Parallel sequential turbocharging systems are able to operate in different modes, which are defined according to the turbochargers
that simultaneously boost the engine, and are controlled by means of specific valves. In order to cover the full engine operating
range, a smooth transition between turbocharging operating modes must be ensured. However, important disturbances affect both
boost and exhaust pressure when shifting the operation mode, thus causing non-negligible torque oscillations. This paper presents
different methods for smoothing such undesirable effects during mode transition. Strategies covering optimal synchronization
of the control valves, control of the valves’ position, and correction of the injected fuel during the transition are analysed.
A fully instrumented passenger car engine is used for illustrating the different torque smoothing methods, and experimental
results for transitions during both steady operation and engine accelerations are shown. 相似文献
This paper applies multi-criteria decision-making (MCDM) methods to the evaluation of solutions and alternatives for matching airport system airside (runway) capacity to demand. For such a purpose, ‘building a new runway’ is considered as the solution and candidate airports of the system as alternatives for implementing the solution. The alternative airports are characterized by their physical/spatial, operational, economic, environmental, and social performance represented by corresponding indicator systems which, after being defined and estimated under given operating scenarios, are used as evaluation attributes/criteria by the selected MCDM methods. Two MCDM methods – Simple Additive Weighting and Technique for Order of Preference by Similarity to Ideal Solution – are applied to the case of the London airport system to rank and select the preferred alternative from three candidate airports – Heathrow, Gatwick, and Stansted – for where a new runway could be built. 相似文献
Few studies have examined the relationship between micro-scale features of the built environment and street segment usage. Micro-scale features of the built environment include the width of the sidewalk, the presence of amenities such as benches and trash bins, and the presence of crossing aids such as stoplights and crosswalks. This study employs segment-level primary data collected for 338 street segments in close proximity to one of 71 bus rapid transit stations in Bogotá, Colombia. We also use secondary data to control for area-level characteristics such as density, socio-economic stratum, unemployment, and crime. Factor and regression analyses are to use identify two dimensions of the built environment that are associated with higher levels of pedestrian activity: pedestrian-friendly amenities, comprised of wider and higher quality sidewalks and the presence of amenities such as benches, garbage cans, and bike paths; and connectivity, comprised of higher levels of road density, three- and four-way intersections, and density. In addition, we find greater pedestrian activity on segments with higher development intensity, with more mix of land uses, and with more crossing aids. Although the relationships identified are not causal, they are suggestive in terms of planning successful built environment interventions. 相似文献
Transportation - Spatiotemporal data, and more specifically origin–destination matrices, are critical inputs to mobility studies for transportation planning and urban management purposes.... 相似文献
In order to predict the monthly usage frequency of members of a car-sharing scheme by analysing the gradual change of behaviour over time, a new model is proposed based on the Markov Chains model with latent stages. The model accounts for changing patterns of frequency from soon after signing up to later stages by including five latent user ‘life stages’. In applying the model to panel data from Montreal’s free-floating carsharing service the authors calculate each user’s ’lifetime’ applied to ‘system operation time’, the time period since the start of the scheme. Three-fold validation reveals effective performance of the model for both lifetime and system operation time dimensions. The model is further applied to illustrate how previous carsharing experience and the extension of the scheme to a larger area can affect usage frequency changes. We conclude that this approach is effective for usage prediction for novel transport schemes.
Transportation - Evolutionary algorithms have been used extensively over the past 2 decades to provide solutions to the Transit Network Design Problem and the Transit Network and Frequencies... 相似文献
Transportation - This paper introduces a method for estimating the interregional transportation of certain commodities in those cases where the commodity flows are not readily available and only... 相似文献
Smart card fare collection systems are widely used nowadays in urban public transport networks. These systems are bound to facilitate the collection and management of revenues in transit authorities. However, since smart card systems collect a large amount of data on a daily basis, they can be exploited to better characterize the demand and supply of public transport in subways, tramways and bus networks, while data at an individual level should remain strictly confidential. The spatial and temporal dimensions of the data make it very interesting for planning purposes, but the data must first be validated and completed before further analysis. This article presents the results of five years of research conducted in collaboration with theSociété de transport de l??Outaouais, in Quebec. The following analyses are presented: error processing, estimation of alighting points, diffusion of operational statistics, analysis of user behaviour, analysis of network performance, comparison with household survey data and user loyalty modelling. 相似文献
ABSTRACT It is essential that the pedestrian environment accommodates all users so they can participate in everything the community has to offer. However, people with disabilities (PWDs) often find it difficult to navigate this environment because of physical and social accessibility factors. While we know a great deal about which factors act as barriers and facilitators to mobility, we do not know enough about how they influence navigation (i.e. planning a route, en route decisions, and route learning) or how they can be improved. A scoping review was conducted to identify these factors, assess their implications, and suggest future directions. In total, 3394 studies were found and screened, 163 full-text articles were reviewed, and 37 articles met the inclusion criteria for the final review. These studies focused on those with visual impairments, navigating crosswalks, and the cognitive elements of navigation. Future research is needed that includes more types of disabilities, considers the navigational process from planning to arrival, and evaluates interventions. 相似文献