A stochastic multimodal reliable network design problem under adverse weather conditions

This paper formulates a network design problem (NDP) for finding the optimal public transport service frequencies and link capacity expansions in a multimodal network with consideration of impacts from adverse weather conditions. The proposed NDP aims to minimize the sum of expected total travel time, operational cost of transit services, and construction cost of link capacity expansions under an acceptable level of variance of total travel time. Auto, transit, bus, and walking modes are considered in the multimodal network model for finding the equilibrium flows and travel times. In the proposed network model, demands are assumed to follow Poisson distribution, and weather‐dependent link travel time functions are adopted. A probit‐based stochastic user equilibrium, which is based on the perceived expected travel disutility, is used to determine the multimodal route of the travelers. This model also considers the strategic behavior of the public transport travelers in choosing their routes, that is, common‐line network. Based on the stochastic multimodal model, the mean and variance of total travel time are analytical estimated for setting up the NDP. A sensitivity‐based solution algorithm is proposed for solving the NDP, and two numerical examples are adopted to demonstrate the characteristics of the proposed model. Copyright © 2014 John Wiley & Sons, Ltd.     

Energy Consumption Analysis of Different Bev Powertrain Topologies by Design Optimization

Flexible layout of electric motors in battery electric vehicles (BEVs) has enabled different powertrain topologies to be used. However, these different powertrain topologies also affect the overall efficiency of energy conversion from the electrochemical form stored in the battery to the mechanical form on the driving wheels for vehicle propulsion. In this study, a methodology combining an energy-based BEV simulation model with the genetic algorithm optimization approach is applied to evaluate the energy efficiency of three different BEV powertrain topologies. The analysis is carried out assuming two different urban driving conditions, as exemplified by the New European Drive Cycle (NEDC) and the Japanese JC08 drive cycle. Each of the three BEV powertrain topologies is then optimized – in terms of its electric motor size and, where applicable, gear reduction ratio – for minimum energy consumption. The results show that among the three powertrain topologies, the wheel-hub drive without gear reducers consumes the least energy. The energy consumption of BEVs under the more aggressive JC08 drive cycle is consistently 8 % above that under NEDC for all three powertrain topologies considered.     

Experimental investigation of wing-in-ground effect with a NACA6409 section

The aerodynamic characteristics of NACA6409 in the vicinity of the ground were experimentally studied in a wind tunnel. Lift and drag forces, the pitching moment, and the center of pressure were measured with respect to various major aerodynamic parameters, such as the ground clearance, the angle of attack, the aspect ratio (AR), and the endplate type, which resulted in a total number of 420 conditions. In addition, a smoke trace test was conducted to visualize the flow pattern around NACA6409 in the vicinity of the ground. As a result of the ground effect and the influence of the endplate, the lift-to-drag ratio increased at low ground clearance and the center of pressure moved forward to the leading edge; that is, the endplate and ground effects were equivalent to the aerodynamic advantage that results from increasing the AR of the wing. Extended experimental results are useful for understanding the aerodynamic characteristics influenced by each aerodynamic parameter during ground effect as well as for verifying numerical simulation.     

一种神经元振荡器网络的快速同步算法

设计了一种新的神经元振荡器网络快速同步学习算法，该算法能保证同组的振荡器达到完全同步，同时，采用相位延迟方法，使不同图像目标的振荡器组的相位延迟正比于其在空间上的蹑度，实现目标对象的分离与提取。     

Simulation Study on Thermal Management Strategy to Achieve 99 % SCR Efficiency of a Heavy-Duty Diesel Engine over a Transient Cycle

In this study, NOx conversion characteristics of a urea selective catalytic reduction (SCR) system equipped on a heavy-duty diesel engine were evaluated through engine dynamometer bench tests over a scheduled world harmonized transient cycle (WHTC). Also, based on transient SCR simulations, the thermal management strategy to improve SCR NOx conversion efficiency was investigated. As a result, it was found that a selective increase in exhaust temperature at low temperature period would be a useful measure to increase SCR efficiency on WHTC mode. From the baseline SCR efficiency of around 98 % on WHTC mode, the current simulation results have shown that around 99 % level of SCR efficiency would be achievable by increasing exhaust temperatures with modifying diesel exhaust fluid (DEF) dosage. Another valuable contribution of this study is that the design guidelines for controlling exhaust temperature and DEF injection to obtain a target NOx conversion efficiency are presented for SCR systems of heavy-duty diesel engines on transient operating conditions.     

城市交通机动化进程及影响因素研究

面对中国大城市不断加快的机动化进程及其产生的一系列问题,探讨了城市机动化的发展趋势及影响因素。首先提出城市交通机动化进程的两个标志,并进一步总结城市交通结构的演变特征。然后分析了城市经济发展水平、人口密度、道路设施和公共交通发展对机动化发展的影响,据此判断城市机动车保有量仍将保持高速增长态势。最后指出,小汽车交通模式一旦在大城市形成,短期内难以改变,大城市应根据自身特点发展公共交通并采取相应的交通管理措施引导小汽车合理使用,不断优化交通结构。     

A Framework for Developing Driving Cycles with On‐Road Driving Data

Abstract

This paper attempts to propose a framework on driving cycle development based on a thorough review of 101 transient driving cycles. A comparison of the driving cycles highlighted that Asian driving is the slowest but most aggressive while European driving is the fastest and smoothest. Further review of the cycle development methodologies identified three major elements for developing a driving cycle; test route selection, data collection and cycle construction methods. A framework was eventually proposed based on these findings and recommendations from this review. First, traffic activity patterns and quantitative statistics should be considered in determining the test routes. Speed data can be collected by using chase car method, on‐board measurement techniques or their hybrid. As for the construction of driving cycle, the matching approach has been more commonly used. It is recommended that the tendency of zero change in acceleration, which has been commonly ignored in the literature, and the application of succession probability at second‐by‐second level should be further explored. A fifth mode, creeping, is also recommended for modal analysis for characterizing urban congested driving conditions.     

A study on slamming pressure on a flat stiffened plate considering fluid–structure interaction

Normally, the design slamming pressure on the bottomof a semi-submersible-type floating rig is determined in a simple way using the relative speed obtained from an air-gap analysis. However, few studies have taken a thorough, robust, and deep-background approach to the estimation of design pressure. To investigate the slamming pressure on the bottom of a semi-submersible rig, a simplified deformable stiffened plate of a zero-degree deadrise angle is simulated using the nonlinear FEM software LS-DYNA, which can take the influence of fluid–structure interaction (FSI) into account. Various parametric studies are carried out to examine the effects of structural flexibility, coupling stiffness, mesh size, velocity, stiffener size, and air cushion. The pressure response on the plate by the coupling of fluid and structure is studied and the FSI effect of each parameter is discussed. Then, equivalent transient and static loads that result in the same maximum or permanent deformation as FSI are evaluated for design purposes through a series of parametric studies.     

Assessing carbon reduction effects toward the mode shift of green transportation system

Plans are underway to introduce green transportation systems at Taiwan's famous scenic spot, Sun Moon Lake, to reduce carbon emissions. Carbon reduction effects after changing the current lake tour modes are assessed using a nested logit model with a stated preference survey, which investigated tourists' choice preferences. The empirical results reveal that the modes of electric bus, electric vehicle sharing, and bike are clustered in the same competitive group. Travel cost, in‐vehicle travel time, and out‐vehicle travel time are found to be statistically significant with the expected negative effects. In particular, the attribute of carbon reduction is only significant for green tourists, who are willing to pay US$ 3.5/kg of carbon saved. The result indicates that more efficient carbon reduction is possible by restricting the usage of gasoline vehicles rather than improving the service levels of low‐carbon modes. Notably, the effect of parking charges on emission reduction is equal to the amount of carbon dioxide absorbed by 4511 trees per day. Copyright © 2016 John Wiley & Sons, Ltd.     

数字狂徒

从21世纪开始,我们就半自愿半被迫地被推进数位的世界,一切原本连绵温暖的东西忽然间被分断成疏离的存在,菲林、黑胶唱片、信件等都被电脑里一连串的零一零一零一数字取代。芸芸众生之中,唯一不被数码攻陷的,便是高级腕表的世界。在这里,如果你戴着一枚数码跳字腕表,是会惹来鄙夷目光的。