10G EPON系统关键技术的分析

随着智能电网、三网融合、网络视频等高带宽业务需求的不断增长,1 G EPON网络向10 G EPON升级已是大势所趋.文章首先介绍了10 G EPON系统标准的最新进展,然后对10 G EPON系统波长分配、FEC、光功率预算、MPCP等关键技术进行分析,最后结合智能电网信息通信业务对EPON网络的需求,论述1 G EPON向10 G EPON平滑演进的方式.     

不对称单相感应电机对称补偿的参数辨识方法

为了实现不对称单相感应电机的矢量控制,给出了一种新的不对称单相感应电机参数辨识方法。依据不对称单相感应电机的数学模型分析,通过参数折算和对称补偿实现对称控制,消除了空载实验所测电机参数受不对称磁场影响而产生的误差。辨识数据采用了母线电压重构和离散快速傅里叶变换(DFFT)技术,并进行了死区补偿,提高了辨识精度。通过基于SVPWM的仿真实验和系统电路实验,证实了方法的正确性和精确性,实现了电机参数的离线辨识。     

基于非对称阿基米德Copula的多变量水文干旱联合概率研究

推导了5种常用3维非对称阿基米德Copulas函数的条件Copulas和密度函数,阐述了这类Copulas函数研究水文干旱特性联合分布的应用技术问题。以渭河流域北洛河状头站的径流序列为例,干旱变量的边际分布参数分别采用矩法、概率权重法、极大似然法和遗传算法进行计算和选优,并进行了分布函数拟合度检验。变量相依性的度量表明干旱变量间有较强的相依性;根据AIC,BIC和RMSE准则,M12 Copula拟合效果最优。最后,进行了M12 Copula的拟合度检验,计算了北洛河状头站3维水文干旱变量组合的联合概率、条件概率和相应的重现期。     

中国水资源空间不均匀性定量评价

降水及水资源量的空间不均匀性是其基本特性之一。本文基于中国第二次水资源综合评价结果,利用洛伦兹曲线计算得到反映水资源不均匀性强弱的基尼系数及反映不均匀性来源的洛伦兹不对称系数。结果表明：中国不同类型水资源均表现出比较不均匀或非常不均匀的空间分布特征;各一级分区水资源空间不均匀性与分区面积、平均降水量及自然条件等因素有关,从东部、南部沿海向内陆地区逐渐增加;同一分区内总体上表现为降水空间基尼系数最小,地下水资源、水资源总量、地表水资源空间基尼系数依次增大,但南部分区地表水和水资源总量空间基尼系数接近;水资源的不均匀性呈现出水资源量较少区域主导的非对称性或较为对称分布的特征。     

基于XML的安全数据交换模型

基于XML技术设计了一种安全高效的数据交换模型,实现了数据和密钥的安全传输和存储.该模型结合XKMS简化了公钥注册与管理,能够为跨系统的多方数据交换提供统一、安全的服务.介绍了模型建立的具体方案,包括XML文档的加解密、数据加密密钥DEK的生成、数据加密密钥存储管理,讨论了该模型使用XKMS管理公钥的方法和提供的安全机制.     

Formation of a Surficial Bifunctional Nanolayer on Nb2O5 for Ultrastable Electrodes for Lithium‐Ion Battery

Safe and long cycle life electrode materials for lithium‐ion batteries are significantly important to meet the increasing demands of rechargeable batteries. Niobium pentoxide (Nb₂O₅) is one of the highly promising candidates for stable electrodes due to its safety and minimal volume expansion. Nevertheless, pulverization and low conductivity of Nb₂O₅ have remained as inherent challenges for its practical use as viable electrodes. A highly facile method is proposed to improve the overall cycle retention of Nb₂O₅ microparticles by ammonia (NH₃) gas‐driven nitridation. After nitridation, an ultrathin surficial layer (2 nm) is formed on the Nb₂O₅, acting as a bifunctional nanolayer that allows facile lithium (Li)‐ion transport (10–100 times higher Li diffusivity compared with pristine Nb₂O₅ microparticles) and further prevents the pulverization of Nb₂O₅. With the subsequent decoration of silver (Ag) nanoparticles (NPs), the low electric conductivity of nitridated Nb₂O₅ is also significantly improved. Cycle retention is greatly improved for nitridated Nb₂O₅ (96.7%) compared with Nb₂O₅ (64.7%) for 500 cycles. Ag‐decorated, nitridated Nb₂O₅ microparticles and nitridated Nb₂O₅ microparticles exhibit ultrastable cycling for 3000 cycles at high current density (3000 mA g^?1), which highlights the importance of the surficial nanolayer in improving overall electrochemical performances, in addition to conductive NPs.     

Sensitive and Reversible Detection of Methanol and Water Vapor by In Situ Electrochemically Grown CuBTC MOFs on Interdigitated Electrodes

The in situ electrochemical growth of Cu benzene‐1,3,5‐tricarboxylate (CuBTC) metal–organic frameworks, as an affinity layer, directly on custom‐fabricated Cu interdigitated electrodes (IDEs) is described, acting as a transducer. Crystalline 5–7 µm thick CuBTC layers are grown on IDEs consisting of 100 electrodes with a width and a gap of both 50 µm and a height of 6–8 µm. These capacitive sensors are exposed to methanol and water vapor at 30 °C. The affinities show to be completely reversible with higher affinity toward water compared to methanol. For exposure to 1000 ppm methanol, a fast response is observed with a capacitance change of 5.57 pF at equilibrium. The capacitance increases in time followed diffusion‐controlled kinetics (k = 2.9 mmol s^?0.5 g^?1_CuBTC). The observed capacitance change with methanol concentration follows a Langmuir adsorption isotherm, with a value for the equilibrium affinity K _e = 174.8 bar^?1. A volume fraction f _MeOH = 0.038 is occupied upon exposure to 1000 ppm of methanol. The thin CuBTC affinity layer on the Cu‐IDEs shows fast, reversible, and sensitive responses to methanol and water vapor, enabling quantitative detection in the range of 100–8000 ppm.     

Monolithic and Flexible ZnS/SnO2 Ultraviolet Photodetectors with Lateral Graphene Electrodes

A continuing trend of miniaturized and flexible electronics/optoelectronic calls for novel device architectures made by compatible fabrication techniques. However, traditional layer‐to‐layer structures cannot satisfy such a need. Herein, a novel monolithic optoelectronic device fabricated by a mask‐free laser direct writing method is demonstrated in which in situ laser induced graphene‐like materials are employed as lateral electrodes for flexible ZnS/SnO₂ ultraviolet photodetectors. Specifically, a ZnS/SnO₂ thin film comprised of heterogeneous ZnS/SnO₂ nanoparticles is first coated on polyimide (PI) sheets by a solution process. Then, CO₂ laser irradiation ablates designed areas of the ZnS/SnO₂ thin film and converts the underneath PI into highly conductive graphene as the lateral electrodes for the monolithic photodetectors. This in situ growth method provides good interfaces between the graphene electrodes and the semiconducting ZnS/SnO₂ resulting in high optoelectronic performance. The lateral electrode structure reduces total thickness of the devices, thus minimizing the strain and improving flexibility of the photodetectors. The demonstrated lithography‐free monolithic fabrication is a simple and cost‐effective method, showing a great potential for developement into roll‐to‐roll manufacturing of flexible electronics.