印度应对城市机动化策略

为应对快速的城市机动化进程及其带来的负面影响,印度政府早期采取诸如修建立交桥和拓宽道路等办法,结果却导致了更多的机动车数量增加和更严重的交通拥堵。为此,印度政府实施了＂国家城市交通政策＂,重点投资公共交通和非机动交通方式;同时还制定了＂国家城市更新计划＂,以此建立鼓励地方政府执行国家政策的激励机制,提高对城市基础设施的投资水平。这些创新政策的实施,推动了一系列公共交通项目的发展,也促进了城市内部交通体制改革和城市综合交通发展规划的制定。     

Non-linear aerothermoelastic modeling and behavior of a double-wedge lifting surface

The design of the re-entry space vehicles and high-speed aircraft structures requires special attention to the non-linear thermoelastic and aerodynamic instabilities. The thermal effects are important since temperature environment influences significantly the static and dynamic behaviors of flight structures in supersonic/hypersonic regimes. The dynamic behavior of a double-wedge lifting surface with combined freeplay and cubic stiffening structural nonlinearities in both plunging and pitching degrees-of-freedom (DOF) operating in supersonic/hypersonic flight speed regimes has been analyzed. In addition a third order piston theory aerodynamics (PTA) is used to evaluate the non-linear unsteady aerodynamic loads applied to the wing section. Loss of torsional stiffness that may be incurred by lifting surfaces subjected to axial stresses induced by aerodynamic heating is also considered. The aerodynamic heating effect is estimated based on the adiabatic wall temperature due to high speed airstreams. It is demonstrated that serious losses of torsional stiffness may occur in such lifting surfaces; the influence of various parameters such as flight condition, thickness ratio, freeplays and pitching stiffness nonlinearity are discussed.     

Effect of fuel injection strategies on the combustion process in a PFI boosted SI engine

A low-cost solution based on fuel injection strategies was investigated to optimize the combustion process in a boosted port fuel injection spark ignition (PFI SI) engine. The goal was to reduce the fuel consumption and pollutant emissions while maintaining performance. The effect of fuel injection was analyzed for the closed and open valve conditions, and the multiple injection strategies (MIS) based on double and triple fuel injection in the open-valve condition. The tests were performed on an optical accessible single-cylinder PFI SI engine equipped with an external boost device. The engine was operated at full load and with a stoichiometric ratio equivalent to that of commercial gasolines. Optical techniques based on 2D-digital imaging were used to follow the flame propagation from the flame kernel to late combustion phase. In particular, the diffusion-controlled flames near the valves and cylinder walls, due to fuel deposition, were studied. In these conditions, the presence of soot was measured by two-color pyrometry, and correlated with engine parameters and exhaust emissions measured by conventional methods. The open valve fuel injection strategies demonstrated better combustion process efficiency than the closed ones. They provided very low soot levels in the combustion chamber and engine exhaust, and a reduction in specific fuel consumption. The multiple injection strategies proved to be the best solution in terms of performance, soot concentration, and fuel consumption.     

Empirical approach for predicting the cetane number of biodiesel

The cetane number is an indicator of ignition quality and thus of fuel quality in the realm of diesel engines. It is conceptually similar to the octane number used for gasoline. Generally, a compound that has a high octane number tends to have a low cetane number and vice versa. The cetane number of a diesel fuel is related to the ignition delay time. In our work the first approach is a statistical one the accuracy of which depends upon the data obtained from various papers and literature sources, as all equations used were based on this data. During prediction using more than one equation is a good approach, as it provides the accuracy as well as the relative error. The second approach is also a statistical one, but its value depends upon the saponification number and iodine value. Therefore the accuracy of this equation may be higher, since we can collect the data for saponification numbers and iodine values from literature, without needing to calculate them. Using the saponification number and iodine value we can select an optimal biodiesel as generally a good biodiesel is selected using these three values. Thus the second approach allows us the freedom to select a biodiesel.     

Integrated imputation of activity-travel diaries incorporating the measurement of uncertainty

Procedures to transform GPS tracks into activity-travel diaries have been increasingly addressed due to their potential benefit to replace traditional methods used in travel surveys. Existing approaches for data annotation however are not sufficiently accurate, which normally involves a prompted recall survey for data validation. Imputation algorithms for transportation mode detection seem to be largely dependent on speed-related features, which may blur the quality of classification results, especially with transportation modes having similar speeds. Therefore, in this paper we propose an enhanced integrated imputation approach by incorporating the critical indicators related to trip patterns, reflecting the effects of uncertain travel environments, including bus stops and speed percentiles. A two-step procedure which embeds a segmentation model and a transportation mode inference model is designed and examined based on purified prompted recall data collected in a large-scale travel survey. Results show the superior performance of the proposed approach, where the overall accuracy at trip level reaches 93.2% and 88.1% for training and surveyed data, respectively.     

Computational Vibration Analysis of Vehicle Shimmy by a Power-Work Method

This paper presents the simulation of vehicle shimmy for a mid-size truck with focus on a computational analysis tool that measures the power and corresponding work in dissipating the excitation energy. After a review of shimmy theory the power and work equations and their response classification in vibrating systems are introduced. Next, model validation compares the full vehicle model to an actual test vehicle. Finally, two designs that suppress shimmy in the test vehicle are analyzed in the model by the power-work method, showing components that effectively dissipate the shimmy energy.     

Independent control of all-wheel-drive torque distribution

The sophistication of all-wheel-drive (AWD) technology is approaching the point where the drive torque to each wheel can be independently controlled. This potentially offers vehicle handling enhancements similar to those provided by dynamic stability control, but without the inevitable reduction in vehicle acceleration. Independent control of AWD torque distribution would therefore be especially beneficial under acceleration close to the limit of stability. A vehicle model of a typical sports sedan was developed in Simulink, with fully independent control of torque distribution. Box-Behnken experimental design was employed to determine which torque distribution parameters have the greatest impact on the vehicle course and acceleration. A proportional-integral control strategy was implemented, applying yaw rate feedback to vary the front-rear torque distribution and lateral acceleration feedback to adjust the left-right distribution. The resulting system shows a significant improvement over conventional driveline configurations under aggressive cornering acceleration on a high-μ surface. The performance approaches the theoretical limit for these conditions. In the medium term, such a system is only likely to be economically viable for premium vehicles. However, a future revolution of powertrain technology towards, for example, wheel-mounted motors, could realize these handling benefits far more widely.     

Application of Optimal Control Theory to Inverse Simulation of Car Handling

The application of Optimal Control Theory to time-optimal inverse simulation of car handling was investigated. Time-optimal inverse simulation of car handling involves the calculation of driver actions required to perform specified manoeuvres, in as short a time as possible. Driver actions consist of time-histories of front wheel steer rate and longitudinal force. Optimal time-histories of these quantities were calculated using the Gradient method after formulating the problem as one of optimal control. Simulation results are presented for two different cars performing similar lane-changes. These results show significant differences in necessary driver actions for different cars and demonstrate the suitability of the approach taken.     

Influence of the residential and work environment on car use in dual-earner households

This paper analyses whether the decision to commute by car is influenced by built environment characteristics of residential neighbourhoods and, more especially, of work locations, taking into account interdependencies between household partners. It shows that the residential environment only affects car use among single-earners. Conversely, for all commuters, but in particular for dual-earners, characteristics of the work location affect whether they commute by car. Even in dual-earner households with two cars, work environment plays a role. We found that in cases of dual-earners with only one car, the partners with the longest commuting distances and the lowest density work locations are most likely to commute by car. Moreover, in households with young children, men are more inclined to leave the car at home. Other features relating to work also affect car commuting, including work flexibility and, especially, possession of a company car. We conclude that future policies aimed at reducing car use should place greater focus on work factors.     

Real-time Monitoring of Subsea Gas Pipelines,Offshore Platforms,and Ship Inspection Scores Using an Automatic Identification System

The aim of this research is to develop an algorithm and application that can perform real-time monitoring of the safety operation of offshore platforms and subsea gas pipelines as well as determine the need for ship inspection using data obtained from automatic identification system (AIS). The research also focuses on the integration of shipping database, AIS data, and others to develop a prototype for designing a real-time monitoring system of offshore platforms and pipelines. A simple concept is used in the development of this prototype, which is achieved by using an overlaying map that outlines the coordinates of the offshore platform and subsea gas pipeline with the ship’s coordinates (longitude/latitude) as detected by AIS. Using such information, we can then build an early warning system (EWS) relayed through short message service (SMS), email, or other means when the ship enters the restricted and exclusion zone of platforms and pipelines. The ship inspection system is developed by combining several attributes. Then, decision analysis software is employed to prioritize the vessel’s four attributes, including ship age, ship type, classification, and flag state. Results show that the EWS can increase the safety level of offshore platforms and pipelines, as well as the efficient use of patrol boats in monitoring the safety of the facilities. Meanwhile, ship inspection enables the port to prioritize the ship to be inspected in accordance with the priority ranking inspection score.