基于表面势的HEMT模型分析

将表面势的概念引入GaAs高电子迁移率晶体管器件结构,以建立可精确描述HEMT器件输入/出特性的新模型。通过分析最基本的HEMT结构,参考Si基MOSFET中Pao-sah模型的分析方法,对沟道电荷利用泊松方程表述,并结合能带电压关系,建立HEMT器件中表面势(Φ_s)对于栅压(V_(GS))的关系。基于上述分析计算了沟道中电子的饱和点。根据推导所得方程,模型计算得到的某具体器件沟道面电荷密度(n_s)-栅压(V_(GS))关系曲线和基于T-CAD工具仿真结果在线性区得到很好的吻合。     

含有屈曲约束支撑框架的振动台试验研究

通过对含有屈曲约束支撑的框架进行振动台试验,研究了屈曲约束支撑对结构地震反应的减震效果。选用3条天然波和1条人工波进行加载,记录了模型的加速度反应,分析了BRB在试验中的力学性能,并与理论计算值进行了对比,研究了台面输入加速度为0.6g和1.0g时框架底层BRB的滞回曲线。探讨了不同台面输入下输入能量在模型中的分布情况。试验及研究结果表明,当台面输入加速度小于0.6g时,屈曲约束支撑可以为结构提供稳定的侧向刚度;当台面输入加速度大于0.6g时,屈曲约束支撑通过自身塑性变形来吸收能量;当台面输入加速度为1.0g时,屈曲约束支撑可以吸收台面输入的20%~40%的能量。     

控制超高层建筑桩筏基础筏板弯矩的方法

为保证超高层建筑桩筏基础的筏板弯矩设计能够控制在安全范围内,采用相对弯曲计算筏板弯矩法(简称反算弯矩法)与共同作用理论的解析-数值解混合法(简称共同作用混合法)分别对金茂大厦、上海环球金融中心两个实例进行分析。根据共同作用混合法计算上海中心大厦的地基变形,用以计算相对弯曲,求得相应弯矩,同时,分别采用共同作用混合法和共同作用数值解-迭代法(简称共同作用迭代法)计算上海中心大厦筏板弯矩并进行比较。利用上述计算的结果,分析上海中心大厦的筏板弯矩,确定控制其筏板弯矩的安全范围。     

无锡新区科技交流中心钢屋盖施工技术

无锡新区科技交流中心钢屋盖为梅花形,采用双曲桁架与单层网壳构成的组合结构,具有跨度大、弧形杆件多、连接节点形式复杂等特点。针对工程施工难点,采取合理的施工技术:三维可视化建模技术用于加工形体复杂的铸钢件;六维数控相贯线切割技术用于屋盖钢管的切割;计算机放样技术应用于双曲桁架的拼装;临时改变传力路径的加固方法用以实现桁架吊装安全;合理制定桁架和网壳的吊装流程以减少安装应力;恰当的测量方法应用于桁架拼装和屋盖吊装的全过程。结果表明,制作和安装精度皆符合国家规范要求,并且保证了施工安全性。     

Graphene substrates promote adherence of human osteoblasts and mesenchymal stromal cells

The biocompatibility of large single layer graphene produced by chemical vapour deposition was investigated using human osteoblasts and mesenchymal stromal cells. The study was focused on cellular adhesion, morphology and the ability to proliferate on graphene substrates. It was found that both of the cell types which were tested adhered and proliferated better when cultured on graphene films than on a SiO₂ substrate.     

Effect of elevated temperatures on geopolymer paste, mortar and concrete

Geopolymers are generally believed to provide good fire resistance due to their ceramic-like properties. Previous experimental studies on geopolymer under elevated temperatures have mainly focused on metakaolin-based geopolymers. This paper presents the results of a study on the effect of elevated temperature on geopolymer paste, mortar and concrete made using fly ash as a precursor. The geopolymer was synthesized with sodium silicate and potassium hydroxide solutions. Various experimental parameters have been examined such as specimen sizing, aggregate sizing, aggregate type and superplasticizer type. The study identifies specimen size and aggregate size as the two main factors that govern geopolymer behavior at elevated temperatures (800 °C). Aggregate sizes larger than 10 mm resulted in good strength performances in both ambient and elevated temperatures. Strength loss in geopolymer concrete at elevated temperatures is attributed to the thermal mismatch between the geopolymer matrix and the aggregates.     

基于DBR结构自脉动激光器的波长及频率可变光微波源

首次报道了基于DBR结构自脉动激光器的波长及频率可变光微波源。该微波源可以或得1.87GHz至21.81GHz的微波信号同时可以获得1536.28nm至1538.73nm的波长调谐。     

The promotional effect of Cr on catalytic activity of Pt/ZSM-35 for H2-SCR in excess oxygen

Selective catalytic reduction of NO by hydrogen was studied over Cr modified Pt/ZSM-35 catalysts. The preparation process greatly influenced catalytic activity and sample prepared by co-impregnation method exhibits the best activity. In situ DRIFT studies revealed that on Pt–Cr/ZSM-35, (1) new Pt-NO^δ+ and NO species adsorbed on Pt were detected upon NO + O₂ adsorption; (2) much more ammonia species were formed under reaction condition. Cr addition not only enhanced the adsorption of NO_x but also promoted the formation of surface NH₄⁺ species, which should be the origin of promotional effect of Cr on Pt/ZSM-35 for H₂-SCR reaction.     

摩擦过程多源信息采集系统设计研究

为获取摩擦过程中产生的多源信息,基于环境设计理论分析摩擦学试验研究的现状和需求,构建摩擦过程多源信息采集系统的递归对象模型,通过识别关键冲突并寻求解决方案,实现系统的整体方案设计。通过多传感器部署和LabVIEW软件开发,研制一种基于通用摩擦磨损试验机的摩擦过程多源信息采集系统,实现摩擦过程中的振动、声音、声压等多源信息的实时采集、存储和展示。将系统进一步集成化并基于Unity 3D构建摩擦磨损试验机的数字孪生虚拟实体,同时为便于多源信息的后续利用,提出相应的信号预处理方法。通过试验验证该系统满足摩擦试验中多源信息的采集需求,能够为后续开展多源信息融合、多学科信息关联映射提供数据基础,也为实现基于摩擦学衍生量的摩擦学状态监测提供数据基础。     

Erase voltage impact on 0.18μm triple self-aligned split-gate flash memory endurance

The erase voltage impact on the 0.18μm triple self-aligned split-gate flash endurance is studied.An optimized erase voltage is necessary in order to achieve the best endurance.A lower erase voltage can cause more cell current degradation by increasing its sensitivity to the floating gate voltage drop,which is induced by tunnel oxide charge trapping during program/erase cycling.A higher erase voltage also aggravates the endurance degradation by introducing select gate oxide charge trapping.A progressive erase voltage method is proposed and demonstrated to better balance the two degradation mechanisms and thus further improve endurance performance.