Real-world gaseous and particle emissions of a Bi-fuel gasoline/CNG Euro 6 passenger car

The objective of the present study is the assessment of the environmental impact of a bivalent (bi-fuel) vehicle, running either on gasoline or compressed natural gas (CNG). To that aim, a Euro 6 passenger car was tested under various real-world driving conditions. In order to cover the full range of conventional powertrains currently in the market, the tests were also repeated on a Euro 6 diesel passenger car. Both cars were driven in two routes, the first complying with the regulation limits and the second going beyond them. Carbon monoxide (CO), nitrogen oxides (NO_x) and particle number (PN) emissions were recorded using a Portable Emissions Measurement System (PEMS). Apart from the aggregated emission levels, in g/km, the exact emission location along the route was also assessed. Natural gas proved beneficial for CO and PN emissions, the level of which always remained below the respective legislation limits. On the other hand, under the dynamic driving conditions with gasoline, the relevant limits were exceeded. Cold start, occurring at the beginning of the urban part, and motorway driving were identified as major contributors to total emissions, especially in gasoline mode. However, the application of natural gas was associated with a penalty in NO_x emissions, which were significantly increased as compared to gasoline. Local peaks within the urban part were identified in CNG mode. In any case, the diesel vehicle was by far the highest NO_x emitter.     

Parking Spaces Repurchase Strategy Design via Simulation Optimization

Because of the rapid increase of vehicle numbers and land values, there is an increasing shortage in the supply of parking facilities in many cities. In many parking lots, residential drivers bought private parking spaces with high prices to ensure that they have spaces to park at any time. Recently, some parking lot operation companies plan to temporally repurchase a few private parking spaces back during certain time periods in a day and sell these places to public users to fully utilize the limited parking resources. How to choose the repurchase amounts and stopping time so as to maximize the profit then becomes an important problem. To solve this problem, a Gaussian mixture model is first proposed in this article to describe the time-varying arriving/departing behaviors of drivers and meanwhile the stochastic constraints of the profit maximization problem. Then, the expected optimal repurchase amounts and stopping time are estimated via simulation optimization. This new approach not only provides a useful statistical tool for parking spaces modeling but also overcomes several key limitations of current queuing based methodologies. Particularly, it emphasizes how to model drivers' behaviors on a small time-scale and explains the resulting benefits.     

VLCC货油舱横撑材优化布置

提要分析了VLCC货油舱横撑材结构的作用和受力特点,重点论述了VLCC货油舱横撑材的布置形式和优缺点,并对某型VLCC产品典型的货油舱横撑材布置方式做了优化,达到了减轻空船重量和方便船台施工的效果.     

Simulation and optimization: A short review

This review discusses some issues related to the use of simulation in transportation analysis. Potential pitfalls are identified and discussed. An overview of some methods relevant to the use of an advanced simulation tool in an optimization context is also provided.     

Assessing transportation user benefits with maximum trip lengths

Maximum time lengths of urban trips can be used to calculate major user benefits of transportation improvements. These benefits include those associated with reduced cost of travel, those associated with travel to additional destinations, and those associated with improved quality of destinations. Maximum trip lengths can be measured using techniques of psychological scaling.     

编制机车周转图的优化模型

指派问题算法模型和最小费用最大流模型是机车周转图优化的基本算法和模型,对解决部分双机牵引情况下的机车运用优化问题,具有一定的局限性。通过建立线性整数规划模型,可以解决铁路现场出现的列车运行图成对或不成对,列车单机牵引、全部双机牵引或部分双机牵引等多种情况下的机车周转方案的优化问题。为了简化求解过程,提高模型的实用性,在保持通用性的前提下,先后将整数规划模型转化为最小费用循环流和最小费用给定流模型。实际应用表明,最小费用给定流模型除了以上多种情况外,还可以解决客货分别勾画机车交路的优化运用问题。由于最小费用给定流模型具有很强的通用性,简化了程序设计工作,应用该模型并结合铁路实际情况开发的软件已在乌鲁木齐铁路局经过现场测试,使用情况良好。     

Optimization of nonlinear control strategy for anti-lock braking system with improvement of vehicle directional stability on split-μ roads

In a hard braking on a split-μ road, the achievement of shorter stopping distance while maintaining the vehicle in the straight line are of great importance. In this paper, to achieve these conflicting aims, an optimal nonlinear algorithm based on the prediction of vehicle responses is presented to distribute the wheel braking forces properly. The base of this algorithm is reducing the maximum achievable braking forces of one side wheels, as low as possible, so that the minimum stabilizing yaw moment is produced. The optimal property of the proposed control method makes it possible to get a trade-off between the shorter stopping distance and the less deviation of the vehicle heading from the straight line. The special case of this algorithm leads to the conventional anti-lock braking system (ABS) which generates the maximum braking forces for all wheels to attain the minimum stopping distance. However, the ABS cannot control the vehicle directional stability directly. The simulation results carried out using a nonlinear 8-DOF vehicle model demonstrate that the designed control system has a suitable performance to attain the desired purposes compared with the convectional ABS.     

PIV基准流场的评估分析

PIV基准流场是规范PIV流场测试技术和校验流场测试数据的统一标准。文章通过分析PIV流场测试技术的发展及其基准流场技术的发展状况,对PIV基准流场建设方法进行初步研究。应用CFD方法初步评估了HTA及ITTC的建议模型,给出了基准模型周围流场结果,并与HTA提供的SPIV试验测试结果进行比较分析,对PIV基准流场的方案设计和不确定度分析进行了进一步思考。分析结果为模型标准与测试标准的建设提供了基础。     

CTCS-2级列控系统地面应答器布置算法

简要介绍了既有线提速200km／h的CTCS-2级列控系统地面应答器布置规则，以及胶济线、浙赣线对此规则的工程运用。在此基础上，提出一个应答器合理布置的算法，阐述了该算法的实现过程。     

汽车燃油经济性优化方法

在环境和燃油资源的压力下，人们越来越多的重视汽车节油。文章从汽车燃油经济性的特点出发，通过大量的试验数据着重分析了整备质量和发动机排量对汽车燃油经济性的影响程度，通过对发动机特征的分析，介绍了改善发动机效率的方法，进而优化汽车的燃油经济性，同时从变速器和阻力2个方面分析了通过提高机械效率来改善燃油经济性的方法。结果表明，燃油经济性的优化是一个集轻量化、提高燃烧效率及改善机械效率的过程。