Extracting patterns from Twitter to promote biking

Emphasis on non-motorized travel modes (for example, biking) reduces motorized trips and provides positive effects on the environment and the quality of human life. Understanding factors that influence people to biking or bike commuting can help decision makers, transportation planners, and bike commuting networks. Historically, conventional methods like surveys and crash data analyses were conducted to understand relevant factors. Survey and crash data analysis are difficult to perform in broad scale due to data availability and efforts. An innovative approach to determining these factors is to conduct social media mining to understand sentiments or motivations of bike commuters. People use terms (with hashtag at the beginning of the term) in Twitter, a popular social media network, to express their thoughts, activities or information. This study developed a framework for using Twitter data in understating the sentiments of the bikers with minimal effort. In this study, Twitter data associated with bike commuting hashtags were obtained for eight years (2009–2016). This study provided a framework of data collection and application of various natural language processing (NLP) tools (for example, text mining, sentiment analysis) to extract knowledge from the unstructured text data. Findings show that biking is associated with weather and seasonal patterns. The general sentiment towards biking is positive. However, negative sentiments are associated with bad weather, crime, and other challenges. The polarity scores indicate somewhat positiveness in the recent few years. The developed framework and the findings of this study will help planners and decision makers to promote biking on a broader scale.     

并联结构换热器模块中冷却空气流量的分配

为提高车辆换热器模块的匹配设计能力,针对冷却风在并联结构换热器模块中的流量分配进行数值模拟和试验研究。在计算中把复杂的翅片结构简化为多孔介质模型,并采用RNGk-ε湍流模型进行模拟。通过换热器模块的风洞试验对数值计算结果进行验证。结果表明由于各换热器的阻力特性不同,流量的分配与设计时的理想状态存在较大的差异,阻力小的换热器中风速高,相对流量变大。     

Social influences on household location, mobility and activity choice in integrated micro-simulation models

Agent-based approaches to simulating long-term location and mobility decisions and short-term activity and travel decisions of households and individuals are receiving increasing attention in land-use and transportation interaction (LUTI) models to predict land-use changes and travel behaviour in mutual interaction. Social interactions between households and between individuals potentially have an influence on a wide range of the long-term and short-term choices involved in these systems. In this paper we identify the areas in which social interactions play a role and address the question how these influences can be modelled in the context of agent-based LUTI models. We distinguish impacts on activity participation (joint activity participation, support-and-help activities) and impacts on decision making (information exchange, social adaptation of preferences and aspirations) as the two main areas of social influence. A prototype of a LUTI model is proposed that accounts for impacts of the social network on longer-term mobility decision making through information exchange and social adaptation of preferences and aspirations. The model is demonstrated in a numerical simulation.     

基于Fluent的空冷器管道系统流体均配研究

为了研究空冷器管道系统的流体均配问题,引入多孔介质模型,应用Fluent对空冷器的管道系统进行了数值模拟研究。结果表明:空冷器的压降越大,管道系统的流体分配越均匀;分流集合管与汇流集合管中的压力分布在一定程度上决定了管道系统的流体分配;分流集合管与汇流集合管中流体的流动方向相反有利于管道系统的流体均配,当二者的流体流动方向相同时,沿流动方向各支管流量依次增加。管道系统结构优化后,流体分配更均。     

Social welfare analysis of investment public–private partnership approaches for transportation projects

This paper has two objectives: (i) to introduce a new approach in order to gain widespread support for road pricing; and (ii) to develop a detailed social welfare analysis for road pricing schemes. We first describe our novel approach that stimulates public support for road pricing, which we refer to as an investment public–private partnership, or IP3. This approach returns a significant portion of the economic value created by road pricing back to the citizens who own the newly priced facility. We then present a social welfare framework that estimates the benefits and costs of using the IP3 approach on an urban transportation network. A P3 project’s impact on overall social welfare provides a more comprehensive evaluation criterion than the often-used Value for Money (VfM) analysis. Apart from several theoretical studies, a detailed social welfare analysis that includes all major P3 project stakeholders is absent from the literature. We use Fresno, California as our case study in order to conduct a welfare analysis on IP3s. Our results show that system-optimal tolling favors average users, but that government—and consequently taxpayers—should pay for costly tolling systems (negative profits). In contrast, unlimited profit-maximizing tolls raise substantial profits for government, for the infrastructure’s citizen-owners, and for the private sector, but the average user is worse off. From a social-welfare perspective, one should search for a Pareto improvement under which all major stakeholders are better off. Our estimates indicate that a mixed public and private tolling scheme offers such an improvement.     

离岸养殖装备网衣周围流场特性研究

为分析离岸养殖环境中网箱网衣在不均匀流速及不同流向下的水动力响应,采用多孔介质模型模拟网衣,针对完全对称方型网箱网衣,分析不均匀流速下网衣阻力及流场特性;针对非完全对称钻石型网箱网衣,在不均匀流速和不同流向下考察流场分布和阻力变化.结果显示,采用均匀流速进行模拟会使计算结果过于保守,流速随深度指数变化时的网衣阻力最大,它与线性变化时的网衣阻力差距小于20％;在90°～120°的流向下,网衣所受的总阻力较小,且流场衰减区域较小.研究可为钻石型网箱在实际海域中安置和方位的选择提供参考.     

基于全聚焦技术的高速列车空心车轴疲劳裂纹量化检测研究

空心车轴是高速列车重要的组成部分,目前主要使用常规超声技术从内孔面检测空心车轴外表面的横向疲劳裂纹,以保障高速列车运行安全。但使用常规超声技术无法实现疲劳裂纹的量化检测,从而无法评估空心车轴下次探伤周期,为列车安全留下隐患。文章研究了双层介质下超声最短传播路径的几何模型,结合Snell定律和Ferrari方法,计算出超声波束在双层介质交界面处的入射点位置,从而实现双层介质中的全聚焦方法成像。试验结果表明,该方法可以提供线性界面入射点坐标的精确解,并且可以准确地重建疲劳裂纹图像。通过增加路径计算和波形转换状态的二次反射来改进模型,可以实现空心车轴的真实裂缝量化成像。试验结果可以清楚地显示裂纹的形状和生长趋势,但裂纹尖端的漫反射现象仍会对裂纹的定量分析产生一定影响。     

路堤填石材料的振动压实特性研究

填石材料组成差异决定填石路堤物理力学性质差别较大,其压实受到材料自身和振动压路机参数等多种因素的影响,而振动碾压又使颗粒发生破碎,使得填石路堤的碾压变得更加复杂.因此,必须研究路堤填石材料的振动压实特性,以充分利用填石材料和振动压路机的性能,提高填石路堤的压实质量.将填石材料看成散体介质,通过分析其强度形成原理和建立2自由度振动压路机-填石系统模型,研究了压路机和填石材料之间力的相互作用关系,及其对填石材料压实的影响,并根据振动理论从不同角度给予解释.结果认为振动压路机的振动强度、颗粒惯性力是影响填石材料压实的主要因素,选择低频高幅振动压路机有利于填石材料的压实.     

块石路堤、护坡导热系数的实验研究

讨论了块石路堤、护坡试样在表面温度周期波动时自然对流产生的条件,分析了开放系统和封闭系统块石试样内部的热传输机理,以说明其热扩散系数和导热系数的确定方法。指出开放系统的试样由于传热形式不单一而不利于热扩散系数和导热系统的精确测定,而封闭系统试样内部的传热形式以热传导为主。结果表明,可用封闭系统的细长圆柱试样来测试路堤、护坡块石的热扩散系数和导热系数。     

谈谈艺术.自然.社会

艺术是同自然和社会紧密联系的。本文从艺术鉴赏角度出发,指出绘画艺术是一种形象思维与抽象思维相结合的社会的精神劳动产品,一种重要的社会现象。艺术对社会的批评方式恰恰是它的存在本身,是我们时代的投影和文化的隐喻和象征,能够永远表现着这个世界。艺术对于促进人类社会的历史发展具有一定的重要意义。