Adaptive prescribed time control for quadrotor formation with stochastic links failure

The formation control for multiple quadrotors subject to maintaining the formation configuration and collision avoidance in the situation of stochastic links failure is investigated in this paper. First, the distributed formation controller is designed, the position controller is developed to manage the desired formation of position, and the attitude controller is developed to control the translation and rotation movements of the quadrotor. Then, in order to avoid the collisions between multiple quadrotors and the obstacles, a potential energy function method is introduced into the quadrotor formation control combined with the nest adaptive control. Inspired by the design of event trigger controller, a communication compensation controller is designed to ensure the stability of quadrotor formation under the condition of random communication interruption and recovery. Moreover, a prescribed time function is designed, which means the convergence time of the formation system can be set in advance. The prescribed time stability of the formation control system is proved by Lyapunov theory. Finally, the simulation results verify the effectiveness and superiority of this method.     

A heterogeneous multi-attribute case retrieval method based on neutrosophic sets and TODIM for emergency situations

Applied Intelligence - Heterogeneous multi-attribute case retrieval is a crucial step in generating emergency alternatives during the course of emergency decision making (EDM) by referring to...     

船舶舱室正压排烟方案优化及仿真分析

本文主要针对船舶模拟舱室的正压排烟进行研究,以期为现代船舶的消防建设提供参考,将烟控区抽离建模如下文图一,设计正交排烟方案,由实验结果的极差分析得到最优的正压排烟方案即:风速15m/s,出口开度1.2m,进口开度0.3m。针对最优方案,由Fluent仿真分析得到:烟气聚集的地方,温度要高于周围,旋涡的存在导致烟气的滞留,说明针对烟气流动路径的研究将有利于排烟效果的改善。     

Synergistic effects of micro-/nano-fillers on conductive and electromagnetic shielding properties of polypropylene nanocomposites

This study presents the synergistic effects of graphene nanosheets (GNSs) and carbon fibers (CFs) additions on the electrical and electromagnetic shielding properties of GNS/CF/polypropylene (PP) composites. These composites were fabricated by the melt blending of different ratios of GNSs and CFs (20:0, 15:5, 10:10, 5:15 and 0:20 wt/wt%) into a PP polymer matrix using a Brabender mixer. Besides, the chemical and crystalline structures and the thermal stability of the resultant GNS/CF/PP composites were characterized by Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD) and thermogravimetric analysis (TGA). FT-IR and XRD showed that with the addition of GNSs content, transmittances at 1373.4?cm^?1 and 1454.4?cm^?1 became smaller and the characteristic peak at 26.82° became stronger. TGA showed that the GNS/CF/PP composite can be used at high temperature below 456°C. Blending 10?wt% CFs and 10?wt% GNSs into the PP polymer resulted in excellent conductivity (0.397 S/cm), which indicated the occurrence of the critical percolation threshold phenomenon, and also reached the maximum electromagnetic shielding effectiveness (EMSE) of 20?dB at 1.28–2.00?GHz. Laminated with five layers of composites, its EMSE achieved 25–38?dB at 0.3–3.0?GHz, corresponding to blocking of 94.38–98.74% electromagnetic waves.     

Monitoring the Dynamic Process of Formation of Plasmonic Molecular Junctions during Single Nanoparticle Collisions

The capability to study the dynamic formation of plasmonic molecular junction is of fundamental importance, and it will provide new insights into molecular electronics/plasmonics, single‐entity electrochemistry, and nanooptoelectronics. Here, a facile method to form plasmonic molecular junctions is reported by utilizing single gold nanoparticle (NP) collision events at a highly curved gold nanoelectrode modified with a self‐assembled monolayer. By using time‐resolved electrochemical current measurement and surface‐enhanced Raman scattering spectroscopy, the current changes and the evolution of interfacial chemical bonding are successfully observed in the newly formed molecular tunnel junctions during and after the gold NP “hit‐n‐stay” and “hit‐n‐run” collision events. The results lead to an in‐depth understanding of the single NP motion and the associated molecular level changes during the formation of the plasmonic molecular junctions in a single NP collision event. This method also provides a new platform to study molecular changes at the single molecule level during electron transport in a dynamic molecular tunnel junction.     

A Two‐Stage Annealing Strategy for Crystallization Control of CH3NH3PbI3 Films toward Highly Reproducible Perovskite Solar Cells

The solvent‐engineering method is widely used to fabricate top‐performing perovskite solar cells, which, however, usually exhibit inferior reproducibility. Herein, a two‐stage annealing (TSA) strategy is demonstrated for processing of perovskite films, namely, annealing the intermediate phase at 60 °C for the first stage then at 100 °C for the second stage. Compared to conventional direct annealing temperature (DHA) at 100 °C, using this strategy, MAPbI₃ films become more controllable, leading to superior film uniformity and device reproducibility with the champion device efficiency reaching 19.8%. More specifically, the coefficient of variation of efficiency for 49 cells is reduced to 5.9%, compared to 9.8% for that using DHA. The TSA process is carefully studied using Fourier transform infrared spectroscopy, X‐ray diffraction, and UV–vis absorption spectroscopy. It is found that in comparison with DHA the formation of hydrogen bonding and crystallization of perovskite are much slower and can be better controlled when using TSA. The improvements in film uniformity and device reproducibility are attributed to: 1) controllable MAPbI₃ crystal growth stemming from the progressive formation of hydrogen bonding between methylammonium and halide; 2) suppression of intermediate phase film dewetting, which is believed to be due to its decreased mobility at the initial low‐temperature annealing stage.     

In-situ synthesis of TiO2 nanostructures on Ti foil for enhanced and stable photocatalytic performance

TiO_2 nanostructures with strong interfacial adhesion and diverse morphologies have been in-situ grown on Ti foil substrate through a multiple-step method based on conventional plasma electrolytic oxidation(PEO) technology, hydrothermal reaction and ion exchange process. The PEO process is critical to the formation of TiO_2 seeding layer for the nucleation of Na_2Ti_3O_7 and H_2Ti_3O_7 mediates that are strongly attached to the Ti foil. An ion exchange reaction can finally lead to the formation of H_2Ti_3O_7 nanostructures with diverse morphologies and the calcination process can turn the H_2Ti_3O_7 nanostructures into TiO_2 nanostructures with enhanced crystallinity. The morphology of the TiO_2 nanostructures including nanoparticles(NP), nanowhiskers(NWK), nanowires(NW) and nanosheets(NS) can be easily tailored by controlling the NaOH concentration and reaction time during hydrothermal process. The morphology, composition and optical properties of TiO_2 photocatalysts were analyzed using scanning electron microscope(SEM), X-ray diffraction(XRD), photoluminescence(PL) spectroscopy and UV–vis absorption spectrum. Photocatalytic tests indicate that the TiO_2 nanosheets calcined at 500?C show good crystallization and the best capability of decomposing organic pollutants. The decoration of Ag cocatalyst can further improve the photocatalytic performance of the TiO_2 nanosheets as a result of the enhanced charger separation efficiency. Cyclic photocatalytic test using TiO_2 nanostructures grown on Ti foil substrate demonstrates the superior stability in the photodegradation of organic pollutant, suggesting the promising potential of in-situ growth technology for industrial application.     

Large capacitance and fast polarization response of thin electrolyte dielectrics by spin coating for two-dimensional MoS2 devices

Nano Research - A spin-coating method was applied to obtain thinner and smoother PEO/LiClO4 polymer electrolyte films (EFs) with a lower level of crystallization than those obtained using a...