Direct atomic scale analysis of the distribution of Cu valence states in Cu/γ-Al2O3 catalysts

In this paper, the microstructure of a 1 wt.% Cu/γ-Al₂O₃ catalyst that was reduced in a 4% hydrogen/argon atmosphere at temperatures of 523, 773 and 1073 K, is studied by Z-contrast imaging and electron energy-loss spectroscopy (EELS) in a scanning transmission electron microscope (STEM). Results show that the copper species are well dispersed when the catalyst is reduced below 523 K. At 773 K, separated Cu(I) and Cu(0) species are found existing as ring-like and bulk-like particles. This appears to indicate that the copper has not been reduced to its metallic form due to the interaction between the copper oxide and the support. Large spherical particles having core-shell structures with Cu(I) in the shells and Cu(0) in the cores are generated when the catalyst is reduced at 1073 K. The formation of partially oxidized copper species upon reduction at 1073 K is attributed to the metallic copper interaction with the alumina support. This study also demonstrates that high-spatial resolution Z-contrast imaging and EELS performed simultaneously can provide unique information on the morphology and chemistry of metal species in supported metal catalysts.     

A case study comparing defect profiles of a reused framework and of applications reusing it

The benefits of software reuse have been studied for many years. Several previous studies have observed that reused software has a lower defect density than newly built software. However, few studies have investigated empirically the reasons for this phenomenon. To date, we have only the common sense observation that as software is reused over time, the fixed defects will accumulate and will result in high-quality software. This paper reports on an industrial case study in a large Norwegian Oil and Gas company, involving a reused Java class framework and two applications that use that framework. We analyzed all trouble reports from the use of the framework and the applications according to the Orthogonal Defect Classification (ODC), followed by a qualitative Root Cause Analysis (RCA). The results reveal that the framework has a much lower defect density in total than one application and a slightly higher defect density than the other. In addition, the defect densities of the most severe defects of the reused framework are similar to those of the applications that are reusing it. The results of the ODC and RCA analyses reveal that systematic reuse (i.e. clearly defined and stable requirements, better design, hesitance to change, and solid testing) lead to lower defect densities of the functional-type defects in the reused framework than in applications that are reusing it. However, the different “nature” of the framework and the applications (e.g. interaction with other software, number and complexity of business logic, and functionality of the software) may confound the causal relationship between systematic reuse and the lower defect density of the reused software. Using the results of the study as a basis, we present an improved overall cause–effect model between systematic reuse and lower defect density that will facilitate further studies and implementations of software reuse.

延庆地区水头村泥石流形成条件及发展趋势

水头村泥石流沟是延庆地区典型沟谷型泥石流沟之一,具易发性高、危险性大的特点,严重威胁下游水头村村民。本文以水头村泥石流沟为研究对象,通过精细调查与GIS统计分析,获取了该流域降雨、地形地貌、物质来源等信息,对泥石流流域分区特征和形成条件进行研究,综合14个识别因子,确定了该泥石流沟的发展阶段,并预测其发展趋势,通过单沟泥石流堆积区公式预测了该流域最大危险区,并提出了防治措施建议。研究表明：水头村泥石流沟内松散堆积物动储量达27.96万 m³,其中以残坡积和冲洪积为主要物源;该泥石流属于暴雨-沟谷型-支沟群发型泥石流沟,发展阶段处于形成期,最大危险区面积为0.737 km²,威胁沟口水头村住户21户59人和红水公路350 m。建议采用定期巡视+局部物源稳固+清理排导槽相结合的防治措施。研究成果可为该区泥石流灾害防治提供基础数据支撑和科学依据。     

飞轮调速器反馈控制系统的混沌及控制

建立了飞轮调速器反馈控制系统的动力学方程,利用系统的相图和Poincar6映射图分析了系统的混沌形成过程．通过对飞轮调速器反馈控制系统增加一个比例微分反馈控制器,利用它控制系统从混沌运动转化为周期运动．数值仿真表明了该控制方法在飞轮调速器反馈控制系统的混沌控制中的有效性与可行性,可利用适当的控制强度镇定系统中不稳定的周期轨道．     

深潜型海水液压动力系统的研究

以海水直接作为工作介质的海水液压传动在深海应用具有系统简单、维护方便等突出优势.研制一种深潜型海水液压动力系统,该系统由深潜电机驱动,压力10～14 MPa,输出流量30 L/min,设计工作深度4 000 m,该动力系统可用于驱动海水液压水下作业工具.介绍该系统的组成、工作原理、重要参数的选择和确定以及关键元器件的研制、水下漏电保护、污染控制等关键技术问题.目前,该系统已交付现场使用,试验表明,该系统很好地满足了海水液压水下作业工具的要求.     

浅谈涂料生产企业环境限量物质的控制

简要介绍了涂料生产企业环境限量标准及指令;并分析了各项标准要求,确定环境物质风险,结合企业实际情况进行讲解分析。     

边界元区域积分奇异性的半解析处理法

本文提出一种处理二维弹塑性边界元区域奇异积分的半解析方法。首先通过三角极坐标变换降低奇异阶数,对八节点等参元,可利用其形状函数和基本解的特点消除强奇异性。最终得到的计算式简明易于程序实现,算例结果表明了该方法的有效性。     

容桂水道特大桥中主墩承台钢套箱围堰施工

容桂水道特大桥为广珠城际轨道交通控制工程,主跨为目前世界最大跨度无碴轨道铁路刚构桥,其中主墩位于深10m的水道内.经过多方案比较,主墩承台采用单壁钢套箱施工方案,介绍了钢套箱的设计原则和施工过程.通过具体工程实践,采用自制的钢套箱节约了工期及成本,取得了成功.     

对职高语文教学的几点探索

就如何在职高语文教学中用人格魅力影响学生,激发学生的动机和培养他们的实际能力方面提出了有效的教学方法.     

Hidden failure identification and protection of multi‐grounding fault in secondary circuit of potential transformer

Hidden failures as potential faults in relay protection are lethal for power systems. Multi‐grounding fault in the secondary circuit of a potential transformer (PT) is a typical hidden failure. When this hidden fault happens, zero‐sequence voltage of computer relaying will shift. Then it will result in the mis‐operation of zero‐sequence directional protection, which may cause a cascading failure. In this paper, we analyze the impact on zero‐sequence directional protection caused by multi‐grounding fault first. Then in order to solve the problem, we analyze the characteristic of the affected voltage and current. We find that the zero‐sequence voltage of the special phase is in phase with its negative sequence voltage under normal circumstance, but this is not true in this hidden failure. As a consequence, we propose an identification method of multi‐grounding fault in a PT and a new zero‐sequence direction algorithm that can avoid the mis‐operation of the zero‐sequence directional protection. Finally, the results of simulation prove the correctness of the theoretical analysis and the effectiveness of the identification method and the new zero‐sequence direction algorithm. © 2016 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.