Catálogo de publicaciones - revistas

<jats:title>Abstract</jats:title> <jats:p>The synthesis of multi-color laser pulses has been developed as a promising way to improve the low conversion efficiency of high-order harmonic generation (HHG). Here we systematically study the effect of laser focus in the two-color waveform on the generation of macroscopic HHG in the soft X-rays. We find that the dependence of HHG yields on laser focus at low or high gas pressure is sensitive to the characteristics of single-atom harmonic response, in which “short”- or “long”-trajectory emissions can be selectively controlled by changing the waveform of two-color synthesized laser pulse. We uncover the phase-matching mechanism of HHG in the gas medium by examining the propagation of two-color waveform and the evolution of time-frequency emissions of high-harmonic field. We further reveal that the nonlinear effects, such as geometric phase, atomic dispersion, and plasma defocusing, are responsible for the modification of two-color waveform upon propagation. This work can be used to find a better macroscopic conditions for generating soft X-ray HHG by employing the two-color optimized waveform.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Grand canonical Monte Carlo simulation(GCMCs) is utilized for studying hydrogen storage gravimetric density by the pha-graphene at different metal densities, temperatures, and pressures. It is demonstrated that the optimum adsorbent location of the Li atom is the center of the seven-membered ring of pha-graphene. The binding energy of Li-decorated pha-graphene is larger than the cohesive energy of Li atoms, implying that Li can be distributed on the surface of pha-graphene without forming metal clusters. We fitted the force field parameters of Li and C atoms at different positions and performed GCMCs to study the absorption capacity of H<jats:sub>2</jats:sub>. The capacity of hydrogen storage was studied by the different density Li decoration. The maximum hydrogen storage capacity of 4Li-decorated pha-graphene was 15.88 wt% at 77 K and 100 bar. The enthalpy values of adsorption at the three densities are in the ideal range of 15 kJ/mol-25 kJ/mol. The GCMC results at different pressures and temperatures show that with the increase of Li decorative density, the hydrogen storage gravimetric ratio of pha-graphene decreases but can reach the standard of 2025 DOE (5.5 wt%). Therefore, pha-graphene is considered as a potential hydrogen storage material.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Experiments and simulation studies on 283-MeV I ion induced single event effects of SiC MOSFETs were carried out. When the cumulative irradiation fluence of SiC MOSFET reaches 5×10<jats:sup>6</jats:sup> ion·cm<jats:sup>-2</jats:sup>, the drain-gate channel current increases under 200 V drain voltage, the drain-gate channel current and the drain-source channel current increased under 350 V drain voltage. The device occurred single event burnout under 800 V drain voltage, resulting in a complete loss of breakdown voltage. Combined with emission microscope, scanning electron microscope and focused ion beam analysis, the device with increased drain-gate channel current and drain-source channel current was found to have drain-gate channel current leakage point and local source metal melt, the device with single event burnout was found to have local melting of its gate, source, epitaxial layer and substrate. Combining Monte Carlo simulation and TCAD electrothermal simulation, it is found that the initial area of single event burnout may occur at the source-gate corner or the substrate-epitaxial interface, electric field and current density both affect the lattice temperature peak. The excessive lattice temperature during the irradiation process appeared at the local source contact, which led to the drain-source channel damage. And the excessive electric field appeared in the gate oxide layer, resulting in drain-gate channel damage.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>In addition to non-radiative guided modes, two-dimensional photonic-crystal slabs support guided resonant ones which can radiate into free space. From the polarization states of these guided resonances, a polarization field on a photonic band can be constructed in momentum space. Momentum-space polarization fields display complicated configurations and patterns with different types of polarization singularities inside, shedding new light on the manipulations of light flows. In this review, we summarize the recent research progress on momentum-space polarization fields and singularities in two-dimensional photonic-crystal slabs, focusing on their unique optical properties and potential applications as well.</jats:p>

<jats:p>Proton transfer (PT) is a process of fundamental importance in hydrogen (H)-bonded systems. At cryogenic or moderate temperatures, pronounced quantum tunneling may happen due to the light mass of H. Single PT processes have been extensively studied. However, for PT involving multiple protons, our understanding remains in its infancy stage due to the complicated interplay between the high-dimensional nature of the process and the quantum nature of tunneling. Cyclic H-bonded systems are typical examples of this, where PT can happen separately via a “stepwise” mechanism or collectively via a “concerted” mechanism. In the first scenario, some protons hop first, typically resulting in metastable intermediate states (ISs) and the reaction pathway passes through multiple transition states. Whilst in the concerted mechanism, all protons move simultaneously, resulting in only one barrier along the path. Here, we review previous experimental and theoretical studies probing quantum tunneling in several representative systems for cyclic PT, with more focus on recent theoretical findings with path-integral based methods. For gas-phase porphyrin and porphycene, as well as porphycene on a metal surface, theoretical predictions are consistent with experimental observations, and enhance our understanding of the processes. Yet, discrepancies in the PT kinetic isotope effects between experiment and theory appear in two systems, most noticeably in water tetramer adsorbed on NaCl (001) surface, and also hinted in porphycene adsorbed on Ag (110) surface. In ice <jats:italic>I</jats:italic> <jats:sub>h</jats:sub>, controversy surrounding concerted PT remains even between experiments. Despite of the recent progress in both theoretical methods and experimental techniques, multiple PT processes in cyclic H-bonded systems remain to be mysterious.</jats:p>