Highly active sites of low spin FeⅡN4species:The identification and the ORR performance

Over recent years,catalytic materials of Fe-N-C species have been recognized being active for oxygen reduction reaction(ORR).However,the identification of active site remains challenging as it generally involves a pyrolysis process and mixed components being obtained.Herein Fe₃C/C and Fe₂N/C samples were synthesized by temperature programmed reduction of Fe precursors in 15%CH₄/H₂and pure NH₃,respectively.By acid leaching of Fe₂N/C sample,only single sites of FeN₄species were presented,providing an ideal model for identification of catalytic functions of the single sites of FeN₄in ORR.A correlation was conducted between the concentration of Fe^ⅡN₄in low spin state by Mossbauer spectra and the kinetic current density at 0.8 V in alkaline media,and such a structure-performance correlation assures the catalytic roles of low spin Fe^ⅡN₄ species as highly active sites for the ORR.     

基于负荷综合权值的配电网孤岛划分策略

提出一种基于负荷综合权值的孤岛划分策略。采用熵值法和最优-最劣法（best-worst method,BWM）对负荷进行评价以得到负荷的客、主观权值,并通过相对熵耦合负荷客、主观权值以进一步求出负荷综合权值;对各负荷相对于不同DG的重要程度进行排序,并依据此排序将负荷纳入DG形成的孤岛中。通过IEEE-69节点配电网系统进行验证,结果表明：所提孤岛划分策略能够有效地保证配电网中重要负荷的供电可靠性并减少了线路损耗。     

Effect of the Three Gorges Reservoir on vertical distribution of suspended sediment concentration and estimation accuracy of depth-average concentration in downstream reaches

The sediment regime in the middle Yangtze River has been significantly changed from quasi-equilibrium to nonequilibrium since the impoundment of the Three Georges Reservoir (TGR). To understand the effects of the TGR on vertical distribution of suspended sediment concentration (SSC) and estimation accuracy of mean concentration, vertical sediment concentration and flow velocity data at the Shashi and Jianli hydrological stations in the reach before and after the impoundment were collected. Comparisons and analysis of vertical profiles of SSC before and after the TGR impoundment show that after the impoundment of the TGR, due to the coarsening of sediment particle size, the reduction in sediment load, and the significant decrease in sediment saturation, the vertical distribution of SSC in the downstream reaches became more uneven under medium and low water flows, which was reflected in the vertical gradient and the fluctuation degree of SSC significantly increased. In addition, the depth-average sediment concentrations were calculated by the selected-point method and the mean values calculated by the “multi-point method” were regarded as the “true mean” to evaluate the accuracy of the mean value calculated by the “few-point method.” It was found that the relative errors for the selected-point method were mainly positive before impoundment but mainly negative after impoundment. Additionally, the correction factors of one-point, two-point, and three-point methods and the position of the near-bed substituted point for the five-point method were given to reduce the error when the point measurements were used to calculate the depth-average sediment concentration in the downstream reaches.     

支持O2O的时空众包激励技术研究

在这个流行元素日新月异的时代,消费者的口味越来越难以把控,商家的判别标准将极大决定店铺的业绩水平.文章介绍了时空众包的概念,研究在商城背景下,利用时空众包思想设计一种能持续有效执行的机制来提高O2O模式的资源利用率问题.     

一种基于深度学习的视网膜病变图像识别方法

为解决医学上糖尿病性视网膜病变图像人工识别困难、精度差等问题,提出一种基于多特征融合的卷积神经网络识别方法。在VGG-16模型的基础上,通过融合每层网络上的局部特征,增强模型的特征提取能力。选用Softmax分类器,使病变图像识别更加准确。使用OpenCV图像处理工具采用加噪、上下左右不同角度翻转、调节对比度等5种方式扩充训练集。实验结果表明,基于多特征融合的深度学习框架图像识别系统在数据集上的平均识别精度达到94.23%,相较于Alex-Net、Google-Net、Compact-Net、ResNet-101等模型分别提高了10.56%、7.80%、6.01%、0.02%,验证了该方法的有效性。该模型具有很好的鲁棒性。     

横向整合战略下异质车辆库存路径优化模型

以实现供货商联盟期望物流成本最小化为目标,针对需求随机波动下的多供货商多产品库存路径问题（IRP）进行了研究。基于横向整合战略,设计了供货商联盟成员间车辆配送成本的合理分摊方式。考虑零售商配送软硬时间窗和库存服务水平要求,构建了多供货商多产品的异质车辆库存路径混合整数随机规划模型,并利用需求累积分布逆函数将其转化为确定型规划模型。然后设计改进遗传算法求解该确定型规划模型。算例分析结果显示,使用异质车辆配送可以比使用同质重型和轻型车辆分别降低供货商联盟总成本8.3%和11.92%,分别提升配送车辆装载率24%和17%。敏感性分析结果表明,无论供货商供货数量占联盟总供货数量比例和零售商商品需求变异系数如何变化,采用异质车辆配送的供货商联盟总成本都能得到有效降低;且需求变异系数越大,采用异质车辆配送的优势越明显。     

基于无线传感网络的爆炸场振动监测系统

爆炸场振动测试中节点分布范围广、数量多,对各测试节点的状态监控及全局管理难以有效实现,传统测试方案中节点部署后难以快速更改状态;针对上述问题,依据模块化、标准化和稳定性原则,设计了一种基于无线技术的振动监测系统;给出了爆炸场振动监测系统的基本功能单元,包括数据采集设备、无线组网设备;数据采集设备具有高精度采集、数据存储、高精度同步、定位定姿等功能;利用无线网桥技术构建了覆盖广域范围的无线网络,支持IEEE802.11 n/ac协议,实现了对远程分布式测试节点的集中管理、状态监控、数据传输,也可对指定测试节点的工作模式进行快速设置,以满足测试需求;测试节点的振动测量范围为0～10 g,室外1公里数据传输;通过模拟测试试验验证了系统的有效性,各项功能满足工程需要.     

Spark中一种高效RDD自主缓存替换策略研究

由于并行计算框架Spark缓存替换算法的粗糙性,LRU（least recently used）算法并未考虑RDD的重复使用导致易把高重用数据块替换出内存且作业执行效率较低等问题。通过优化权重模型和改进替换策略,提出了一种高效RDD自主缓存替换策略（efficient RDD automatic cache,ERAC）,包括高重用自主缓存算法和缓存替换分级算法,可实现高效RDD的自主缓存和缓存目标的分级替换。最后利用SNAP（Stanford network analysis project）提供的标准数据集将ERAC和LRU、RA（register allocation）等算法进行了对比实验,结果显示ERAC算法能够有效提高Spark的内存利用率和任务执行效率。     

相关向量机预测电池健康状态和剩余有效寿命

相关向量机(relevance vector machine,RVM)算法由于其高稀疏性的特征,比有同样原始模型的支持向量机(support vector machine,SVM)算法有着更多的优势,在锂离子电池剩余有效寿命的研究中受到了关注.总结了现有的基于RVM算法的预测模型,介绍针对于电池寿命中RVM算法的改进,为之后的研究提供一定的参考.     

基于支持向量机的炒作微博识别方法

微博是舆论传播的中心和渠道,同时参与舆论的形成、发展与引导过程,其自媒体发布、意见领袖参与等因素在一定程度上造成了微博谣言、虚假炒作、社会动员等现象。针对炒作微博的传播特点,分析其群体的隐蔽策划现象,挖掘出普通微博和炒作微博在传播网络结构、转发增量统计等方面的差异。通过社交网站的应用程序接口对目标微博的所有评论、转发和点赞用户进行信息获取,构建该微博的传播网络,利用社团模块度、平均最短路径和网络直径这3个属性度量该网络的紧密程度,基于支持向量机对所抽取的微博进行分类,进而识别出炒作微博。实验结果表明,该方法对微博传播用户的属性信息依赖小以及传播网络结构特征敏感,并且具有较高的炒作微博识别准确率。