Dependence patterns associated with the fundamental diagram： a copula function approach

Randomness plays a major role in the interpretation of many interesting traffic flow phenomena, such as hysteresis, capacity drop and spontaneous breakdown. The analysis of the uncertainty and reliability of traffic systems is directly associated with their random characteristics. Therefore, it is beneficial to understand the distributional properties of traffic variables. This paper focuses on the dependence relation between traffic flow density and traffic speed, which constitute the fundamental diagram （FD）. The traditional model of the FD is obtained essentially through curve fitting. We use the copula function as the basic toolkit and provide a novel approach for identifying the distributional patterns associated with the FD. In particular, we construct a rule-of-thumb nonparametric copula function, which in general avoids the mis-specification risk of parametric approaches and is more efficient in practice. By applying our construction to loop detector data on a freeway, we identify the dependence patterns existing in traffic data. We find that similar modes exist among traffic states of low, moderate or high traffic densities. Our findings also suggest that highway traffic speed and traffic flow density as a bivariate distribution is skewed and highly heterogeneous.     

Influence of baffle position on liquid sloshing during braking and turning of a tank truck

The influence of baffle position on liquid sloshing during the braking and turning of a tank truck was studied using a volume of fluid (VOF) model. The forces,their positions and weight distribution during braking and the forces and rolling moment during turning were calculated. The reliability of the calculation method was validated by comparisons with experimental results. The results showed that during braking,liquid splashes in the tank and the maximum forces and G (the ratio of weight acting on the front axle to the rear axle) are large when A (the ratio of the arch area above the baffle to the area of cross section)≤0.1. When A≥0.2,as the position of the baffle is lowered,the maximum of Fx (the force in direction x) first decreases then increases,and the maximum of Fy (the force in direction y) and G increase. During turning,liquid splashes in the tank and the maximum forces and M (the rolling moment) are large when D (the ratio of the arch area above the baffle to the area of cross section)≤0.2. When D≥0.3,as the position of the baffle is lowered,the maximums of Fy,Fz (the force in direction z) and M increase.     

谈项目的组织与管理

现代项目管理是一门综合的学科,是通过对项目方方面面的协调管理,而促进项目达到预期目标的管理手段,是通过管理人来做成事的方法论。现代项目管理所谈及的项目,是广义的项目,它涉及的范围非常广泛。     

我国企业现金流管理问题及对策探析

现金流量管理是企业财务管理的重要组成部分,顺畅的现金流是企业可持续经营的重要保障和有力支撑,因此,确立现金流管理在企业财务管理中的核心地位,将有效避免以利润为核心的管理给企业所带来的不利影响。我国加强企业现金流管理应采取以下措施：一是整合现金流与利润流管理,使二者趋向统一;二是建立操作性强的现金流管理体系,全方位管理企业的现金流;三是强化对现金流量的预算管理;四是完善现金流管理的监督机制;五是建立企业内部现金流管理模型。     

基于工作过程的“电子商务外贸流程”课程改革

本文针对当前高职电子商务外贸流程课程的发展现状和存在的问题,运用基于工作过程的课程开发模式,提出电子商务外贸流程课程的改革思路与措施。     

润滑材料和技术的研究进展

分析和探讨近年来在润滑材料和润滑技术方面的研究进展。润滑材料方面有绿色润滑油、离子液体、液晶润滑以及固体添加剂在润滑脂中的应用等;润滑技术方面有纳米润滑技术、颗粒流润滑技术和油雾润滑技术等。     

农村职业教育与劳动力有序转移初探

农民问题是“三农”问题的核心。我国是一个农业大国,随着科学技术、社会经济的迅速发展,出现了农村劳动力就业不充分或劳动力过剩现象。发展农村职业教育,解决农村劳动力转移问题是保持农民收入持续稳定增长的关键。解决农村劳动力转移问题是时代的要求,农民的呼唤,是各级政府及相关部门义不容辞的责任和义务。     

人才跨国流动剖析

文章论述当前人才跨国流动的特征和动向,分析发达国家逐步放宽人才移民政策、招收并挽留外国留学 生、承认人才的双重国籍、设立国家猎头挖取人才、利用跨国公司引进与使用人才、开展国际科技合作与交流、建立 海外人才联络机构、成立国家风险基金与担保计划等吸引海外人才的主要措施,并以此为借鉴,提出我国吸引海外高 端人才来华（回国) 创业的政策建议。     

基于ANSYS的焊接模拟技术应用及分析流程

ANSYS软件强大的热分析功能为焊接模拟分析提供了平台,尤其是参数化设计APDL语言的应用为焊接模拟关键技术的实现提供了条件。文章论述了ANSYS环境下焊接的模拟与分析各主要环节的实现方法 ,并归纳给出了ANSYS环境下焊接模拟和参数优化设计的完整流程,为深入研究ANSYS环境下的焊接模拟与分析打下基础。     

求解最小费用流问题的蚁群算法

为了运用蚁群算法解决最小费用流问题,首先结合有向网络描述了最小费用流数学模型,运用从终点向始点反向计算的思想求解在最大可行流约束下的最小费用,然后给出了其具体过程.最后通过仿真实验,调整圈法和标号算法验证表明：该算法是有效可行的.