Corrosion mechanism and corrosion model of Mg-Y alloy in NaCl solution

Corrosion of Mg–Y alloy was studied using electrochemical evaluations, immersion tests and SEM observations. Corrosion mechanisms of Mg-(0.25 and 2.5) Y alloy and Mg-(5, 8, and 15) Y alloy were uniform corrosion and pitting corrosion respectively, and the content of Mg_(24)Y_5 phases determined its effect acting as cathode to accelerate the corrosion or corrosion barrier to inhibit the corrosion. Corrosion resistance of Mg-(0.25, 2.5, 5, 8, and 15) Y alloys was as follows: Rt(Mg-0.25Y) Rt(Mg-8Y) Rt(Mg-15Y) Rt(Mg-5Y) Rt(Mg-2.5Y). Y could significantly improve the corrosion resistance of the Mg-Y alloy, but the excess of Y deteriorated the corrosion resistance of the Mg-Y alloy. The optimum content of Y in the studied alloys was 2.5%.     

基于典型故障类型的分布式光伏并网对电压稳定性的影响

为了准确分析分布式光伏并网对电压稳定的影响,针对光伏阵列,给出了一种基于实时数字仿真仪(RealTime Digital Simulator,RTDS)软件平台的光伏并网建模方法.介绍了光伏发电的原理,对分布式光伏并网系统接入电网的方法进行了详细分析和研究.然后,基于光照强度和环境温度在RTDS软件平台上搭建了一个光伏发电并网模型,对光伏并网系统进行了仿真研究.仿真结果表明,不同的系统故障状态下,光伏并网对公网侧和并网侧电压稳定性的影响不同.     

论苏童小说《米》的意象叙事

意象是苏童小说叙事的特色之一。苏童创造性地把意象的审美机制引入叙事文学领域,以意象叙事代替传统的情节叙事,改变了传统小说较为单调的叙事方式,使文本具备了现代小说独有的弹性与张力。意象叙事的创作策略在苏童小说《米》中运用得最为突出,作家营构了大量繁复隽永、独具特色的意象来推动故事情节的发展,意象成为叙事活动的一部分,为作品增添了更加复杂的内涵和更为深厚的意蕴。     

新型支臂千斤顶在解决水轮发电机组振动的应用

根据对芭蕉河水电公司蕉4号水轮发电机组振动值偏大的案例,系统分析和探讨了造成水轮发电机组振动的原因及解决方案。针对支臂千斤顶的结构、安装等,采用精心制作与改造的支臂千斤顶解决水轮发电机组振动问题。经4个月的持续监测跟踪分析,该机组径向振动值超标彻底消除,达到了正常稳定运行要求。     

水布垭大坝面板修补前后总渗流量综合分析

水布垭水电站大坝为目前世界上已建成的最高混凝土面板堆石坝,其总渗漏量为大坝安全稳定运行的重要评价指标。根据水布垭大坝面板历次修补情况,从实测数据出发对比分析面板修补前后渗流量变化,采用统计模型分析了库水位、降雨量、温度、面板破损及修补等因素对总渗流量的影响规律,与同类工程对比,说明大坝面板的缺陷修补效果较好。     

寒区流冰撞击输水隧洞的数值模拟分析

位于西北寒区的长距离输水工程在流冰期输水过程中,不同流速和不同碰撞角度的流冰对输水隧洞衬砌会形成不同程度的撞击作用,导致输水隧洞衬砌产生破损,因此为了研究该地区流冰对输水隧洞的撞击作用,采用了理论分析结合数值模拟的方法。研究结果表明:当流冰速度一定时,随着流冰与隧洞衬砌碰撞角度的增大,其对隧洞衬砌的影响呈现出近似的非线性(多项式)关系;当碰撞角度一定时,随着流冰速度的增大,其对隧洞衬砌的影响呈现出近似的线性关系;综合不同组合工况还可以发现流冰速度对隧洞衬砌的影响作用要强于碰撞角度对其的影响作用,且碰撞角度对隧洞衬砌所受的撞击力及隧洞碰撞区位移的影响较为不明显。     

Winglet geometry effects on tip leakage loss over the plane tip in a turbine cascade

The effects of winglet offset distance, winglet coverage, and winglet cross section on the over-tip leakage loss for the plane tip have been investigated experimentally in a turbine blade cascade for a tip gap height-to-span ratio of h/s = 1.36 %. The results show that the over-tip leakage loss for the full coverage winglet increases steeply with increasing the winglet offset distance. This loss generation is attributed to flow disturbances over the forward-facing and backward-facing steps within the tip gap. The winglet flush mounted to the tip surface provides the best result. With the leading edge winglet portion or without it, the both-side winglet always provides better aerodynamic performance than the corresponding pressure-side winglet or suction-side winglet. Longer coverage of the both-side winglet leads to lower loss. Therefore, the full coverage winglet performs best in the loss reduction for the plane tip. In general, thinner winglet leads to better aerodynamic result, and the winglet cross section having a slant bottom surface with the smallest thickness at its outer end is recommended.     

微信中的政治学资源及其利用

微信是一种新兴的移动新媒体平台,具有强大的移动学习功能,蕴含着海量的政治学信息资源.通过打造政治学微信互动课堂,精心构建政治学微信公众账号等资源,形成和强化运用微信平台开展政治学教育的各种运行机制,可以充分发挥微信功能及其政治学资源在政治学教育中的独特优势,消除其弊端,开创移动新媒体时代的政治学教育新途径.     

页岩气基质纳米通道流动模拟研究

结合活性炭表面扩散系数计算原理,建立页岩气在纳米孔道中的流动方程。模拟结果表明:通道半径为0~8nm,通道中以吸附气的表面扩散为主,压力的影响可忽略不计;通道半径大于10 nm时,表面扩散通量相对较少,压力的影响不可忽略;当通道半径高于50 nm时,自由分子流动通量可以达到99%,压力是气体分子传输速度的主要影响因素。     

Composition dependence of phase structure and electrical properties of (1−y)Bi1−xNdxFeO3−yBiScO3 ceramics

In this work, we have studied a new lead-free ceramic of(1-y)Bi_(1-x)Nd_xFeO_(3-y)BiScO_3(0.05≤x≤0.15 and 0.05≤y≤0.15) prepared by a conventional solid-state method, and the influences of Nd and Sc content on their phase structure and electrical properties were investigated in detail. The ceramics with 0.05≤x≤0.10 and 0.05≤y≤0.15 belong to an R3 c phase, and the rhombohedral-like and orthorhombic multiphase coexistence is established in the composition range of 0.125≤x≤0.15 and y=0. The electrical properties of the ceramics can be enhanced by modifying x and y values. The highest piezoelectric coefficient(d33~51 p C/N) is obtained in the ceramics with x=0.075 and y=0.125, which is superior to that of a pure BiFeO_3 ceramic. In addition, a lowest dielectric loss(tan δ~0.095%, f=100 k Hz) is shown in the ceramics with x=0.15 and y=0 due to the involvement of low defect concentrations, and the improved thermal stability of piezoelectricity at 20–600oC is possessed in the ceramics. We believe that the ceramics can play a meaningful role in the high-temperature lead-free piezoelectric applications.