic> <jats:sup>e</jats:sup> (2 ≤ <jats:italic>n</jats:italic> ≤ 5) and 2p<jats:italic>n</jats:italic>d<jats:sup>1,3</jats:sup> <jats:italic>D</jats:italic>° (3 ≤ <jats:italic>n</jats:italic> ≤ 5) states of helium using Hylleraas-<jats:italic>B</jats:italic>-spline basis set. The energy levels converge to at least 10 significant digits in our calculations. The extrapolated values of geometric quantities except for 〈<jats:italic>θ</jats:italic> <jats:sub>12</jats:sub>〉 reach 10 significant digits as well; 〈<jats:italic>θ</jats:italic> <jats:sub>12</jats:sub>〉 reaches at least 7 significant digits using a multipole expansion approach. Our results provide a precise reference for future research.</jats:p>