多晶硅薄膜的高温压阻效应

利用LPCVD制备重掺杂多晶硅薄膜,在0～560℃温度范围内对薄膜的压阻效应进行研究,同时对多晶硅薄膜应变系数随温度的变化,以及薄膜的淀积温度与薄膜厚度对应变系数的影响进行了相关的实验研究.结果表明,利用多晶硅材料制作的压敏电阻,其最高工作温度可以达到560℃以上.     

基于无线传感器网络的智能灌溉系统研究

针对我国水资源紧缺以及农田节水灌溉的需求,根据现有的农田灌溉装备条件,应用领域作物、土壤、水源布点等情况,分析了目前实现精确农业亟待解决的关键技术问题,提出一套采用无线传感器网络技术、适合大面积农田智能灌溉控制方法。分析结果表明,该系统通过无线传感技术完成智能化灌溉,可很好地实现节水。且该系统工作稳定,具有一定的推广应用价值。     

国产4H-SiC SI衬底MESFET外延生长及器件研制

以国产衬底实现SiC加工工艺链为目标,采用国产4H-SiC半绝缘衬底材料外延得到4H-SiC MESFET结构材料.外延片XRD半宽43.2 arcs,方块电阻121点均匀性18.39%,随后制备出的具有直流特性的4H-SiC MESFET器件管芯,器件总栅宽250 μm,饱和电流密度680 mA/mm,跨导约为20 mS/mm,在20 V下的栅漏截止漏电为10 μA,2 mA下栅漏击穿电压为80 V.比例占总数的70%以上.初步实现从衬底到外延,进而实现器件的完整工艺链,为进一步的工艺循环打下良好基础.     

塑封双极型功率晶体管的失效与案例分析

由于其自身的结构与封装形式,塑封双极型功率管存在很多可靠性问题.介绍了塑封双极型功率晶体管可靠性问题及失效机理,包括封装缺陷、粘结失效以及由于温度变化而引起的热应力失效和由于吸入潮气而导致的腐蚀失效.通过剖析一晶体管的失效机理,给出了对此类晶体管失效分析的方法和思路.讨论了晶体管存在异物、芯片粘结失效和热应力失效等失效模式.     

蓝牙跳频通信系统仿真设计

蓝牙通信技术因建立灵活、成本低、功耗低的特点而得到广泛应用。在介绍蓝牙跳频通信技术原理基础上,建立蓝牙跳频通信系统结构组成框图。应用Simulink对系统进行仿真,解释各模块的作用,列出具体的模块参数设置和参数设置的依据。仿真分析结果表明,蓝牙跳频通信系统的抗干扰性能受信道信噪比影响,因采用分组传输的方式,连续相位调制方式及跳频技术,蓝牙跳频系统具有较强的抗干扰能力。     

载荷谱飞行实测振动环境谱数据处理研究

通过开展飞机振动环境谱的飞行实测,获取飞机设备舱、管路、部分飞机结构等振动环境情况,经过数据处理获取能够反映飞机实际使用下的振动环境数据,给出了典型任务剖面的功率谱密度处理结果,为飞机耐久性/损伤容限优化设计提供依据,进一步提高飞行的安全性和可靠性。     

瑞利测风激光雷达接收机校准

介绍了直接探测瑞利测风激光雷达工作及风速反演的原理,说明了激光雷达接收机的内部结构及工作情况。为修正雷达接收机中分光片分束比、单光子计数器探测率等参数与设计值的偏差所导致的风速测量误差,提出了随光强变化比较两信号通道的计数值的接收机校准方案。实验测得了校准系数随信号通道信号强度的变化关系。在弱光下该系统两信号通道性能差异小于25%。在当前系统的标准具透过率条件和对称的风场扫描合成方式下,接收机校准只对系统透过率曲线和径向风速的测量有较大影响,对合成风场没有影响。     

基于图模型的小尺寸飞行器地面试验中位姿估计方法

在多飞行器地面试验位姿估计中,由于跟踪算法导致的跟踪轨迹不连续会使得位姿估计产生累积误差,为了实现位姿的精确估计,提出了一种基于图模型的全局位姿估计非线性优化方法。首先,建立了一个飞行器地面视觉位姿估计系统。然后根据飞行器上特征点的数目提出了一种向量交叉式的飞行器位姿解算方法,求解得到数据已关联飞行器位姿估计值。利用中介坐标系法求解得到轨迹段初始位姿节点在测量坐标系下的值,最后,在图模型基础上下,对整个量测过程中飞行器的位姿估计结果进行非线性全局优化减小线性算法的累积误差,并通过仿真与实际实验对飞行器位姿估计算法的可行性与精度进行验证。实验结果表明:在测量范围为6 000 mm×6 000 mm×3 000 mm的范围内,飞行器尺寸约为400 mm,特征点三维定位精度为2.9 mm的条件下,基于非线性优化的飞行器位姿估计算法的理论精度分别可达0.5°(3σ)与3 mm (3σ),实际绝对测量精度分别可达1.3°(3σ)与4 mm (3σ),基本满足地面试验对多飞行器编队算法开发以及制导控制系统性能长时间评估稳定可靠、精度高、抗干扰能力强等要求。     

Packet‐level‐based traffic aggregation to optimize NDN content delivery

In recent years, named data networking (NDN) has been accepted as the most popular future paradigm and attracted much attention, of which the routing model contains interest forwarding and content delivery. However, interest forwarding is far from the bottleneck of routing optimization; instead, the study on content delivery can greatly promote routing performance. Although many proposals on content delivery have been investigated, they have not considered packet‐level caching and deep traffic aggregation, which goes against the performance optimization of content delivery. In this paper, we propose a packet‐level‐based traffic aggregation (PLTA) scheme to optimize NDN content delivery. At first, the packet format is devised, and data plane development kit (DPDK) is used to ensure same size for each packet. Then, the whole delivery scheme with traffic aggregation consideration is presented. The simulation is driven by the real YouTube dataset over Deltacom, NSFNET, and CERNET topologies, and the experimental results demonstrate that the proposed PLTA has better delivery performance than three baselines in terms of cache hit ratio, delivery delay, network load, and energy efficiency.     

Dendrite‐Free Lithium Plating Induced by In Situ Transferring Protection Layer from Separator

Lithium (Li) metal anodes are regarded as a promising pathway to meet the rapidly growing requirements on high energy density cells, owing to their highest gravimetric capacity (3840 mAh g^?1) and their lowest redox potential. The application of Li metal anodes, however, is still hindered by undesired dendrites formation and endless consumption of liquid electrolyte due to a continuous reaction on interface of electrolyte/Li‐metal without a stable solid–electrolyte–interface (SEI) layer. A stable protection layer is formed on Li metal anode by in situ transferring the coating layer from polymer separator. The Li anode protection strategy is developed with an in situ formed protection layer transferred through the reduction of a coating layer on polymer separator. A PbZr_0.52Ti_0.48O₃ (PZT) coating layer on polypropylene (PP) separator is reduced by Li metal anode to produce a Pb metal containing composite layer, which could form Pb–Li alloy and adhere to the surface of Li metal anode after the reaction and improves the Li plating/stripping efficiency owing to the formation of a more homogenized electric field. Both the Li/Li symmetric cells and LiFePO₄/Li cells with this PZT precoated PP separators exhibit significantly improved Coulombic efficiency and cycling life.