新型氯离子扩散系数检测方法的应用研究

目前对混凝土的质量检测从强度向耐久性等多面发展，在耐久性的检测中以抗氯离子渗透为主，用NEL法检测氯离子扩散系数是一种新型的且正为广大科研及检测单位所接受的检测手段，通过试验前的准备、样品的制备及试验中的注意点等几方面阐述在用此法检测时应注意的几个要点，以提高检测的精确度。     

Singularly perturbed differential-difference reaction diffusion equations with time delay

A class of differential-difference reaction diffusion equations with a small time delay is considered. Under suitable conditions and by using the method of the stretched variable, the formal asymptotic solution is constructed. And then, by using the theory of differential inequalities the uniformly validity of solution is proved.     

盾构隧道壁后注浆试验与浆液扩散机理研究进展

盾构隧道壁后注浆具有控制地层变形、确保管片受力均匀等作用,但壁后注浆施工中也常出现隧道上浮、管片破损、螺栓剪断等现象,壁后注浆效果与注浆施工参数的控制密切相关。为达到预期注浆效果,深入研究壁后注浆过程中浆液的扩散机理,提出合理的壁后注浆施工控制策略具有重要现实意义。基于目前国内外学者在盾构隧道壁后注浆浆液扩散机理方面所开展的工作,从现场实测、模型试验、理论分析3个方面进行梳理总结,分析现有研究的进展和不足。在现场实测方面,目前常用的监测手段是探地雷达无损检测法和埋设仪器法;室内模型试验包括整体模型试验和局部模型试验,整体模型试验主要用于模拟盾构掘进过程中的同步注浆施工,局部模型试验主要用于分析浆液固结变形以及压力消散过程;在理论分析方面,当前主要从盾尾间隙特征、浆液流体特性以及浆液-土体相互作用机理研究浆液扩散过程,浆液扩散过程可概括为充填、渗透、压密和劈裂4个阶段,充填注浆浆液的扩散模型主要是环形充填扩散和扇形充填扩散,渗透注浆浆液的扩散模型有球面渗透扩散和柱面渗透扩散,压密注浆浆液的扩散模型有球形压密扩散和柱形压密扩散,劈裂注浆过程很少考虑;在数值计算方面主要侧重于研究盾构壁后注浆对管片受力和地表沉降的影响。最后,分别从盾构隧道断面形式、理论模型的地层适应性、统一扩散理论模型、浆液扩散微观机理等方面展望了盾构隧道壁后注浆浆液扩散机理研究的发展趋势。     

高响应性空燃比传感器的开发

作为汽车发动机控制系统的主要部件,空燃比传感器的响应性对燃油喷射控制的影响很大.为提高空燃比传感器的响应性,分别通过数值模拟和试验,对传感器感测元件的性状进行了研究.结果表明,感测元件的扩散层对传感器响应时间的影响最大,使用5～1Oμm孔径的多孔固体并增加其孔隙率,可在保证温度稳定性的同时提高其响应性.     

Who will buy electric vehicles? Identifying early adopters in Germany

Electric vehicles (EVs) have noteworthy potential to reduce global and local emissions and are expected to become a relevant future market for vehicle sales. Both policy makers and car manufacturers have an interest to understand the first large EV user group, frequently referred to as ‘early adopters’. However, there are only a few empirical results available for this important group. In this paper, we analyse and discuss several empirical data sets from Germany, characterising this user group from both a user and a product perspective, i.e. who is willing to buy an EV and who should buy one. Our results show that the most likely group of private EV buyers in Germany are middle-aged men with technical professions living in rural or suburban multi-person households. They own a large share of vehicles in general, are more likely to profit from the economical benefits of these vehicles due to their annual vehicle kilometres travelled and the share of inner-city driving. They state a higher willingness to buy electric vehicles than other potential adopter groups and their higher socio-economic status allows them to purchase EVs. In contrast to this, inhabitants of major cities are less likely to buy EVs since they form a small group of car owners in general, their mileage is too low for EVs to pay off economically and they state lower interest and lower willingness to pay for EVs than other groups. Our results indicate that transport policy promoting EVs should focus on middle-aged men with families from rural and sub-urban cities as first private EV buyers.     

基于多折线外特性模型的直流牵引供电系统稳态短路计算

直流牵引供电网络故障分析对城市轨道交通牵引供电系统设计有着重要的作用.针对整流机组,采用多段折线的外特性模型,使用变化理想电压源、内阻的戴维南等效电路模拟,并通过迭代的方法确定短路时的工作区间.建立了包括杂散电流收集网在内的供电系统仿真模型,可较准确地仿真短路时各整流机组负荷以及接触网、钢轨与杂散电流收集网电位等的变化情况.     

α—γ系爆炸焊接复合板加热后碳迁移规律

对α－γ系爆炸焊接复合板加热后碳迁移引起的增碳层宽度的变化规律进行了研究，得出了增碳层宽度的变化与Ｔ和t关系的数学模型，该模型的试验结果与试验数据有良好的一致性。     

现场测试混凝土抗氯离子渗透性方法的应用研究

为快速、准确地测定混凝土中氯离子的含量,以实现对混凝土耐久性的有效评价和钢筋腐蚀的适时防护与有效修复,研究现场测试氯离子渗透性的方法是非常必要的。结合客运专线工程施工情况,分别按矿物掺合料不同掺量以及不同的强度等级进行配合比设计试验,采用PERMIT离子迁移仪对混凝土试件进行氯离子扩散系数的测定,并采用电通量法进行验证。结果表明：随着电通量的增加,氯离子扩散系数呈现增加的趋势,二者存在很好的线性关系;双掺粉煤灰＋矿粉的混凝土抗氯离子侵入性优于单掺粉煤灰的混凝土;PERMIT离子渗透试验方法测得的试验结果准确可靠,具有很强的实用性。可以为混凝土耐久性的判定提供依据。     

基于信息扩散理论的浙江通航环境风场风险分析

以浙江省各气象观测站风场数据为基础,根据信息扩散理论分析了浙江省及其沿海地区最大风速、大风天数的风险概率及其空间分布.研究表明:浙江内陆大部分区域10a一遇最大风速为15～20m/s,中部沿海为30～40m/s;7～9月是沿海大风发生风险概率较高的月份,嵊泗站冬夏季节9级以上大风概率较低,春秋季节风险概率较高;7级以上大风6d/月和12d/月的风险概率有比较明显的季节性;嵊泗站在春季、大陈岛站在10月至次年3月相比其他月份风险概率较高.     

自动变速器技术状况对稳态工况法检测的影响分析

基于稳态工况法特点和自动挡车辆排气污染物超标现状,分析了自动变速器技术状况对稳态工况法检测的影响,指出在排气污染物超标车辆治理实践中应注重自动变速器的检查与性能恢复,对制定针对性的预防和治理措施具有指导意义。