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.     

VaspCZ:一个提高效率的VASP计算辅助程序

VASP(Vienna Ab-initio Simulation Package)是基于密度泛函理论的通用材料计算模拟软件。随着高性能计算平台的广泛使用和高通量计算的兴起,VASP计算任务的复杂性和数据量也大幅度提升。为了提高材料理论计算的方便程度,减少大量重复的指令和结果检查的复杂性,本文提供了一个基于Python语言的VASP计算辅助程序VaspCZ,能够大幅提高研究者的科研效率。该程序包含软件部分和API部分,软件部分提供了命令行用户界面,基于基本的Linux命令即可一键完成VASP计算的相关操作,为无编程语言基础的研究人员提供了便利。应用程序接口部分服务于具有Python语言基础的研究者,提供了底层库,使得自定义计算(如高通量计算、编写高级应用等)更为简单快捷。本程序包可以显著提高VASP的计算效率,并已经通过Github开源项目公开,提供了详细的使用文档、使用示例和API接口,有望能为广大材料理论研究者提供便利。     

Complexity of synthesis of composite service with correctness guarantee

How to compose existing web services automatically and to guarantee the correctness of the design (e.g. temporal constraints specified by temporal logic LTL, CTL or CTL*) is an important and challenging problem in web services. Most existing approaches use the process in conventional software development of design, verification, analysis and correction to guarantee the correctness of composite services, which makes the composition process both complex and time-consuming. In this paper, we focus on the synthesis problem of composite service; that is, for a given set of services and correctness constraint specified by CTL or CTL* formula, a composite service is automatically constructed which guarantees that the correctness is ensured. We prove that the synthesis problem for CTL and CTL* are complete for EXPTIME and 2EXPTIME, respectively. Moreover, for the case of synthesis failure, we discuss the problem of how to disable outputs of environment (i.e. users or services) reasonably to make synthesis successful, which are also proved complete for EXPTIME and 2EXPTIME for CTL and CTL*, respectively.     

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。     

基于轮廓波变换的织物疵点图像消噪新方法

为了实现织物疵点图像的有效消噪,使其更有利于特征提取和疵点检测,提出了基于轮廓波变换的织物疵点图像消噪新方法。综合考虑轮廓波方向子带能量的大小与织物疵点图像轮廓细节之间的关系,对Donoho多尺度分解阈值进行修正,改进了Donoho多尺度分解阈值对图像细节"过扼杀"的缺点。实验结果表明,对织物疵点图像进行基于轮廓波变换改进阈值消噪时,该方法更好地保留了织物疵点图像的轮廓细节,峰值信噪比显著提高。采用改进的轮廓波Donoho多尺度分解阈值消噪后的图像,可以更好地应用于织物疵点图像的特征提取和疵点识别。     

一种基于单条程序执行路径的错误定位方法

当程序在测试中发生错误时,将形成一条错误的程序执行路径,程序员将会花费很多精力去检测程序代码和定位最终的程序错误．提出一种基于单条程序执行路径的错误定位方法,该方法通过对程序进行反向执行,计算出多个最弱前置条件及其相对应的疑似错误语句集,并生成错误定位树,来辅助程序员进行快速错误定位．对西门子测试数据集进行的实验表明了该方法具有良好的效果．     

结合锥模型算法的修正多步拟牛顿法

提出一种解决维数较大的无约束优化问题的混合算法.该算法采用了一个开关用于切换修正多步拟牛顿算法和锥模型算法.结果表明,该算法既保留了拟牛顿算法的快速有效性,又将适用范围扩大到了二次模型逼近效果较差的函数,且对于大多数维数较大的函数都是切实可行的.     

大学生的膳食营养与营养教育

随着人们健康意识的提高,当代大学生的膳食营养与营养教育也日益受到关注。本文阐述了大学生的营养需求和合理营养对于促进大学生的健康与学习的作用,分析了大学生的营养状况及存在的问题,提出了大学生营养教育的措施。     

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.