Indoor air quality and passenger thermal comfort in Beijing metro transfer stations

In this study, particulate matter was investigated as the primary pollutant in the air quality of Beijing Metro transfer stations, and passenger thermal comfort during the transfer process was evaluated by using the relative warmth index (RWI). Passenger thermal comfort level is not ideal in 87% of the measured space and is slightly hot overall, with an RWI range of 0.20–0.43. Although 20% of the measured space has lower values than ASHRAE’s cooling comfort class, the thermal comfort level of most measured space is good in winter morning rush hours, with an RWI range from −0.18 to 0.28. The particulate matter (PM) concentration is related not only to the season and spatial depth but also to the transfer design of the metro station. During the morning rush period, the concentration ranges difference of PM₁₀ and PM_2.5 in winter are 262.9 μg/m³ and 125.5 μg/m³, respectively, which are 1.43 and 1.46 times higher than those of in summer. There are significant differences in the PM concentration and RWI values between the island and lateral platforms of Beijing Metro transfer stations, and the design of the lateral platform is superior to that of the island platform. Another exploratory experiment is conducted to determine if the PM concentration has a potential effect on human metabolic rate. The data in this paper provide a valuable reference for further comfort research and environmental control in metro station, and the conclusions may guide the further underground space design of metro transfer stations.     

高速铁路与公路客运竞争的市场分担率模型研究

随着高速铁路的快速发展,高速铁路网络初步形成,对公路客运也产生了巨大的冲击。在原有由经济性、快速性、方便性、舒适性、安全性因素组成的传统Logit函数上,加入偏好性因素,构建了改进的Logit函数模型来分析竞争市场分担率。同时,基于运行时速和距离,构建了高速铁路与公路客运市场分担率演变模型并进行了敏感性分析。结果表明,从市场总份额和影响因素重要性角度来讲,高速铁路与公路客运市场份额分别为53.32%和46.8%;从不同距离上的竞争演变角度来讲,在高速铁路时速分别为200、250、300、350 km时,高速铁路与公路客运竞争的市场临界点分别为200、150、100、75 km,大于这些临界点时,高速铁路市场份额占优势;小于这些临界点时,公路客运市场份额占优势。     

提高“轮机工程基础”考证通过率的探讨

文章针对航海院校轮机管理专业学生的三管轮适任证书考试,从把握考试大纲、熟悉教材和题库,多种方式相结合教学,系统复习、融会贯通和加强学生应试能力的训练四个方面论述了如何提高＂轮机工程基础＂课程的考证一次通过率。     

Strain rate sensitive steel constitutive models for finite element analysis of vessel-structure impacts

Civil infrastructure systems such as bridge piers, navigational guide walls, and protection structures that are located near navigable waterways are inherently at risk for being impacted by cargo vessels such as barges and ships. To safely design such systems to possess adequate vessel impact resistance, structural loads associated with potential vessel-structure collision conditions must be quantified in a conservative manner. While high-resolution finite element impact simulations may be employed to compute such loads, care must be exercised in defining the material characteristics of the vessel if conservative structural design loads are to be obtained. Importantly, constitutive relationships assigned to steel components in the vessel model must be capable of accounting for strain rate sensitivities and large-scale plastic deformations.In the present study, strain rate sensitive constitutive models were developed for two types of steel commonly utilized in marine construction in the United States—ASTM A36 and ASTM A1011. Tension tests were conducted over a wide range of strain rates (7.00 × 10⁻⁵ s⁻¹ – 250 s⁻¹) spanning from quasi-static to intermediate and high rates that are typically associated with vessel-structure impact events. A novel testing apparatus—employing an impact pendulum as an energy supply mechanism—was designed for this study to conduct intermediate to high-rate material testing. Features of the apparatus, discussed in this paper, overcome key problems encountered in other studies that have employed impact loading for tensile material testing. From the testing program, representative stress–strain relations and Cowper–Symonds strain rate sensitivity parameters were developed for the materials tested. Rate sensitivities of the two steel grades tested were found to be very similar to each other. Additionally, rate sensitivities from the present study agreed well with ultimate stress data measured in past studies of mild steel, but were found to be less rate-sensitive than yield stress data measured in past studies.     

不确定交通需求下交叉口信号配时区间优化模型

为解决混合交通流的不确定需求，合理描述不确定参数用以信号配时优化，本文提出交叉口信号控制配时参数区间优化模型。首先，以高峰时段5min采集标段数据，构造交通量区间，修正Highway Capacity Manual 2010(HCM2010)饱和流率计算公式，估计混合交通饱和流率区间；其次，构建信号配时参数区间非线性多目标规划模型，并以交叉口服务水平为性能目标，利用区间序关系与区间可能度模型进行转换，采用多层嵌套遗传算法求解；最后，以北京市道路等级相差较大的两相位与三相位交叉路口高峰时段数据为例，验证信号配时区间优化模型，并运用 VISSIM软件进行仿真比较。结果表明：本文所建模型可行、有效，且考虑饱和流率区间的信号配 时区间优化模型更适合于关键相位饱和流率波动较大的两相位信号交叉口，机动车平均延误和交叉口通行能力较Webster方法分别优化了35.9%和14.9%。     

基于卡尔曼滤波的交叉口排队长度实时估计模型

为解决现有排队长度估计方法不能对排队长度进行实时秒级估计的问题，本文采用车联网实时数据，构建基于卡尔曼滤波的实时排队长度估计模型。首先，以当前时刻加入和离开排队队列的车辆数为输入变量构建状态转移方程，以当前排队网联车的数量和渗透率构建观测方程；其次，采用回归模型估计状态转移方程和观测方程的噪声协方差矩阵；然后，提出基于卡尔曼滤波方法估计排队长度的流程算法和模型性能评价指标；最后，基于实际数据构建仿真环境验证模型的有效性。结果表明：当网联车渗透率为30％时，平均绝对误差(MAE)，平均绝对百分比误差 (MAPE)和均方根误差(RMSE)的平均值分别为1.6辆，20.9％和2.5辆；当渗透率大于20%时，与基准方法相比，本文模型估计效果更优。     

地铁车辆气密性影响因素及主要评价指标研究

随着城市的快速发展,部分城市对地铁车辆速度有了更高的要求,尤其是在国家促进城镇化发展的大背景下,市域(郊)铁路的发展、地铁车辆速度的提高使城镇居民出行更加便捷,如120 km/h的地铁车辆,其速度高、发车间隔短、换乘方便,但速度提高会带来其他方面的影响,如噪声、气密性等问题。文章研究地铁车辆气密性的评价标准、评价方法及影响因素,并提出气密性评价指标建议和提升气密性的技术措施。     

基于RISF融合的车辆横摆角速度估计

使用车载角速度传感器测量获得的横摆角速度,存在噪声干扰大、量测值滞后等问题.为了提高车辆横摆角速度估计的精确性,本文中设计了一种基于可靠指标传感器融合(reliability indexed sensor fusion,RISF)多源传感信息融合的估计算法.首先,使用自适应容积卡尔曼滤波算法对横摆角速度传感器量测值进行...     

影响公交分担率的关键因素研究

通过对2012年济南市居民出行意愿调查数据分析,建立全方式的多项选择Logit模型,并对影响公交分担率的关键因素(公交出行时间、步行时间、等车时间、公交票价、燃油费、停车费)进行分析,可为制定相关措施来提高公交分担率,缓解交通拥堵,实现"公交都市"建设目标提供有力支持。     

成渝通道客运市场竞争博弈分析

考虑博弈三要素,包括成渝通道客运市场博弈局中人、竞争策略集、益损值,建立博弈模型。根据市场分担率函数、成本变动函数构建赢得函数,采用非集计模型计算市场占有率,求得市场占有率与策略集的函数关系,研究博弈模型求解思路,并对博弈模型进行简化求解与分析,为通道客运市场的分析提供可靠方法。