Reaction characteristics of the diesel oxidation catalyst of particulate matters from the diffusion flame of a oiler burner

The objective of this experimental study is to investigate the characteristics of the size distribution and the number concentration of PM (particulate matters) emitted from the diffusion flame of a boiler burner, which has the same type of combustion as a diesel engine. This study is performed to investigate the emission characteristics of nanoparticles generated from diffusion combustion in diesel fuel, and it considered fuel factors and the reaction characteristics of the nanoparticles on the DOC (Diesel oxidation catalyst). The factors examined in this experiment included the sulfur content in the fuel, the blend of the diesel fuel containing biodiesel and bio-ethanol, and the concentration of engine oil (0.1% and 1.0%) blended with diesel fuel. The particle size distribution of the nanoparticles exhausted from the boiler burner was measured by an SMPS (scanning mobility particle sizer). The number concentration of PM that were smaller than 70 nm in diameter greatly increased in the rear of the DOC when fuel containing 250 ppm of sulfur was used. The experiment also suggested that the particle number concentration in both the front and rear of the DOC was lower when ULSD (ultra low sulfur diesel) fuel blended with biodiesel and bio-ethanol, which are oxygenated fuels, was used than when only ULSD fuel was used. The higher the content of engine oil in the fuel, the higher the particle number concentration was in the front and rear of the catalyst. When the first dilution air temperature is increased from 30°C to 180°C, the nanoparticle number concentration dramatically dropped in the rear of the catalyst when fuel containing 250 ppm of sulfur was used, while the particle size distribution remained almost the same when the fuel with engine oil was used.     

地铁工程施工事故与风险管理

参考国际隧道协会所建议的分级系统,将2001-2006年间在亚太地区地铁工程施工期间所发生的43个事故,依其后果的严重性分级,以作为发展地下工程风险管理的基础.纳入考量的项目包括人员伤亡、经济损失及对民众生活的影响、工期的延误,以及对交通的影响.并以新加坡政府在尼诰大道灾变后所采取的一连串措施为例,列出地下工程风险管理的要素,勾画出地铁风险管理制度的基本架构.     

小型渔政船线型及附体设计优化

选取某近海小型渔政船典型船型,研究艏艉线型和附体对船舶阻力性能的影响.通过对线型、船型系数以及舭龙骨、压浪板、呆木等常规附体对小型渔政船航行性能的影响进行数值模拟分析,优化船舶线型,针对小型渔政船的功能需求选取合适的附体组合形式,并通过实船运行验证优化后的渔政船航行性能有所改善,达到预期目标,可为同型船舶设计提供参考依...     

我国农村物流网络节点体系发展思路

为服务乡村振兴战略实施、深入贯彻落实“四好农村路”建设精神,及时了解新时期我国农村物流网络体系的发展现状,探索农村物流网络节点建设的发展对策,通过实地调研、问卷调查、文献调查等调查方法以及指标对比分析法、分组分析法等统计方法,对农村物流网络节点的数量、分布规律及特点等进行了分析,对农村物流运输组织模式类别进行了划分,并总结了各模式下农村物流网络节点的特点。在此基础上,提出我国下一步推进农村物流网络节点发展的思路,认为构建我国农村物流网络节点体系应注重因地制宜,坚持“建管运”并举,促进物流服务与产业发展协同联动。     

钻孔灌注桩在富水砂性土层中的应用

钻孔灌注桩是一种常用的地基加固方法,如何有效控制灌注桩成孔后的稳定性,对于保证灌注桩整体成桩质量至关重要。以沿海地区某项目为例,针对长螺旋钻孔灌注桩在富水砂性土层施工中遇到的成孔效率低、孔底涌土等问题,提出了采用钻孔成孔后同步进行孔底注水的施工方法,并进行试桩验证。结果表明:孔底注水能有效地解决成孔后孔底涌土的问题。使用长螺旋钻孔灌注桩孔底注水技术既能降低工程造价,又能保证施工质量、发挥长螺旋钻机施工效率高的特点,具有良好的实用性。     

复杂环境下盐田港大型自动化集装箱港区集疏运体系布置

针对盐田港东作业区陆域形态不规则,西侧纵深狭小且后方为山体,对外交通体系集中且单一,港区水陆转运比例高的复杂环境特点,导致港区集疏运体系布置困难的技术问题。首先,通过分析比较和仿真模拟验证,结合盐田港区运营特点,提出二级进港闸口和三级出港闸口的多级智能闸口布置新模式,以进出合一的方式对接盐港东立交,并设置足够的缓冲空间,避免高架拥堵;其次,设置了穿越闸口区的专用匝道桥等多种方式的行政车辆通道,避免与集卡产生车流交叉;最后,选择合适区域设置中东专用通道,实现中、东作业区互联互通。通过上述布置方式较好地解决了盐田港东作业区的集疏运布置难题,提高港区交通服务水平。     

基于广义回归神经网络与遗传算法的玻璃钢渔船船型要素优化研究

利用神经网络的非线性拟合能力,建立了基于广义回归神经网络的\"船型要素-船体阻力\"数学模型,提高了模型的拟合精度。同时结合遗传算法的非线性寻优能力,利用改进的遗传算法完成了船型要素的优化设计。优化结果可以作为玻璃钢渔船初步设计的技术参考。     

降低感应电机直接转矩控制的转矩脉动的控制器

基于磁滞比较器和选择表的感应电机直接转矩控制(DTC),其开关频率可变,且转矩脉动大,特别在低速时.这是因为转矩和磁通的变化率以及转矩和磁通达到其上带和下带所花的时间随运行工况变化.文中提出了一种新型的开关频率固定的转矩控制器.新型控制器结构非常简单,其输出类似于传统的三点式磁滞比较器.就提出的控制器介绍了近似频域分析法,作为控制器参数选择的指南.介绍了感应电机直接转矩控制采用该转矩控制器进行的仿真和实验结果.结果表明提出的控制器可以保持开关频率恒定,并降低了转矩脉动,尤其在低速时.     

Machine learning applications in activity-travel behaviour research: a review

ABSTRACT

This paper reviews the activity-travel behaviour literature that employs Machine Learning (ML) techniques for empirical analysis and modelling. Machine Learning algorithms, which attempt to build intelligence utilizing the availability of large amounts of data, have emerged as powerful tools in the fields of pattern recognition and big data analysis. These techniques have been applied in activity-travel behaviour studies since the early ’90s when Artificial Neural Networks (ANN) were employed to model mode choice decisions. AMOS, an activity-based modelling system developed in the mid-’90s, has ANN at its core to model and predict individual responses to travel demand management measures. In the dawn of 2000, ALBATROSS, a comprehensive activity-based travel demand modelling system, was proposed by Arentze and Timmermans using Decision Trees. Since then researchers have been exploring ML techniques like Support Vector Machines (SVM), Decision Trees (DT), Neural Networks (NN), Bayes Classifiers, and more recently, Ensemble Learners to model and predict activity-travel behaviour. A large number of publications over the years and an upward trend in the number of published articles over time indicate that Machine Learning is a promising tool for activity-travel behaviour analysis and prediction. This article, first of its kind in the literature, reviews these studies and explores the trends in activity-travel behaviour research that apply ML techniques. The review finds that mode choice decisions have received wide attention in the literature on ML applications. It was observed that most of the studies identify the lack of interpretability as a serious shortcoming in ML techniques. However, very few studies have attempted to improve the interpretability of the models. Further, some studies report the importance of feature engineering in ML-based studies, but very few studies adopt feature engineering before model development. Spatiotemporal transferability of models is another issue that has received minimal attention in the literature. In the end, the paper discusses possible directions for future research in the area of activity-travel behaviour modelling using ML techniques.     

International cooperation against piracy: China's role,problems, and prospects

While there are some non-contentious issues about which states can cooperate, most must be molded around the demands of national interest. Piracy is a case where suppression would appear to be in the interest of all states; after all, pirates have been regarded as the enemies of all since Roman times. Despite this, states have often been more ambivalent as they have found piracy to be a useful cloak behind which to hide their wider geo-strategic ambitions. This paper notes that Somali piracy has attracted the interest of China whose citizens have been attacked and hijacked. It asks if this deployment demonstrates that China is committed to the protection of shipping in the context of the existing maritime order or if it has a wider purpose to advance Chinese interests in the Indian Ocean region.