柴油机喷油器喷孔积碳对喷雾影响研究

在定容弹中进行了柴油机喷油器冷态喷雾特性试验,对比分析了积碳喷油器和新喷油器在不同喷射条件下的喷雾贯穿距和喷雾锥角。试验结果表明：喷油器喷孔积碳后,喷雾贯穿距和喷雾锥角减小,喷射初期差距较大,喷射后期差距缩小;喷射压力越大,喷雾贯穿距和喷雾锥角下降越明显。利用光学显微镜观察喷孔出口积碳发现,喷孔出口积碳分布在喷孔外沿,改变了原有的出口结构。利用流体体积方法,对喷孔内部流动进行数值仿真计算,分析了孔内积碳、出口积碳以及喷孔增长对喷孔内部流动的影响。计算结果表明：孔内积碳、出口积碳、喷孔增长导致喷孔内部空化效应减弱,出口质量流量、速度、湍动能下降,油束雾化质量变差,出口积碳影响作用更大。     

基于Wi-Fi即时定位与映射像素模板匹配的室内运动地图构建与定位

传统指纹定位方法由于建库人力时间开销大、系统通用性不强约束着指纹定位系统的推广,为了解决该问题同时结合即时定位与映射(SLAM)技术的优势,该文提出一种新的Wi-Fi/微机电系统(MEMS)融合室内运动地图构建与定位方法。首先利用行人航迹推算(PDR)、最小描述长度(MDL)原则和基于密度的空间聚类算法(DBSCAN)对众包运动轨迹进行预处理,提出基于轨迹主路径的运动地图构建方法。之后提出基于像素模板的地图匹配方法获取地图的绝对位置,并采用抗差扩展卡尔曼滤波(EKF)对目标位置进行最优估计。实验结果表明,所提聚类方法可以准确构建各区域运动地图,在少量的人力时间开销下实现较高的定位精度。     

基于传输中断概率的认知无线电系统性能分析

如何设计最优的频谱感知与传输框架是认知无线电技术的重要环节。考虑频谱接入过程中数据传输中断对认知网络性能影响的问题,提出了一种新的基于传输中断概率的频谱感知与传输模型,联合优化频谱感知和数据传输两个阶段,将问题建模为对主用户的干扰量约束条件下的非凸优问题,以最大化认知网络吞吐量为目标联合优化感知时间、传输速率,并通过数值计算方法对其进行求解与仿真。数值分析表明,引入传输中断概率后,在满足上述约束条件的同时,在保护主用户和认知网络吞吐量、传输时延之间有了更好的权衡。     

Effects of vapor-annealed gate dielectric on the properties of zinc tin oxide transparent thin film transistors

We investigated the effects of vapor-annealed gate dielectrics on the mobility, threshold voltage, and other characteristics of bottom gate zinc tin oxide (ZTO) transparent thin film transistors (TTFTs). Here, Al₂O₃ films coated on dry oxidized Si wafers were annealed in a water vapor atmosphere before ZTO deposition and used as TTFT gate dielectrics. The vapor-annealed ZTO TTFTs exhibited 50% higher mobility than those that were not vapor annealed. This improvement in mobility is ascribed to the hydrogen passivation in the amorphous ZTO films     

Designing a Stable Cathode with Multiple Layers to Improve the Operational Lifetime of Polymer Light‐Emitting Diodes

The short device lifetime of blue polymer light‐emitting diodes (PLEDs) is still a bottleneck for commercialization of self‐emissive full‐color displays. Since the cathode in the device has a dominant influence on the device lifetime, a systematic design of the cathode structure is necessary. The operational lifetime of blue PLEDs can be greatly improved by introducing a three‐layer (BaF₂/Ca/Al) cathode compared with conventional two‐layer cathodes (BaF₂/Al and Ba/Al). Therefore, the roles of the BaF₂ and Ca layers in terms of electron injection, luminous efficiency, and device lifetime are here investigated. For efficient electron injection, the BaF₂ layer should be deposited to the thickness of at least one monolayer (～3 nm). However, it is found that the device lifetime does not show a strong relation with the electron injection or luminous efficiency. In order to prolong the device lifetime, sufficient reaction between BaF₂ and the overlying Ca layer should take place during the deposition where the thickness of each layer is around that of a monolayer.     

雷达目标空频域瞬态极化特性及其在几何结构反演中的应用

该文针对高分辨全极化成像雷达体制,研究了雷达目标的空频域瞬态极化特性及其在目标几何结构反演中的应用.给出了空频域瞬态极化特性的表征及获取方法,将已有瞬态极化理论拓广至空频域,并对典型散射结构的空频域瞬态极化特性进行对比分析.作为应用,提出基于空频域瞬态极化特性分析的雷达目标几何结构反演方法,该方法通过揭示空频域瞬态极化特征与散射结构类型间的对应关系,可以克服传统反演的模糊性和局限性,实现更为准确和可信的反演.基于暗室测量数据验证了该方法的有效性.     

An Investigation on the Coupled Thermal–Mechanical–Electrical Response of Automobile Thermoelectric Materials and Devices

Thermoelectric (TE) materials, which can directly convert heat to electrical energy, possess wide application potential for power generation from waste heat. As TE devices in vehicle exhaust power generation systems work in the long term in a service environment with coupled thermal–mechanical–electrical conditions, the reliability of their mechanical strength and conversion efficiency is an important issue for their commercial application. Based on semiconductor TE devices wih multiple p–n couples and the working environment of a vehicle exhaust power generation system, the service conditions of the TE devices are simulated by using the finite-element method. The working temperature on the hot side is set according to experimental measurements, and two cooling methods, i.e., an independent and shared water tank, are adopted on the cold side. The conversion efficiency and thermal stresses of the TE devices are calculated and discussed. Numerical results are obtained, and the mechanism of the influence on the conversion efficiency and mechanical properties of the TE materials is revealed, aiming to provide theoretical guidance for optimization of the design and commercial application of vehicle TE devices.     

国产双辊热轧机

国产双辊热轧机的性能优良,工作可靠;轧制的非织造布强力高,柔软度和手感好,达到了国外同类产品的质量指标,得到用户的认可和好评.该机适用于纺粘法聚丙烯非织造布和聚酯短纤维热轧非织造布的生产。本文介绍了该机的工作原理、结构特点、使用情况及其取得的经济效益。