基于CDMA导频信号的动目标探测方法

论述了一种利用CDMA下行导频信号进行动目标探测的方法。根据CDMA导频信号良好的无源探测性能,通过在时频域内对实时数据进行长时间相干已积累来提取目标信息,给出了一个基于单接收机的实验系统,并通过该系统完成了动目标的多普勒频率和距离检测。实验结果证明了CDMA信号用作无源探测是可行的。     

IMS计费部署及关键问题研究

随着IMS网络及业务的快速发展,IMS计费也日益受到关注.本文基于IMS网元计费能力提出IMS计费部署架构,还介绍了IMS业务离线及在线计费的基本流程,最后对计费存在的一些关键问题进行分析.     

Influence of hydrogenation on the dark current mechanism of HgCdTe photovoltaic detectors

The influence of hydrogenation on the dark current mechanism of HgCdTe photovoltaic detectors is studied.The hydrogenation is achieved by exposing samples to a H_2/Ar plasma atmosphere that was produced during a reactive ion etching process. A set of variable-area photomask was specially designed to evaluate the hydrogenation effect.It was found that the current-voltage characteristics were gradually improved when detectors were hydrogenated by different areas. The fitting results of experimental results at reverse bias conditions sustained that the improvement of current-voltage curves was due to the suppression of trap assisted tunneling current and the enhancement of minority lifetime in the depletion region. It was also found that the dominative forward current was gradually converted from a generation-recombination current to a diffusion current with the enlargement of the hydrogenation area, which was infered from the ideality factors by abstraction of forward resistance-voltage curves of different detectors.     

A novel TFS-IGBT with a super junction floating layer

A novel trench field stop (TFS) IGBT with a super junction (SJ) floating layer (SJ TFS-IGBT) is proposed.This IGBT presents a high blocking voltage (>1200 V), low on-state voltage drop and fast turn-off capability. A SJ floating layer with a high doping concentration introduces a new electric field peak at the anode side and optimizes carrier distribution, which will improve the breakdown voltage in the off-state and decrease the energy loss in the on-state/switching state for the SJ TFS-IGBT. A low on-state voltage (VF) and a high breakdown voltage (BV) can be achieved by increasing the thickness of the SJ floating layer under the condition of exact charge balance. A low turn-off loss can be achieved by decreasing the concentration of the P-anode. Simulation results show that the BV is enhanced by 100 V, VF is decreased by 0.33 V (at 100 A/cm2) and the turn-off time is shortened by 60%, compared with conventional TFS-IGBTs.     

移动P2P视频流媒体体系下的帧位分配算法

针对移动P2P流媒体系统中存在多视频源的特点,提出了多视频源串行和并行调度算法。串行调度算法,接收Peer通过实时侦测的QoS变化触发视频源的更换,并通过流序列时间模型来同步各个视频源。并行调度算法,多个视频源同时提供服务,并通过帧位分配算法分配各视频源的传输任务。帧位分配算法首先将视频序列分成包含固定帧数的块系列,然后进行块级位分配以充分考虑帧间效应。对于单个帧块位分配问题,算法将其建模成了非线性规划问题,通过引入分段线性R-D模型将该问题进一步转换成了普通的线性规划问题,并提出了一个贪婪实现策略。实验结果显示流分配算法能获得高效、平稳的视频质量,而且时间效率也非常高,能较好的满足移动P2P视频流媒体系统的实时性。     

碳纤维表面金属化及其场发射特性研究

采用化学镀镍对碳纤维(Carbon fibers,CNFs)表面金属化,研究不同厚度的表面金属化碳纤维的场发射性能。实验结果表明,碳纤维表面金属化后体电阻率明显降低,场发射性能显著提高;厚度不同的金属化碳纤维的场发射性能不同。当化学镀时间为30 min,镍金属膜厚约3.25μm时,碳纤维体电阻率ρ降至1.35×10-4Ω.cm,场发射性能最优,当电压为638 V时出现亮点,电压为1 425 V时,亮度最高达988 cd/m2。