基于能带调制模型的高压增强型AlGaN/GaN HFET器件

提出了一种能带调制模型,通过在异质结界面处引入负离子电荷(如氟离子)调制异质结处的局部能带分布,实现了对异质结界面处的高密度2DEG的改变。基于能带调制模型,提出了一种复合调制沟道AlGaN/GaNHFET器件。通过在增强型沟道调制区和RESURF调制区分别引入不同剂量的负离子,不仅实现了增强型器件,而且可以降低尖峰电场,优化异质结电场分布,提高器件击穿电压。通过器件仿真软件对其器件工作原理进行了模拟分析,并通过实验结果表明,其器件品质因子FOM由传统器件的4.8MW.cm-2提高到26.7MW.cm-2。     

Subjective Listening Experiments on a Front and Rear Array‐Based WFS System

Wave field synthesis (WFS) has been gathering more and more attention recently due to its ability to perfectly reproduce an original sound field. However, to realize theoretically perfect WFS, a four‐sided loudspeaker array that encloses the listener is required. However, it is difficult to build such a system except in large listening spaces, such as a theater or concert hall. In other words, if the listening space is a home, installing a side loudspeaker array is impractical. If the two side walls located to the left and right of the listener can be omitted, a setup using only front and rear loudspeaker arrays may be a solution. In this letter, we present a subjective listening experiment of sound localization/distance based on a WFS using a front and rear loudspeaker array system which is conducted on two listening points and shows average localization errors of 6.1° and 9.18°, while the average distance errors are –27% (0.5 m) and –29% (0.6 m), respectively.     

激光烧结Si／Fe混合粉末材料的温度场有限元模拟

利用ANSYS工具建立了选择性激光烧结热电功能材料β-FeSi2的三维瞬态温度场有限元模型,模型中考虑了混合材料热物性参数随温度与孔隙率的变化和材料相变过程对温度场的影响。系统分析了选择性激光烧结二元粉末内部温度场随时间和空间的变化规律,通过该有限元模型可以分析二元粉末激光烧结过程中激光热能在粉床内部的传输规律。模拟结果表明,随烧结深度增加,粉床内部温度和温度梯度迅速衰减,粉床内部温度场在深度方向呈漏斗状梯度分布,粉层内部热影响区域最深的位置滞后于激光束中心。在已烧结区域,粉层内部存在一个均匀分布的高温体积区间。对此粉层区域温度的研究将为实验中控制烧结材料相变过程与性能提供依据。     

All‐Carbon Nanotube‐Based Flexible Field‐Emission Devices: From Cathode to Anode

The fabrication of a flexible field‐emission device (FED) using single‐walled carbon nanotube (SWNT) network films as the conducting electrodes (anode and cathode) and thin multi‐walled CNT/TEOS hybrid films as the emitters is reported. P‐type doping with gold ions and passivation with tetraethylorthosilicate (TEOS) made the SWNT network film highly conductive and environmentally stable, and hence a good alternative to conventional indium tin oxide electrodes. CNT/TEOS hybrid emitters showed high current density, low turn‐on field, and long‐term emission stability, compared with CNT emitters; these characteristics can be attributed to the TEOS sol, acting both as a protective layer surrounding the nanotube tip, and as an adhesive layer enhancing the nanotube adhesion to the substrate. All‐CNT‐based flexible FEDs fabricated by this approach showed high flexibility in field emission characteristics and extremely bright electron emission patterns.     

Anisotropy of Charge Transport in a Uniaxially Aligned and Chain‐Extended,High‐Mobility,Conjugated Polymer Semiconductor

Charge transport in the ribbon phase of poly(2,5‐bis(3‐alkylthiophen‐2‐yl)thieno[3,2‐b]thiophene) (PBTTT)—one of the most highly ordered, chain‐extended crystalline microstructures available in a conjugated polymer semiconductor—is studied. Ribbon‐phase PBTTT has previously been found not to exhibit high carrier mobilities, but it is shown here that field‐effect mobilities depend strongly on the device architecture and active interface. When devices are constructed such that the ribbon‐phase films are in contact with either a polymer gate dielectric or an SiO₂ gate dielectric modified by a hydrophobic, self‐assembled monolayer, high mobilities of up to 0.4 cm² V^?1 s^?1 can be achieved, which is comparable to those observed previously in terrace‐phase PBTTT. In uniaxially aligned, zone‐cast films of ribbon‐phase PBTTT the mobility anisotropy is measured for transport both parallel and perpendicular to the polymer chain direction. The mobility anisotropy is relatively small, with the mobility along the polymer chain direction being higher by a factor of 3–5, consistent with the grain size encountered in the two transport directions.     

基于MODBUS现场总线的滚塑设备控制系统

滚塑生产是塑料制品的主要生产方式。现有的滚塑设备已成为制约企业发展的关键因素。研制以PLC为核心控制元件、基于MODBUS协议的控制系统已迫在眉捷。着重介绍基于MODBUS现场总线的滚塑设备控制系统,它由上位机、PLC、变频器组成一个数字通信网络,可方便地实现对现场各参数的修改,将系统运行中出现的故障进行分级处理,并将各参数进行记录。将现场总线应用到滚塑设备的控制系统之后,既可以提高设备的智能化程度又能提高生产效率,同时增强了设备运行的可靠性、稳定性,使产品质量大大提高。利用现场总线PLC,PLD等现代化数控网络技术对滚塑设备进行革新和改造,显著提高现有设备的智能化程度。     

光子晶体光纤数值孔径测试的一种新方法

应用光谱仪测量光子晶体光纤(PCF)的数值孔径(NA),不仅克服了传统法只能测量几个固定波长下NA的局限性,还可以对PCF与波长有关的模场面积、截止波长等参数进行研究。实验测量结果与理论计算值进行了比较,取得了满意结果。由测得的NA计算PCF的模场面积,与多极法模拟结果一致性较好。给出了NA与截止波长的关系。     

Hierarchically Structured Self‐Healing Sensors with Tunable Positive/Negative Piezoresistivity

It is a challenge to manufacture flexible sensors that possess easily distinguishable biomotion signals, strong response reliability, and excellent self‐healing capability. Herein, a self‐healing sensor with tunable positive/negative piezoresistivity is designed by the construction of hierarchical structure connected through supramolecular metal–ligand coordination bonds. The developed sensors can be integrated with the human body to detect multiple tiny signals, such as pronunciation, coughing, and deep breathing. Interestingly, the nanostructured elastomer sensor with and without a flexible yarn electrode shows negative and positive current signals, respectively, making it easy to be identify. Furthermore, it exhibits very fast (2 min), autonomous, and repeatable self‐healing ability with high‐healing efficiency (88.6% after the third healing process). The healed samples still possess flexibility, high sensitivity, and accurate detection capability, even after bending over 10 000 cycles. The excellent biomimetic self‐healing performance combined with the tunable piezoresistivity make it promising for next‐generation wearable electronics.     

Alternating Magnetic Field-Enhanced Triboelectric Nanogenerator for Low-Speed Flow Energy Harvesting

Low-speed flow energy, such as breezes and rivers, which are abundant in smart agriculture and smart cities, faces significant challenges in efficient harvesting as an untapped sustainable energy source. This study proposes an alternating magnetic field-enhanced triboelectric nanogenerator (AMF-TENG) for low-speed flow energy harvesting, and demonstrates its feasibility through experimental results. AMF-TENG's minimum cut-in speed is 1 m s⁻¹, thereby greatly expanding its wind energy harvesting range. When the wind speed is 1–5 m s⁻¹, the open-circuit voltage (V_OC) is 20.9–179.3 V. The peak power is 0.68 mW at 5 m s⁻¹. In a durability test of 100 K cycles, the V_OC decreases from 188.4 to 174.2 V but remain at 92.5% of the initial value. furthermore, the AMF-TENG can harvest low-speed flow energy from the natural environment to power temperature and humidity sensors and wireless light intensity sensor in smart agriculture. This study provides a promising method for low-speed flow energy harvesting in distributed applications.     

基于FPGA的RS(255,239)编译码器

编码是一种具有较强纠错能力的多进制BCH编码,其既可纠正随机错误,又可纠正突发错误。RS编译码器广泛应用于通信和存储系统,为解决高速存储器中数据可靠性的问题,文中提出了RS编码的实现方法,并对编码进行了时序仿真。仿真结果表明,该译码器可实现良好的纠错功能。