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Interfacial coupling effects in g-C3N4/SrTiO3 nanocomposites with enhanced H2 evolution under visible light irradiation
摘要： The g-C3N4/SrTiO3 nanocomposite is an important material in photocatalysis, but little attention has been paid to their interfacial interaction in photocatalytic reaction. Herein, we prepare the g-C3N4/SrTiO3 nanocomposites via a two-step mechanically milling and calcination process. The composite exhibited the highest H2 evolution activity superior to that of the pure g-C3N4 and SrTiO3 in the visible light. The results of UV-vis DRS, PL and photoelectrochemical measurements demonstrated that g-C3N4/SrTiO3 exhibited more visible light adsorption and faster photo-generated charge transfer. Furthermore, with the help of a strong built-in electric field presenting in the g-C3N4/SrTiO3 interface, the photo-generated electrons flow to the SrTiO3 from g-C3N4, leading to the highly-efficient electron separation and more H2O molecules photo-reduction to H2. This work explicates the significant role of built-in electric field in H2 evolution on g-C3N4/SrTiO3 photocatalyst.
关键词： built-in electric field,g-C3N4,visible light,H2 evolution,SrTiO3
更新于2025-09-19 17:15:36
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Enhanced photocatalytic hydrogen evolution of?CdWO4 through polar organic molecule modification
摘要： In this work, a polar molecule 4-mercaptobenzoic acid (4-MBA) is anchored on the surface of CdWO4 by forming CdeS and WeS bond. Photocatalytic hydrogen evolution is significantly enhanced (about 3.41 times) after the modification. The reason is due to the modification of 4-MBA, which results in a polar surface and built-in electric field. The polar surface is confirmed by the steady state and time-resolved PL spectra, Voc and SHG results.
关键词： CdWO4,Photocatalytic hydrogen evolution,4-mercaptobenzoic acid,Surface modification,Built-in electric field
更新于2025-09-19 17:15:36
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Internal electromagnetic waves, energy trapping, and energy release in simple time-domain simulations of single particle scattering.
摘要： During the decay phase of the interaction of a femto-second Gaussian pulse with a single spherical particle, the presence of quasi-periodic short oscillatory bursts of electromagnetic energy at points in the near field outside the particle have been observed in three-dimensional simulations. Analogous behavior can be very easy produced and understood in simple one-dimensional scattering calculations. In two dimensions the situation immediately becomes more complicated and interesting. Here we discuss results from two-dimensional pseudo-spectral time-domain simulations of scattering from circular, elliptical, and hexagonal particles with the real index of refraction m=1.3. Our focus is on how energy initially trapped within a particle after interaction with an incident Gaussian pulse is released over time, and we show two kinds of events that can result in 'bursts' of energy release from the particles: (i) the coalescence of counter-propagating wave-packet-like electromagnetic field structures that have maximum amplitude near the surface of the particle, and (ii) encounters of individual packets with surface regions of high curvature. The coalescence events in the circular case show the dynamical origin of a two-dimensional form of 'photonic nanojet.' The two-dimensional simulations make clear the reason for quasi-periodic intermittent bursts at fixed near-field points outside the particle. Examination of field evolution shows that distinct near-surface internal field maxima, ostensibly the 'source' of the emission bursts, are in fact inter-connected by caustic-like internal field structures that extend throughout the particle and have complex time evolution. The revealed intricacy of these connections suggests that understanding the origins of pulsed emissions in three dimensions, even for simple particle geometries, may be quite challenging.
关键词： caustic evolution,photonic nanojet,single particle scattering,femtosecond Gaussian pulses,internal electromagnetic waves
更新于2025-09-19 17:15:36
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One Pot Assembly of Vertical Embedded MoS2/Graphene Hetero-structure and Its High Performance for Hydrogen Evolution Reaction
摘要： Two-dimensional molybdenum disulfide has great potential to replace rare precious metals for hydrogen evolution reaction. Herein, we report a one pot assembly strategy for in-situ growing vertical embedded MoS2 nanocrystals on graphene surface. The resultant sandwiched architecture could not only expose more active sites within MoS2 edge, but also reduce stacking tendency of the layer-structured graphene support, leading to a significant improvement in HER performance. The materials showed an over-potential of 142 mV at 10 mA·cm?2 and a Tafel slope of 68 mV·dec?1, which are among the best results ever obtained by the similar materials. Moreover, this method is facile, environmental friendly and suitable for mess production, making it attractive for practical applications.
关键词： Graphene,Hydrogen evolution reaction,MoS2,Electrocatalysis,Sandwiched structure
更新于2025-09-19 17:15:36
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Synthesis and Characterization of a Rare Transition-Metal Oxothiostannate and Investigation of Its Photocatalytic Properties
摘要： The new transition-metal oxothiostannate [Ni(cyclen)(H2O)2]4[Sn10S20O4]·～13H2O (1) was prepared under hydrothermal conditions using Na4SnS4·14H2O as the precursor in the presence of [Ni(cyclen)(H2O)2](ClO4)2·H2O. Compound 1 comprises the [Sn10S20O4]8? anion constructed by the T3-type supertetrahedron [Sn10S20] and the [Sn10O4] anti-T2 cluster. Channels host the H2O molecules, and the sample can be reversibly dehydrated and rehydrated without significantly affecting the crystallinity of the material. 119Sn NMR spectroscopy of an aqueous solution of Na4SnS4·14H2O evidences that between 25 and 120 °C only [SnS4]4? and [Sn2S6]4? anions are present. In further experiments, hints were found that the formation of the tin oxosulfide ions depends on the Ni2+-centered complexes. Compound 1 exhibits promising photocatalytic properties for the visible-light-driven hydrogen evolution reaction, with 18.7 mmol·g?1 H2 being evolved after 3 h.
关键词： photocatalytic hydrogen evolution,oxothiostannate,NMR spectroscopy,hydrothermal synthesis,transition-metal complex
更新于2025-09-19 17:15:36
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[IEEE 2019 Compound Semiconductor Week (CSW) - Nara, Japan (2019.5.19-2019.5.23)] 2019 Compound Semiconductor Week (CSW) - Buried-ridge-waveguide Type GaInAsP/InP Membrane Distributed-Reflector Lasers for Reduction of Differential Resistance
摘要： Utilizing cumulative correlation information already existing in an evolutionary process, this paper proposes a predictive approach to the reproduction mechanism of new individuals for differential evolution (DE) algorithms. DE uses a distributed model (DM) to generate new individuals, which is relatively explorative, whilst evolution strategy (ES) uses a centralized model (CM) to generate offspring, which through adaptation retains a convergence momentum. This paper adopts a key feature in the CM of a covariance matrix adaptation ES, the cumulatively learned evolution path (EP), to formulate a new evolutionary algorithm (EA) framework, termed DEEP, standing for DE with an EP. Without mechanistically combining two CM and DM based algorithms together, the DEEP framework offers advantages of both a DM and a CM and hence substantially enhances performance. Under this architecture, a self-adaptation mechanism can be built inherently in a DEEP algorithm, easing the task of predetermining algorithm control parameters. Two DEEP variants are developed and illustrated in the paper. Experiments on the CEC’13 test suites and two practical problems demonstrate that the DEEP algorithms offer promising results, compared with the original DEs and other relevant state-of-the-art EAs.
关键词： evolutionary computation,differential evolution (DE),evolution path (EP),Cumulative learning
更新于2025-09-19 17:13:59
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Surface morphology evolution with laser surface re-melting in selective laser melting
摘要： Laser surface re-melting (LSR) is a promising method for improving the surface quality of parts fabricated via selective laser melting (SLM). In this research, LSR under different linear energy densities (LEDs) was conducted numerically and experimentally. Additionally, double LSR using an LED of 225 J/m was conducted, and the surface morphology, melt pool flow behavior, melt pool size, and thermal behavior was investigated. The results show that for LSR with a low LED, the maximum flow velocity and maximum temperature was rather low, such that the surface was not reconfigured sufficiently. Furthermore, the surface between adjacent scan paths may not be entirely re-melted with a low LED, because the melt pool width was insufficient. However, when the LED was high, the maximum temperature gradient was rather large, giving rise to cracks. For double LSR with a moderate LED, the surface morphology was quite smooth and did not contain obvious defects. The results indicate that LSR is a feasible method for improving the surface quality, and repeated LSR with a moderate LED and small hatch space is recommended in SLM.
关键词： Selective laser melting,Laser surface re-melting,Melt pool flow,Surface morphology evolution
更新于2025-09-19 17:13:59
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Wideband Hybrid Envelope Tracking Modulator With Hysteretic-Controlled Three-Level Switching Converter and Slew-Rate Enhanced Linear Amplifier
摘要： A wideband hybrid Envelope tracking (ET) modulator utilizing a hysteretic-controlled three-level switching converter (3L-SWC) and a slew-rate enhanced linear ampli?er (LA) are presented. In addition to smaller ripple and lower losses of 3L-SWCs, employing the proposed hysteresis control results in a higher speed loop and wider bandwidth converter, enabling over 80 MHz of switching frequency. A concurrent sensor circuit monitors and regulates the ?ying capacitor voltage VCF and eliminates the conventionally required calibration loop to control it. The hysteretic-controlled 3L-SWC provides a high percentage of power ampli?er (PA) supply load current with lower ripple, reducing the LA high-frequency current and ripple cancellation current, improving the overall system ef?ciency. A slew-rate enhancement (SRE) circuit is employed in the LA, resulting in slew rate of over 307 V/μs and bandwidth of over 275 MHz for the LA. The SRE circuit provides a parallel auxiliary current path directly to the gate of the class-AB output stage transistors, speeding-up the charging or discharging of output without modifying the operating point of the remaining LA, while maintaining the quiescent current of the class-AB stage. The supply modulator is fabricated in a 65-nm CMOS process. The measurement results show the tracking of long-term evolution (LTE)-40-MHz envelope with 93% peak ef?ciency at 1-W output power, while the SRE is disabled. Enabling the SRE, it can track LTE-80-MHz envelope with peak ef?ciency of 91%.
关键词： long-term evolution (LTE),LTE-advanced,hysteresis control,Envelope tracking (ET),supply modulator,power ampli?er (PA),three-level switching converter (3L-SWC),slew-rate enhancement (SRE),hybrid
更新于2025-09-19 17:13:59
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Comparative study on parameter extraction of photovoltaic models via differential evolution
摘要： Parameter extraction of photovoltaic (PV) models, which remains a multi-variable, nonlinear, and multi-modal problem, has recently gained considerable attention in the simulation and calculation of solar PV systems. Among various parameter extraction techniques, differential evolution (DE) and its variants are envisaged to be pretty effective for parameter extraction of PV models. In this paper, 11 state-of-the-art DE algorithms are comprehensively compared to extract the parameters of different PV models. The performance of each algorithm is evaluated based on the accuracy of solution, convergence speed, and the robustness. Based on the experimental results and analysis of different DE algorithms, the useful insights are concluded, which can guide the improvement of designing more efficient alternative DE methods for solving the PV parameter extraction problems.
关键词： Comparative study,Parameter extraction,Differential evolution,Photovoltaic models
更新于2025-09-19 17:13:59
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Efficient Carrier Transport for AlGaN-Based Deep-UV LEDs With Graded Superlattice p-AlGaN
摘要： This paper studies the optimization problem of topological active net (TAN), which is often seen in image segmentation and shape modeling. A TAN is a topological structure containing many nodes, whose positions must be optimized while a prede?ned topology needs to be maintained. TAN optimization is often time-consuming and even constructing a single solution is hard to do. Such a problem is usually approached by a “best improvement local search” (BILS) algorithm based on deterministic search (DS), which is inef?cient because it spends too much efforts in nonpromising probing. In this paper, we propose the use of micro-differential evolution (DE) to replace DS in BILS for improved directional guidance. The resultant algorithm is termed deBILS. Its micro-population ef?ciently utilizes historical information for potentially promising search directions and hence improves ef?ciency in probing. Results show that deBILS can probe promising neighborhoods for each node of a TAN. Experimental tests verify that deBILS offers substantially higher search speed and solution quality not only than ordinary BILS, but also the genetic algorithm and scatter search algorithm.
关键词： grid deformation,topological active net (TAN),structure optimization,Differential evolution (DE),topological optimization
更新于2025-09-19 17:13:59