Spatial variation of roadside C2–C6 hydrocarbon concentrations during low wind speeds: Validation of CALINE4 and COPERT III modelling

The CALINE4 model is widely used to predict the effect of vehicle emissions on ambient concentrations close to roadways. It requires an evaluation of the rate at which different air pollutants are emitted by vehicles, taking into account things such as vehicle flow, velocity, type and age. For Europe the databases of the COmputer Program to calculate Emissions from Road Transport (COPERT) are combined with local vehicle details to obtain site-specific emission factors for dispersion modelling. The ability of CALINE4 to predict the spatial variation of hydrocarbon concentrations downwind of a motorway is assessed, as is the accuracy of COPERT III composite emission factors for several hydrocarbon compounds. The concentrations of seven traffic-associated compounds is found at three locations downwind and upwind of a motorway. Modelled and measured background-corrected downwind concentrations are compared on three bases: daily peak hour concentrations, mean concentrations, and a set of model evaluation parameters.     

Spatial variation of roadside C2–C6 hydrocarbon concentrations during low wind speeds: A note

This Note describes an investigation of spatial variations in the ambient concentrations of hydrocarbons in the vicinity of a suburban motorway during five consecutive weekday morning peak periods of unusually warm and calm conditions. Background-corrected downwind concentrations representing the influence of the motorway source were found to be strongly dependant on wind speed and direction. The ambient ethene-to-acetylene concentration ratio was greatest close to the roadside and the effect of wind speed on the ratio had different average profiles for main wind directions due to different rates of dispersal. Higher values were obtained using background-corrected concentrations.     

「台湾桃园国际机场联外捷运系统建设计划」地下工程的设计与施工

介绍「台湾桃园国际机场联外捷运系统建设计划」中机场区段地下工程的设计成果,并探讨施工时将面临的主要工程问题如,潜盾隧道穿越营运中的机场滑行道下方需考虑对其进行保护、隧道遭遇既有地锚的处理方式,及明挖覆盖隧道或车站于卵砾石层进行开挖,临时挡土措施及潜盾隧道的掘进作业,需考虑卵砾石大粒径与高硬度的特性等等设计考虑.现有数据显示,透过适当的机具改良、辅助工法的应用及良好的施工管理,即使是在高地下水压的卵砾石层,施作地下连续壁及以潜盾机施作隧道并无太大困难,且施工引致的地表沉陷及施工精度亦可获得良好的控制.     

曼谷的机场连接线

泰国曼谷市开始建设一条新线连接市中心和苏汪纳普机场，该工程总投资为250亿泰铢（6．75亿美元），预计2007年10月开通。     

巴黎恢复CDG快速线作为PPP项目

巴黎恢复了从市中心到戴高乐机场的快速轨道交通线，将它作为一个公私合作项目（PPP）来建设，预计2012年开通。     

Vehicle modeling with the exhaust system and experimental validation to investigate the exhaust vertical vibration characteristics excited by road surface inputs

An 8 degree-of-freedom (DOF) vehicle model is established to investigate the vertical vibration characteristics of an exhaust system excited by road surface inputs. The simplification of an exhaust system relevant to the vehicle model is discussed in detail, including the steps of exhaust modal analysis, definition of mass element, exhaust partitioning, parameter acquisition, and simplified exhaust validation. The vehicle model is developed based on a half-vehicle model, simulated using MATLAB/SIMULINK, and validated by comparing the simulation and experiment on various road profiles. Results show that the vehicle model effectively represents the dynamics of the vehicle characteristic in vertical vibration.     

Influence of nozzle hole diameter and orifice diameter on dme spray to get the similar heat value with diesel spray using the constant volume chamber

Low heating value (LHV) of di-methyl ether (DME) is lower than that of diesel. To get the similar heat value with diesel from the diesel engine operation, single injection quantity of DME should be increased. This investigation was tried to increase the injection quantity of DME by the modified diesel injector and investigated the penetration length and spray angle of DME spray. DME was injected by using three-type modified diesel injectors those nozzle-hole diameters (Injector 1: 1.66 mm, Injector 2 and 3: 0.25 mm) and orifice diameters were different (Injector 1 and 2: 0.6 mm, Injector 3: 1 mm). Spray characteristics of DME was investigated with a various ambient pressures (2.5, 5.0 MPa) in the constant volume chamber and a fuel was injected by varied injection pressure from 35 to 70 MPa by interval of 5 MPa using a DME common rail fuel injection system. The result shows that DME injection quantity by Injector 3 was 1.69 ~ 2.02 times larger than that of diesel injection quantity by Injector 1. In this case, DME spray got the similar heat value compared with diesel spray. The penetration speed of DME spray by Injector 3 was the fastest, thus when the spray development was end, the penetration length of DME spray by Injector 3 was the longest compared with the other cases. In case of the spray angle, Injector 2 and 3 had the similar spray angle and these were larger than that of diesel and DME sprays by Injector 1. As the result, Injector 3 was the solution for how to solve the low heating value of DME.     

Effect of mass ratio on hydrodynamic response of a flexible cylinder

The effect of the mass ratio on the flow-induced vibration (FIV) of a flexible circular cylinder is experimentally investigated in a towing tank. A Tygon tube with outer and inner diameters of 7.9 mm and 4.8 mm, respectively, was employed for the study. The tube was connected to a carriage and towed from rest to a steady speed up to 1.6 m/s before slowing down to rest again over a distance of 1.6 m in still water. Reynolds number based on the cylinder’s outer diameter was 800–13,000, and the reduced velocity (velocity normalized by the cylinder’s natural frequency and outer diameter) spanned from 2 to 25. When connected, the cylinder was elongated from 420 mm to 460 mm under an axial pre-tension of 11 N. Based on the cylinder’s elongated length, the aspect ratio (ratio of the cylinder’s length to outer diameter) was calculated as 58. Three mass ratios (ratio of the cylinder’s structural mass to displaced fluid mass, m*) of 0.7, 1.0, and 3.4 were determined by filling the cylinder’s interior with air, water, and alloy powder (nickel-chromium-boron matrix alloy), respectively. An optical method was adopted for response measurements. Multi-frequency vibrations were observed in both in-line (IL) and cross-flow (CF) responses; at high Reynolds number, vibration modes up to the 3^rd one were identified in the CF response. The mode transition was found to occur at a lower reduced velocity for the highest tested mass ratio. The vibration amplitude and frequency were quantified and expressed with respect to the reduced velocity. A significant reduced vibration amplitude was found in the IL response with increasing mass ratios, and only initial and upper branches existed in the IL and CF response amplitudes. The normalized response frequencies were revealed to linearly increase with respect to the reduced velocity, and slopes for linear relations were found to be identical for the three cases tested.     

Modeling the flow regime near the source in underwater gas releases

Recent progress in calculating gas bubble sizes in a plume, based on phenomenological approaches using the release conditions is a significant improvement to make the gas plume models self-reliant. Such calculations require details of conditions Near the Source of Plume (NSP); (i.e. the plume/jet velocity and radius near the source), which inspired the present work. Determining NSP conditions for gas plumes are far more complex than that for oil plumes due to the substantial density difference between gas and water. To calculate NSP conditions, modeling the early stage of the plume is important. A novel method of modeling the early stage of an underwater gas release is presented here. Major impact of the present work is to define the correct NSP conditions for underwater gas releases, which is not possible with available methods as those techniques are not based on the physics of flow region near the source of the plume/jet. We introduce super Gaussian profiles to model the density and velocity variations of the early stages of plume, coupled with the laws of fluid mechanics to define profile parameters. This new approach, models the velocity profile variation from near uniform, across the section at the release point to Gaussian some distance away. The comparisons show that experimental data agrees well with the computations.     

Modeling and solving discrete network design problem with stochastic user equilibrium

In this paper, we address the discrete network design problem, which determines the addition of new roads to existing transportation network to optimize the transportation system performance. Road users are assumed to follow the traffic assignment principle of stochastic user equilibrium. A mixed‐integer nonlinear nonconvex problem is developed to model this discrete network design problem with stochastic user equilibrium. The original problem is relaxed into a convex mixed‐integer nonlinear program, whose solution provides a lower bound of the original problem. The relaxed problem is then embedded into two proposed global optimization solution algorithms to obtain the global optimal solution of the problem. Copyright © 2016 John Wiley & Sons, Ltd.