基于H.26L的视频抗误码方法研究

根据视频编码标准H．26L算法的新特点，基于用户自定义信息域，提出多种视频抗误码方法．在编码端根据视频信息的重要程度相应采用了自适应不等保护算法，当恢复视频仍有误码时，则在解码端使用时／空误码掩盖方法提高恢复视频质量．通过编解码端的信息交互，使用SP帧来防止误码扩散．在高误码率环境下，与只使用筒单误码掩盖和BCH(5ll，493)码保护相比，综合使用文中给出的视频抗误码方法。恢复图像的峰值信噪比可以提高7-18dB．该算法与H．26L标准兼容，具有实用价值．     

杂质对化成过程影响的初步研究

讨论聚合物锂离子电池在化成时出现充电异常的主要影响因素。通过实验表明:在生产中残留在电池中的DBP、CH3OH、H2O是造成电池化成过程充电异常的主要杂质并可能影响SEI层的性质。     

Some methodological deficiencies in studies on traffic accident predictors

The paper discusses some methodological problems in (psychological) research on traffic accident predictors and reviews a convenience sample of the literature. Three methodological aspects are identified as being important: reliability of accident predictors, time period for accidents used as dependent variable, and culpability for accidents. Papers are scrutinized and most are found to be wanting in these aspects. Traffic researchers do not adhere to, or hardly even discuss, these basic methodological problems. It is concluded that the current research into (psychological) accident predictors is fraught with methodological deficiencies. Why most studies seem to be deficient in these aspects is not clear, as several researchers have pointed out these problems.     

电解液纯化对锂离子电池负极电化学性能影响

运用电化学阻抗谱(EIS)、恒流充放电和循环伏安测试,研究了1 mol/L LiPF_6/(EC+DEC+DMC)(体积比1∶1∶1)电解液中4A分子筛除水处理对石墨电极电化学性能的影响。研究表明:石墨电极在经4A分子筛处理后的电解液中能形成性能优异的固体电解质相界面(SEI)膜,降低了SEI膜的阻抗,改善了石墨电极的循环性能,得到了更优异的电化学性能。     

Storage behavior of LiNi1/3Co1/3Mn1/3O2/artificial graphite Li-ion cells

A series of Li-ion cells containing LiNi_1/3Co_1/3Mn_1/3O₂ and artificial graphite as the active materials, have been stored at various temperatures from 0 to 70 °C. The 3-electrode impedance study shows that both the solid electrolyte interphase (SEI) film resistance and charge-transfer resistance of the negative electrode first decrease and then increase during storage at 70 °C, while both resistances for the positive electrode increase under this condition. The reversible capacity loss of the 3-electrode cell, which is possibly attributed to dissolution of SEI film, accounts for over half of the total capacity loss after 5 weeks of storage. Gases generated from the swelling aged cell at 60 °C are mainly attributed to the reduction of the electrolyte on the negative electrode. A further study on the side-reaction has been done on graphite electrodes and separators, indicating that SEI films may be rearranged and reformed on negative electrodes, and that some pores on the positive electrode side of separator are blocked due to the oxidation of electrolyte, resulting in poor Li-ion transfer and rise of the ohmic resistance during storage at elevated temperature. However, at 0 °C, this side-reaction is impeded.     

解决聚合物锂离子电池气胀现象的新方法

采用气相色谱与质谱联机的方法,对聚合物锂离子电池气胀现象的机理进行了研究,引入电解液添加剂VC(1,2-二亚乙烯基碳酸酯)进行自由基链式聚合反应,生成聚烷基碳酸锂化合物。从而有效地捕捉了由于电解液分解产生的烷基自由基,消除了气体产生的可能性,并且对正负极材料没有副作用。电池气胀现象得到了根本的改善,证明了气胀的自由基机理。     

Effect of electrolyte composition on initial cycling and impedance characteristics of lithium-ion cells

Hybrid-electric vehicles require lithium-battery electrolytes that form stable, low impedance passivation layers to protect the electrodes, while allowing rapid lithium-ion transport under high current charge/discharge pulses. In this article, we describe data acquired on cells containing LiNi_0.8Co_0.15Al_0.05O₂-based positive electrodes, graphite-based negative electrodes, and electrolytes with lithium hexafluorophosphate (LiPF₆), lithium tetrafluoroborate (LiBF₄), lithium bis(oxalato)borate (LiBOB) and lithium difluoro(oxalato) borate (LiF₂OB) salts. The impedance data were collected in cells containing a Li–Sn reference electrode to determine effect of electrolyte composition and testing temperature on individual electrode impedance. The full cell impedance data showed the following trend: LiBOB > LiBF₄ > LiF₂OB > LiPF₆. The negative electrode impedance showed a trend similar to that of the full cell; this electrode was the main contributor to impedance in the LiBOB and LiBF₄ cells. The positive electrode impedance values for the LiBF₄, LiF₂OB, and LiPF₆ cells were comparable; the values were somewhat higher for the LiBOB cell. Cycling and impedance data were also obtained for cells containing additions of LiBF₄, LiBOB, LiF₂OB, and vinylene carbonate (VC) to the EC:EMC (3:7 by wt.) + 1.2 M LiPF₆ electrolyte. Our data indicate that the composition and morphology of the graphite SEI formed during the first lithiation cycle is an important determinant of the negative electrode impedance, and hence full cell impedance.     

影响锂离子蓄电池负极SEI膜结构及性质的因素

结合近几年关于SEI膜的研究结果,综述了影响锂离子蓄电池负极SEI膜结构及性能的各种因素,其中包括负极材料种类、导电剂的分布、电解液溶剂、电解质盐、电解液添加剂、杂质、化成条件、环境温度等因素。     

原位构建富氟SEI的凝胶电解质用于金属锂二次电池

以六氟磷酸锂（LiPF₆）为四氢呋喃的聚合引发剂制备凝胶电解质,同时作为氟源在金属锂负极表面原位构建富含LiF的固态电解质界面层（solid electrolyte interface,SEI）来抑制锂枝晶的生长以及金属锂/电解液之间的副反应。所制备的凝胶电解质具有较高的室温离子电导率（1.33 mS·cm^-1）和较宽的电化学稳定窗口（4.5 V）。原位聚合方式组装金属锂对称电池循环后,锂负极表面没有明显的锂枝晶和被损毁的形貌出现;XPS结果表明锂负极表面生成了富含LiF的SEI。组装的LiFePO₄全电池在1 C的电流密度下,稳定循环400周后仍保持118.7 mAh·g^-1的放电比容量。得益于四氢呋喃在开环聚合反应过程中,促进了LiPF₆分解反应平衡的正向移动,在锂负极表面形成稳定的富含LiF的SEI,能够抑制锂枝晶的生长并防止其被持续性的腐蚀破坏。     

基于持续学习和联合特征提取的特定辐射源识别

针对特定辐射源识别(SEI)识别准确率较低和单次样本学习花销较大的问题,该文提出一种基于增量式学习的SEI方法,设计多个连续增量深度极限学习机(CIDELM)。从截获信号中分别提取变分模态分解(VMD)后的Hilbert谱投影和高阶谱,降维后作为射频指纹(RFF)用于分类;在极限学习机(ELM)中采用稀疏自编码结构对多个隐含层进行无监督训练,并利用参数搜索策略确定最佳隐含层数和隐节点个数,实现对多批次标记样本的连续在线匹配。实验结果表明,该方法对不同调制方式、载波频率和收发距离均能表现出良好兼容性,能够实现对于多个辐射源个体的有效识别。