养生作用对硫沥青性能影响分析

硫磺部分替代传统石油沥青用于道路工程建设可减少石油沥青用量,降低施工能源消耗,促进工业废渣中硫磺的回收利用,具有较高的经济和环保价值。为探究硫磺掺量（质量分数）及养生作用对硫沥青（SEA）性能的影响,采用差示扫描量热仪（DSC）验证硫沥青中硫磺的重结晶现象,对养生前后硫沥青的基本物理性能和黏度进行分析,并采用动态剪切流变仪（DSR）和弯曲梁流变仪（BBR）对养生前后硫沥青的流变特性和疲劳性能进行评价,最后借助荧光显微镜（FM）观察养生前、后硫磺在沥青中的微观分布特性。研究结果表明：养生后高硫磺掺量的硫沥青DSC曲线出现吸热峰,硫沥青（特别是高硫磺掺量下）的劲度有所增加,因此对硫沥青进行养生使其性能稳定后再进行相关性能评价更具现实意义;硫磺掺量较低（≤ 10%）时,硫磺主要以溶解硫的形式存在于沥青中起到软化沥青的作用,因此沥青的低温变形能力有所改善,但其高温抗变形能力有所降低;当硫磺掺量较高（≥ 35%）时,硫磺主要以重结晶的形式悬浮在沥青中使沥青变硬,在增加沥青高温抗变形能力的同时也牺牲了其低温抗裂能力;硫磺掺量较低时,硫沥青黏度随着硫磺掺量的增加而降低;硫磺掺量较高时,硫沥青90℃和105℃黏度随着硫磺掺量的增加而增加,但硫沥青120℃和135℃黏度相差不大,同时硫磺加入最高可降低沥青的施工温度达20℃;线性振幅扫描（LAS）试验结果表明,养生后的硫沥青疲劳寿命比基质沥青长,其中35%硫沥青疲劳性能最佳;硫磺掺量进一步增加,硫沥青疲劳寿命缩短至与基质沥青相近;FM分析表明,硫磺掺量不高于5%时,硫磺全部溶解于沥青中,且养生后硫磺未重结晶,相应硫沥青无荧光性;硫磺掺量高于5%时,硫磺在沥青中分布均匀,养生后10%硫沥青中硫晶斑尺寸和面积显著增大,高硫磺掺量硫沥青中硫晶斑面积仅略有增加。     

Evaluation of alternative battery technologies for a solar assist plug-in hybrid electric tractor

This paper looks at the various battery technologies available for use in solar assist plug-in hybrid electric tractors In this context, solar assist plug-in hybrid electric tractors are those that may be used in light-duty agricultural operations. To determine the most suitable battery, four common technologies are analyzed looking at the environmental life-cycle effects and costs.     

Outsourced probe data effectiveness on signalized arterials*

ABSTRACT

This paper presents results of an I-95 Corridor Coalition sponsored project to assess the ability of outsourced vehicle probe data to provide accurate travel time on signalized roadways for the purposes of real-time operations as well as performance measures. The quality of outsourced probe data on freeways has led many departments of transportation to consider such data for arterial performance monitoring. From April 2013 through June of 2014, the University of Maryland Center for Advanced Transportation Technology gathered travel times from several arterial corridors within the mid-Atlantic region using Bluetooth traffic monitoring (BTM) equipment, and compared these travel times with the data reported to the I95 Vehicle Probe Project (VPP) from an outsourced probe data vendor. The analysis consisted of several methodologies: (1) a traditional analysis that used precision and bias speed metrics; (2) a slowdown analysis that quantified the percentage of significant traffic disruptions accurately captured in the VPP data; (3) a sampled distribution method that uses overlay methods to enhance and analyze recurring congestion patterns. (4) Last, the BTM and VPP data from each 24-hour period of data collection were reviewed by the research team to assess the extent to which VPP captured the nature of the traffic flow. Based on the analysis, probe data is recommended only on arterial roadways with signal densities (measured in signals per mile) up to one, and it should be tested and used with caution for signal densities between one and two, and is not recommended when signal density exceeds two.