Nonlinear THz-Nano Metasurfaces

Extreme terahertz (THz) science and technologies, the next disruptive frontier in nonlinear optics, provide multifaceted capabilities for exploring strong light-matter interactions in a variety of physical systems. However, current techniques involve the need for an extremely high-field free space THz source that is difficult to generate and has limited investigations to a rather weak and linear regime of light-matter interactions. Therefore, new approaches are being sought for the tight confinement of THz waves that can induce nonlinear effects. Here, a nonlinear “tera-nano” metasurface is demonstrated exhibiting extremely large THz nonlinearity and sensitive self-modulation of resonances at moderate incident THz field strengths. A record deep-subwavelength (≈λ/33 000) confinement of strongly enhanced (^≈3200) THz field in a nano-gap (15 nm) exhibits remarkable THz field-tailored nonlinearity. Further, ultrafast injection of photocarriers reveals a competition between nonlinear THz field-induced intervalley scattering and optically driven interband excitations. The results on “tera-nano” metasurfaces enable a novel platform to realize enhanced nonlinear nano/micro composites for field-sensitive extreme THz nonlinear applications without the need for intense THz light sources.     

Nitrate Additives Coordinated with Crown Ether Stabilize Lithium Metal Anodes in Carbonate Electrolyte

Lithium metal anodes (LMAs) are promising for next-generation batteries but have poor compatibility with the widely used carbonate-based electrolytes, which is a major reason for their severe dendrite growth and low Coulombic efficiency (CE). A nitrate additive to the electrolyte is an effective solution, but its low solubility in carbonates is a problem that can be solved using a crown ether, as reported. A rubidium nitrate additive coordinated with 18-crown-6 crown ether stabilizes the LMA in a carbonate electrolyte. The coordination promotes the dissolution of NO₃⁻ ions and helps form a dense solid electrolyte interface that is Li₃N-rich which guides uniform Li deposition. In addition, the Rb (18-crown-6)⁺ complexes are adsorbed on the dendrite tips, shielding them from Li deposition on the dendrite tips. A high CE of 97.1% is achieved with a capacity of 1 mAh cm⁻² in a half cell, much higher than when using the additive-free electrolyte (92.2%). Such an additive is very compatible with a nickel-rich ternary cathode at a high voltage, and the assembled full battery with a cathode material loading up to 10 mg cm⁻² shows an average CE of 99.8% over 200 cycles, indicating a potential for practical use.     

Sustainable 3D Structural Binder for High-Performance Supercapacitor by Biosynthesis Process

Flexible supercapacitors represent an attractive technology for the next generation of wearable consumer electronics as power sources but usually suffer from relatively low energy density. It is highly desired to construct high-performance electrodes for the practical applications of supercapacitors. Here, inspired by the natural structure of the spider web, an elaborate design of binder is reported through a biosynthesis process to construct flexible electrodes with both excellent mechanical properties and electrochemical performance. Through this strategy, a spider-web-inspired 3D structural binder enables large ion-accessible surface area and high packing density of active electrode material as well as efficient ion transport pathways. As a result, a high areal capacitance of 4.62 F cm^-2 and a high areal energy density of 0.18 mW h cm^-2 is achieved in the composite electrodes and symmetric supercapacitors, respectively, demonstrating a promising potential to construct flexible energy storage devices for diverse practical applications.     

Self-Assembled Perovskite Nanoislands on CH3NH3PbI3 Cuboid Single Crystals by Energetic Surface Engineering

Organometal perovskite single crystals have been recognized as a promising platform for high-performance optoelectronic devices, featuring high crystallinity and stability. However, a high trap density and structural nonuniformity at the surface have been major barriers to the progress of single crystal-based optoelectronic devices. Here, the formation of a unique nanoisland structure is reported at the surface of the facet-controlled cuboid MAPbI₃ (MA = CH₃NH₃⁺) single crystals through a cation interdiffusion process enabled by energetically vaporized CsI. The interdiffusion of mobile ions between the bulk and the surface is triggered by thermally activated CsI vapor, which reconstructs the surface that is rich in MA and CsI with reduced dangling bonds. Simultaneously, an array of Cs-Pb-rich nanoislands is constructed on the surface of the MAPbI₃ single crystals. This newly reconstructed nanoisland surface enhances the light absorbance over 50% and increases the charge carrier mobility from 56 to 93 cm² V⁻¹ s⁻¹. As confirmed by Kelvin probe force microscopy, the nanoislands form a gradient band bending that prevents recombination of excess carriers, and thus, enhances lateral carrier transport properties. This unique engineering of the single crystal surface provides a pathway towards developing high-quality perovskite single-crystal surface for optoelectronic applications.     

Efficiency Breakthrough of Fluorescence OLEDs by the Strategic Management of “Hot Excitons” at Highly Lying Excitation Triplet Energy Levels

Aggregation-induced emission (AIE) and hybridized local and charge-transfer (HLCT) materials are two kinds of promising electroluminescence systems for the fabrication of high-efficiency organic light-emitting diodes (OLEDs) by harnessing “hot excitons” at the high-lying triplet exciton states (T_n, n ≥ 2). Nonetheless, the efficiency of the resulting OLEDs did not meet expectations due to the possible loss of T_n→T_n−1. Herein, experimental results and theoretical calculations demonstrate the “hot exciton” process between the high-lying triplet state T₃ and the lowest excited singlet state S₁ in an AIE material 4⁗-(diphenylamino)-2″,5″-diphenyl-[1,1″:4′,1″:4″,1′″:4′″,1⁗-quinquephenyl]-4-carbonitrile (TPB-PAPC) and it is found that the Förster resonance energy transfer (FRET) between two molecules can facilitate the “hot exciton” process and inhibit the T₃→T₂ loss by doping a blue fluorescent emitter in TPB-PAPC. Finally, the doped TPB-PAPC blue OLEDs achieve a maximum external quantum efficiency (EQE_max) of 9.0% with a small efficiency roll-off. Furthermore, doping the blue fluorescent emitter in a HLCT material 2-(4-(10-(3-(9H-carbazol-9-yl)phenyl)anthracen-9-yl)phenyl)-1-phenyl-1H-phenanthro[9,10-d] imidazole (PAC) is used as the emission layer, and the resulting blue OLEDs exhibit an EQE_max of 17.4%, realizing the efficiency breakthrough of blue fluorescence OLEDs. This work establishes a physical insight in the design of high-performance “hot exciton” molecules and the fabrication of high-performance blue fluorescence OLEDs.     

Tr-SLDA:一种面向交叉领域的迁移主题模型

当目标领域缺少足够多的标注数据时,迁移学习利用相关源领域的标注数据,辅助提升目标域的学习性能,但是目标域与源域的数据通常不满足独立同分布,容易导致"负迁移"问题.本文在有监督主题模型(Supervised LDA,SLDA)的基础上,融合迁移学习方法提出一种共享主题知识的迁移主题模型(Transfer SLDA,Tr-...     

面向新工科非电类理工科专业的电工学系列课程教学体系改革与探索

电工学系列课程是非电类理工科专业的重要工程基础课程,其教学方案和效果与新工科卓越工程人才的培养质量直接相关.本文在新工科建设的指导思想下,对国内外非电类理工科专业电工学系列课程现状进行调研,在分析非电类理工科专业学生实际需求的基础上,构建与研究非电类理工科专业电工学系列课程建设方案和教学基本要求,以促进新型工程技术人才的培养,为新工科的建设奠定坚实的实践基础.     

军队院校网络教学模式的探索

介绍了军队院校网络教学水平现状,提出了基于军队院校进行网络课程建设的规划和教学组织方法,并针对军校学员的教学模式进行了探讨。     

一个应用于数字音频的高性能、低功耗ΣΔ模数转换器

本文介绍了一个应用于18位高端音频的ΣΔ模数转换器(ADC)。它包括一个2-1级联结构的ΣΔ调制器和一个数字抽取滤波器。在系统设计、电路实现和版图设计的过程中采取了许多优化措施,包括：选择了一个能够实现高过载水平的调制器结构并对其系数进行优化,实现了一个高能效的A/AB 类跨导放大器和一个面积和功耗优化的多级抽取滤波器。模数转换器在中芯国际0.18μm 混合信号CMOS 工艺中流片。测试结果表明在22.05 KHz带宽内,信噪失真比和动态范围分别达到91dB和94dB,而芯片面积为2.1 mm2,其中模拟部分仅消耗2.1mA静态电流。     

基于电力线载波通信的城市灯饰控制系统

介绍了城市灯饰控制系统的组成、工作原理和关键技术。基于无线接力和电力栽波通信技术的城市灯饰控制系统,通过对监控中心监控软件系统的操作,可实现城市灯饰的智能管理控制。电力线载波通信模块设计中采用意法半导体（ST）设计生产的新型电力线收发芯片ST7540,较好地解决了低压电力线载波传输中的干扰问题,稳定的试验数据和成功的小范围适用,表明本系统具有良好的应用前景。