一种改进的Jakes’信道模型及仿真

由于无线通信环境中存在的诸多不确定因素以及其在现代无线通信系统中的重要作用，合理的无线信道成为通信系统仿真研究的重要目的。确立信道仿真模型的目的就是为了尽可能的得到实际信道的统计特性，该文针对Jakes提出的信道模型，通过仿真来分析其局限性，并参考其中的谐波叠加（sum of sinusoids，SOS）法，来建立一种采用了随机分支增益、随机初始相位和有条件的随机多普勒频率改进的信道模型。     

复合地层盾构机推进速度SVM预测模型研究

在复合地层盾构法隧道施工中,如何提高盾构机推进速度一直是盾构机设计、施工人员研究的重点。以长沙轨道交通1号线五一广场到营盘路隧道工程为研究背景,现场采集盾构机掘进参数,应用SVM,建立了"五营"区间复合地层盾构机推进速度的预测数学模型,并对模型进行检测,检测结果表明该预测模型对推进速度预测的平均相对误差≤7%,验证了该模型对推进速度预测的有效性。     

Are HOV/eco-lanes a sustainable option to reducing emissions in a medium-sized European city?

Innovative traffic management measures are needed to reduce transportation-related emissions. While in Europe, road lane management has focused mainly on introduction of bus lanes, the conversion to High Occupancy Vehicles (HOV) and eco-lanes (lanes dedicated to vehicles running on alternative fuels) has not been studied comprehensively. The objectives of this research are to: (1) Develop an integrated microscopic modeling platform calibrated with real world data to assess both traffic and emissions impacts of future Traffic Management Strategies (TMS) in an urban area; (2) Evaluate the introduction of HOV/eco-lanes in three different types of roads, freeway, arterial and urban routes, in an European medium-sized city and its effects in terms of emissions and traffic performance. The methodology consists of three distinct phases: (a) Traffic and road inventory data collection; (b) Traffic and emissions simulation using an integrated platform of microscopic simulation; and (c) Evaluation of scenarios. For the baseline scenario, the statistical analysis shows valid results. The results show that HOV and eco-lanes in a medium European city are feasible, and when the Average Occupancy of Vehicles (AOV) increases, on freeways, the majority of vehicles can reduce their travel time (2%) with a positive impact in terms of total emissions (−38% NO_x, −39% HC, −43% CO and −37% CO₂). On urban and arterial corridors, the reduction in emissions could be achieved only if the AOV increases from 1.50 to 1.70 passengers/vehicle. Total emissions of the corridor with an AOV of 1.70 passengers/vehicle can be reduced up to 35–36% for the urban route while the values can be reduced by 36–39% for the arterial road. With the introduction of Hybrid Electric Vehicles (HEV) and Electric Vehicles (EV) it is possible to reduce emissions, although the introduction of eco-lanes did not show significant reductions in emissions. When both policies are simulated together, an emissions improvement is observed for the arterial route and for two of the scenarios.     

Sensitivity-based uncertainty analysis of a combined travel demand model

Travel demand forecasting is subject to great uncertainties. A systematic uncertainty analysis can provide insights into the level of confidence on the model outputs, and also identify critical sources of uncertainty for enhancing the robustness of the travel demand model. In this paper, we develop a systematic framework for quantitative uncertainty analysis of a combined travel demand model (CTDM) using the analytical sensitivity-based method. The CTDM overcomes limitations of the sequential four-step procedure since it is based on a single unifying rationale. The analytical sensitivity-based method requires less computational effort than the sampling-based method. Meanwhile, the uncertainties stemming from inputs and parameters can be treated separately so that the individual and collective effects of uncertainty on the outputs can be clearly assessed and quantified. Numerical examples are finally used to demonstrate the proposed sensitivity-based uncertainty analysis method for the CTDM.     

应用广义最大覆盖模型进行公路养护应急中心布局选址研究

应用广义最大覆盖模型方法在江西省国省道公路网络中进行公路养护应急中心布局选址,将养护应急中心设置在县级及以上行政中心点上,在点的服务半径已知的条件下,求解如何设立数量最少的点便可覆盖所有区域.     

一种定制型铁路信号监测系统的设计与实现

针对铁路信号业务模式不断变化的特点,设计一种业务定制型铁路信号监测系统,通过提供信号基础元素库及图形化的构建过程,实现铁路信号监测业务的灵活定制。     

桩-土作用在大型旅客站房基础设计中的应用

当大型旅客站房基础与地下出站通道重叠时,由于地下出站通道刚度大、结构超长,且属半露天地下结构,对温度作用变化明显,利用传统的刚性固结模型对站房基础进行设计时较难得到合理的结果或造成巨大的浪费。论述桩-土作用机理的复杂性,并对桩-土作用力学模型进行分析。通过分布弹簧模型对旅客站房在温度作用下的结构内力进行分析,并与刚性固结模型计算结果进行对比,得出旅客站房基础设计考虑桩-土作用的合理化计算模式。     

(Unintended) Transport impacts of an energy-environment policy: The case of CNG conversion of vehicles in Dhaka

Motor vehicles are one of the major sources of air pollution in Dhaka, the capital of Bangladesh. The government took various policies to convert the petroleum vehicles on road to run on compressed natural gas (CNG), which allows both air quality improvements and energy security benefits. One of the market friendly policies to encourage the fuel switch was to increase the price differential between CNG and petrol and diesel. This has allowed a wide-scale adoption of CNG as the fuel of choice. However, several years into the policy, there is now a widespread belief among the policymakers that the CNG conversion may have increased car ownership and car travel due to their lower running costs, resulting in more congestion and a reversal of the strategy is on the cards. It is therefore important to test the hypothesis whether CNG conversion had genuinely increased car ownership and car travel in Dhaka city. This paper presents the results of a questionnaire survey and an econometric intervention analysis to understand the impact of CNG conversion on car ownership and car travel in Dhaka. Attention is also given to disentangle the self-selection and price-induced travel effects of CNG conversion. Results show that ownership did not increase, but travel of on-road vehicles increased due to the CNG policy. However, additional congestion costs are still around one half of the health benefits brought about by the policy.     

Multi-objective optimization of train routing problem combined with train scheduling on a high-speed railway network

Based on train scheduling, this paper puts forward a multi-objective optimization model for train routing on high-speed railway network, which can offer an important reference for train plan to provide a better service. The model does not only consider the average travel time of trains, but also take the energy consumption and the user satisfaction into account. Based on this model, an improved GA is designed to solve the train routing problem. The simulation results demonstrate that the accurate algorithm is suitable for a small-scale network, while the improved genetic algorithm based on train control (GATC) applies to a large-scale network. Finally, a sensitivity analysis of the parameters is performed to obtain the ideal parameters; a perturbation analysis shows that the proposed method can quickly handle the train disturbance.