Modelling the impact of double hull technology on oil spill numbers

This article presents the results of modelling the behaviour of oil spill numbers published by the International Tanker Owners Pollution Federation over the period 1970 to 2005. Poisson count or negative binomial models are estimated to identify the major determinants of oil spill numbers over this period. The results are used to estimate the number of oil spills that would have occurred in the absence of the adoption of double hull technology. Other potential factors, such as changes in the regulatory regimes regarding oil transportation, were found to be insignificant.     

Climate change projections for variables affecting road networks in Europe

Global climate change will affect road networks during this century. The effects will be different in various parts of the world due to differences in local climate change and in the structure and properties of roads. In this paper, climate change projections are presented for climate variables that are most likely to affect the long-term performance of road networks in Europe. We apply four regional climate simulations up to the year 2100 using two plausible future emission scenarios. The results show that the changing climate will require significant adaptation measures in the near future in order to maintain the operability of the European road network.     

A simulation of the simple Mohring model to predict patronage and value of resources consumed for enhanced bus services

Choosing between the competing approaches to providing enhanced bus services requires the ability to predict the effects on patronage and overall benefits to society in terms of Value of Resources Consumed (VRC) of any proposed change. One common approach uses the Mohring model of 1972 and its successors to optimise one or more aspects of the supply of transit services given various level of demand. This paper simulates the operation of a simple circular bus route using the equations of a basic Mohring type model and a Decision Support System (DSS) to endogenise demand under the assumption that there is a fixed demand for travel but commuters can choose between the bus and private vehicle. The selected approach recognises that demand for a particular mode of travel is predicated on the speed of the vehicle in service which is itself determined by the demand for that vehicle (in this model or boarding and alighting time) rather than being determined exogenously. This creates an iterative feedback mechanism whereby changes to the attributes of the bus and car alter mode choice and the speed in service of the bus which, in turn, alters mode choice. The simulation is used to predict changes to patronage and VRC under scenarios regarding changes to the transport network (in terms of fares and running costs, frequency and spacing of bus stops) using parameters from both a Multinomial Logit (MNL) and a Mixed Multinomial Logit (MMNL). The results demonstrate that there are large differences in the size and, in some cases, direction of predicted changes to patronage, VRC and revenue, depending on whether the parameters of the MNL or MMNL model are used.     

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.     

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.     

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.     

通过水下储能系统的蓄电池单元的流:三个接触的似花结构的球状物(英文)

An LES simulation of flow over an accumulator unit of an underwater compressed air energy storage facility was conducted. The accumulator unit consists of three touching underwater balloons arranged in a floral configuration. The structure of the flow was examined via three dimensional iso surfaces of the Q criterion. Vortical cores were observed on the leeward surface of the balloons. The swirling tube flows generated by these vortical cores were depicted through three dimensional path lines. The flow dynamics were visualized via time series snapshots of two dimensional vorticity contours perpendicular to the flow direction; revealing the turbulent swinging motions of the aforementioned shedding-swirling tube flows. The time history of the hydrodynamic loading was presented in terms of lift and drag coefficients. Drag coefficient of each individual balloon in the floral configuration was smaller than that of a single balloon. It was found that the total drag coefficient of the floral unit of three touching balloons, i.e. summation of the drag coefficients of the balloons, is not too much larger than that of a single balloon whereas it provides three times the storage capacity. In addition to its practical significance in designing appropriate foundation and supports, the instantaneous hydrodynamic loading was used to determine the frequency of the turbulent swirling-swinging motions of the shedding vortex tubes; the Strouhal number was found to be larger than that of a single sphere at the same Reynolds number.     

New evidence on walking distances to transit stops: identifying redundancies and gaps using variable service areas

The percentage of the population being served by a transit system in a metropolitan region is a key system performance measure but depends heavily on the definition of service area. Observing existing service areas can help identify transit system gaps and redundancies. In the public transit industry, buffers at 400 m (0.25 miles) around bus stops and 800 m (0.5 miles) around rail stations are commonly used to identify the area from which most transit users will access the system by foot. This study uses detailed OD survey information to generate service areas that define walking catchment areas around transit services in Montreal, Canada. The 85th percentile walking distance to bus transit service is found to be around 524 m for home-based trip origins, 1,259 m for home-based commuter rail trip origins. Yet these values are found to vary based on our analysis using two statistical models. Walking distances vary based on route and trip qualities (such as type of transit service, transfers and wait time), as well as personal, household, and neighbourhood characteristics. Accordingly, service areas around transit stations should vary based on the service offered and attributes of the people and places served. The generated service areas derived from the generalized statistical model are then used to identify gaps and redundancies at the system and route level using Montreal region as an example. This study can be of benefit to transport engineers and planners trying to maximize transit service coverage in a region while avoiding oversupply of service.     

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。