Effect of UWS injection at low exhaust gas temperature on NO<Subscript>x</Subscript> removal efficiency of diesel engine

Urea-SCR systems have been widely used in diesel vehicles according to the strengthened NO_x (Nitrogen Oxides) emission standard. The NO_x removal efficiencies of the latest well optimized urea-SCR system are above 90 % at moderate exhaust gas temperature of 250 ~ 450 °C. However, a large amount of NO_x is emitted from diesel vehicles at cold start or urban driving conditions, when the exhaust gas temperature is not high enough for SCR catalyst activation. Although many researchs have been stuied to improve NO_x conversion efficiency at these low temperature conditions, it is still one of important technical issues. In this study, the effect of UWS injection at low exhaust gas temperature conditions is studied. This study uses a 3.4 L diesel engine equipped with a commertial urea SCR system. As a result, it is found that about 5 % of NO_x removal efficiency is improved in the NRTC test when UWS injection starts at the SCR inlet temperature of 150 °C compared to 200 °C. It is also found that urea deposits can be formed on the wall of exhaust pipe, when the local wall temperature is lower than temperature of urea decomposition.     

开关电源环路补偿计算及辅助软件Mathcad的应用

开关电源的环路补偿对电源系统的稳定性、可靠性起着决定作用,因此如何设计出合理可靠的补偿参数十分重要。介绍开关电源环路补偿的条件,并以BUCK电路为例进行环路补偿电路选择及补偿电路元件参数的计算。     

城市轨道交通列车基础制动装置温度测试方案

分析了城市轨道交通列车基础制动装置在线温度测试的重要性,介绍了温度测试技术,提出了基于热电偶、红外测温仪和热成像仪的多平台温度测试方案,以解决单一温度测试方法存在的不足。热电偶、红外测温仪和成像仪组成的多平台协同温度测试方案是获取踏面制动过程中车轮-闸瓦摩擦副温度场较理想可行的方案。该方案有利于基础制动装置的失效分析,可为城市轨道交通列车的安全运营提供参考。     

深入认识控制图和稳定性曲线图

JJF1033—2008《计量标准考核规范》于2008年9月1日起施行。新版的规范增加了运用控制图对测量过程进行统计控制的内容,并对计量标准的稳定性予以更全面的阐述,但是其中对稳定性曲线图却没有给出明确的表述。为此,剖析控制图与稳定性曲线图的联系,明晰了二者的特点和用途,以及在计量检定与校准过程中的作用。     

利用电感耦合等离子体原子发射光谱仪测定涂料中铅、镉、铬、汞含量的研究

通过实验方法、实验结果及对实验结果的讨论，介绍利用电感耦合等离子体原子发射光谱仪对涂料中铅、镉、铬、汞含量的最新测定方法及其可行性。     

城市轨道交通车站站区一体化设计

在对城市轨道交通车站站区空间形态特征及一体化设计中重点问题进行理论分析的基础上，通过宁波市轨道交通1号线行政中心站站区一体化设计方案，对地下空间的功能整合、一体化交通设计、地下空间环境设计等展开论述。     

Price of Bulk Carrier Seems to Hit Bottom

Bulk carrier has the biggest sustained volume in the global fleet,with an annual turnover of new ships exceeding 100m DWT between 2006～2010.Especially in 2007 when the market was at its peak time,new ship orders reached 170m DWT.After the financial crisis,demand for new ships plunged,and orders for new ships in 2011 were less than 40m DWT.In the first three quarters of 2012,only 13.1m DWT were ordered.Although the turnover of bulk carrier is still in the first place,it is not a comparison to the past.     

永字八法

永字八法是以“永”字的八笔（点、横、竖、钩、捺、仰横、长撇、短撇）为例，阐述毛笔正楷点画用笔的一种方法。     

船舶在密集通航区域航行时的正确避碰

随着港口的发展、建设带来了船舶的大型化,带来了船舶进出港的密度加剧,带来了更多的施工船舶,它们都在无形中增加了航道的压力,使得原本畅通的航道变得越来越拥挤.文章结合日常监督管理的实践,分析了造成航道不安全环境的主客观因素,论述了船舶在通航密集区域的正确避碰措施和监管措施.     

微表处应用子隧道路面的新型组合结构研究

鉴于我国对隧道路面结构和材料的研究比较薄弱而提出的隧道路面新的结构组合型式,即在贫混凝土基层水泥混凝土路面上加铺一层微表处,这对于提高路面使用性能有一定的帮助.