Catálogo de publicaciones - revistas

<jats:title>Abstract</jats:title> <jats:p>Based on the phase-change material Ge<jats:sub>2</jats:sub>Sb<jats:sub>2</jats:sub>Te<jats:sub>5</jats:sub> (GST), achromatic metasurface optical device in the longer-infrared wavelength is designed. With the combination of the linear phase gradient GST nanopillar and the adjustment of the crystalline fraction <jats:italic>m</jats:italic> value of GST, the polarization insensitive achromic metalenses and beam deflector metasurface within the longer-infrared wavelength 9.5μm to 13μm are realized. The design results show that the achromatic metalenses can be focused on the same focal plane within the working waveband. The simulation calculation results show that the full-width at half-maximum (FWHM) of the focusing spot reaches the diffraction limit at each wavelength. In addition, the same method is also used to design a broadband achromatic beam deflector metasurface with the same deflection angle of 19°. The method proposed in this article not only provides new ideas for the design of achromatic metasurfaces, but also provides new possibilities for the integration of optical imaging, optical coding and other related optical systems.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>MoS<jats:sub>2</jats:sub>, a transition metal dichalcogenide (TMDC), has attracted a significant amount of attention due to its direct bandgap, tunability and optical properties. Recently, a novel structure consisting of MoS<jats:sub>2</jats:sub> and noble metal nanoclusters has been reported. Inspired by this, first-principles calculations were implemented to predict the structures of M<jats:sub>6</jats:sub>X<jats:sub>2</jats:sub> and M<jats:sub>6</jats:sub>XX' (M = Au, Ag; X, X' = S, Se). The calculated bandgap, band edge position, and optical absorption of these structures prove that the silver compounds (Ag<jats:sub>6</jats:sub>X<jats:sub>2</jats:sub> and Ag<jats:sub>6</jats:sub>XX') have great potential for catalytic water splitting. In addition, biaxial strain (tensile strain and compressive strain) was applied to adjust the properties of these materials. The bandgap presents a quasi-linear trend with increasing applied strain intensity. Moreover, the transition between the direct and indirect bandgap was found. The outstanding electronic and optical properties of these materials provide strong evidence for the application in microelectronic devices, photoelectric devices, and photocatalytic materials.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We study the cross-stitch flatband lattice subject to the quasiperiodic complex potential exp(<jats:italic>ix</jats:italic>). We first identify the exact expression of quadratic mobility edges through analytical calculation, then verify theoretical predictions by numerically calculating the inverse participation ratio. Further more, we study the relationship between the real-complex spectrum transition and the localization-delocalization transition, and demonstrate that mobility edges in this non-Hermitian model not only separate localized from extended states but also indicate the coexistence of complex and real spectrum.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>In this paper, four intelligent optimization algorithms are compared by searching for control pulses to achieve the preparation of target quantum states for closed and open quantum systems, which include differential evolution (DE), particle swarm optimization (PSO), quantum-behaved particle swarm optimization (QPSO), and quantum evolutionary algorithm (QEA). We compare their control performance and point out their differences. By sampling and learning for uncertain quantum systems, the robustness of control pulses found by these four algorithms is also demonstrated and compared. The resulting research shows that the QPSO nearly outperforms the other three algorithms for all the performance criteria considered. This conclusion provides an important reference for solving complex quantum control problems by optimization algorithms and makes the QPSO be a powerful optimization tool.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Pedestrian movement simulation models are used for various purposes, such as building evacuation, transportation engineering, safety management of large events. It also provides effective means to uncover underlying mechanisms of collective behaviors. This paper presents a modified heuristics-based model in which potential collisions are explicitly considered during the moving process. Meanwhile, a series of simulations were conducted in two typical scenarios to demonstrate the influence of critical parameters on model performance. We found that when facing a wide obstacle in a corridor, the larger the visual radius, the earlier the pedestrian starts to make a detour. In addition, when a pedestrian observes a large crowd walking towards him, he chooses to make a detour and move in the flow in a uniform direction. Furthermore, the model can reproduce lane formation pedestrian flow phenomena in relatively high-density situations. With the increase of pedestrian visual radius and the weight of potential collision resistance, more stable pedestrian lanes and less moving-through-the-counterflow pedestrians can be observed. In terms of model validation, the density-speed relationship of simulation results agrees well with that of the published empirical data. Our results demonstrate that the modified heuristics-based model has overcome the deficiency of the original model, which is capable of reproducing more realistic pedestrian movement behavior.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Considering the fact that memristors have the characteristics similar to biological synapses, a fractional-order multistable memristor is proposed in this paper. It is verified that the fractional-order memristor has multiple local active regions and multiple stable hysteresis loops, and the influence of fractional-order on its nonvolatility is also revealed. Then by considering the fractional-order memristor as an autapse of HR neuron model, a fractional-order memristive neuron model is developed. The effects of the initial value, external excitation current, coupling strength and fractional-order on the firing behavior are discussed by time series, phase diagram, Lyapunov exponent and inter spike interval (ISI) bifurcation diagram. Three coexisting firing patterns, including irregular A-periodic bursting, A-periodic bursting and chaotic bursting, dependent on the memristor initial values, are observed. It is also revealed that the fractional-order can not only induce the transition of firing patterns, but also change the firing frequency of the neuron. Finally, a neuron circuit with variable fractional-order is designed to verify the numerical simulations.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Antiferromagnetic LiErF<jats:sub>4</jats:sub> has attracted extensive attention due to its dipolar interaction domination and quantum fluctuations action. In present work, the crystal structure, cryogenic magnetic properties, and magnetocaloric effect (MCE) of polycrystalline LiErF<jats:sub>4</jats:sub> compound were investigated. Crystallographic study shows that the compound crystallizes in the tetragonal scheelite structure with <jats:italic>I4</jats:italic> <jats:sub> <jats:italic>1</jats:italic> </jats:sub>/<jats:italic>a</jats:italic> space group. It exhibits an antiferromagnetic (AFM) phase transition around 0.4 K, accompanied by a giant cryogenic MCE. At 1.3 K, the maximum values of magnetic entropy change are 24.3 J/kg K, 33.1 J/kg K, and 49.0 J/kg K under the low magnetic field change of 0-0.6 T, 0-1 T, and 0-2 T, respectively. The giant MCE observed above <jats:italic>T</jats:italic> <jats:sub>N</jats:sub> is probably due to the strong quantum fluctuations, which cause a large ratio of the unreleased magnetic entropy existing above the phase transition temperature. The outstanding low-field MCE below 2 K makes the LiErF<jats:sub>4</jats:sub> compound an attractive candidate for the magnetic refrigeration at ultra-low temperature.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Excited-state intramolecular proton transfer (ESIPT) molecules are broadly application to UV absorbers, fluorescence sensing, and lighting materials. In previous work, the fluorescence colors of Oxazoline-substituted hydroxyfluorenes and Hydroxylated benzoxazole were diversified by adding the π-conjugation. There is intriguing that the mechanism of diversified fluorescence colors induced by ESIPT. Here, the density functional theory (DFT) and time-dependent DFT (TDDFT) are advised to identify the effects of π-conjugation on ESIPT and photophysical properties. The stabilized geometrical configurations, frontier molecular orbitals (FMOs) isosurfaces, and O−H stretching vibration frequencies analyses demonstrate that PT processes are more active in S<jats:sub>1</jats:sub> state. Through constructing the minimum energy pathways of ESIPT processes, we find that the calculated peak of enol and keto fluorescence of NO-OH is distinctly bathochromic-shift relative to the Oxa-OH configuration when adding π-conjugation-substitution, it means that π-conjugation-substitution can diversify the fluorescence color. We hope our studies can establish new channels to devise the ESIPT-based molecules</jats:p>

<jats:title>Abstract</jats:title> <jats:p>A novel lattice hydrodynamic model is raised by integrating the cooperative deviation of density and optimal flux under V2X environment. According to theoretical analysis, the stability conditions and the mKdV equations affected by the cooperative deviation of traffic information are explored. And the density wave, hysteresis loop and energy consumption of traffic flow have been investigated via numerical simulation. The results indicate that the cooperative deviation of density and optimal flux can effectively alleviate traffic congestion. More importantly, our new consideration can reduce fuel consumption and exhaust emissions under V2X environment.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Based on the self-terminating thermal oxidation assisted wet etching technique, two kinds of enhancement mode Al<jats:sub>2</jats:sub>O<jats:sub>3</jats:sub>/GaN MOSFETs with sapphire substrate and Si substrate are manufactured. The study found that the performance of sapphire substrate device is better than that of silicon substrate, Comparing with these two devices, the maximum drain current of sapphire substrate device(401 mA/mm) is 1.76 times that of silicon substrate device(228 mA/mm), and the field‐effect mobility (<jats:italic>μ</jats:italic> <jats:sub> <jats:italic>FEmax</jats:italic> </jats:sub>) of sapphire substrate device(176 cm<jats:sup>2</jats:sup>/Vs) is 1.83 times that of silicon substrate device(96 cm<jats:sup>2</jats:sup>/Vs). The conductive resistance of silicon substrate device is 21.2Ω·mm, while that of sapphire substrate device is only 15.2Ω·mm, which is 61% that of silicon substrate device. The significant performance differences between sapphire substrate and Si substrate were related to the differences in interface and border traps near Al<jats:sub>2</jats:sub>O<jats:sub>3</jats:sub>/GaN interface. Experimental studies shown that: (1) interface/border trap density in the sapphire substrate device is one order of magnitude lower than Si substrate device. (2) Both the border traps in Al<jats:sub>2</jats:sub>O<jats:sub>3</jats:sub> dielectric near Al<jats:sub>2</jats:sub>O<jats:sub>3</jats:sub>/GaN and the interface traps in Al<jats:sub>2</jats:sub>O<jats:sub>3</jats:sub>/GaN interface has a significantly effect on device channel mobility. (3) The properties of gallium nitride materials on different substrates are different due to wet etching. The paper research results are use for reference to the further optimizing the performance of silicon substrate devices.</jats:p>