Time filter

Source Type

Yan X.,Wuhan University of Technology | Ma M.,Wuhan University of Technology | Ma M.,Transport planning and research institute | Huang H.,Central South University | And 2 more authors.
Accident Analysis and Prevention | Year: 2011

This research presents a comprehensive analysis of motor vehicle-bicycle crashes using 4 years of reported crash data (2004-2007) in Beijing. The interrelationship of irregular maneuvers, crash patterns and bicyclist injury severity are investigated by controlling for a variety of risk factors related to bicyclist demographics, roadway geometric design, road environment, etc. Results show that different irregular maneuvers are correlated with a number of risk factors at different roadway locations such as the bicyclist age and gender, weather and traffic condition. Furthermore, angle collisions are the leading pattern of motor vehicle-bicycle crashes, and different irregular maneuvers may lead to some specific crash patterns such as head-on or rear-end crashes. Orthokinetic scrape is more likely to result in running over bicyclists, which may lead to more severe injury. Moreover, bicyclist injury severity level could be elevated by specific crash patterns and risk factors including head-on and angle collisions, occurrence of running over bicyclists, night without streetlight, roads without median/division, higher speed limit, heavy vehicle involvement and older bicyclists. This study suggests installation of median, division between roadway and bikeway, and improvement of illumination on road segments. Reduced speed limit is also recommended at roadway locations with high bicycle traffic volume. Furthermore, it may be necessary to develop safety campaigns aimed at male, teenage and older bicyclists. © 2011 Elsevier Ltd. All rights reserved. Source

Wang C.,Beijing Normal University | Zhang L.,Beijing Normal University | Liu J.,Transport planning and research institute
Frontiers of Earth Science | Year: 2013

Assessing the extent to which all bio-fuels that are claimed to be renewable are in fact renewable is essential because producing such renewable fuels itself requires some amount of non-renewable energy (NE) and materials. Using hybrid life cycle analysis (LCA)-from raw material collection to delivery of pellets to end users-the energy cost of wood pellet production in China was estimated at 1. 35 J/J, of which only 0. 09 J was derived from NE, indicating that only 0. 09 J of NE is required to deliver 1 J of renewable energy into society and showing that the process is truly renewable. Most of the NE was consumed during the conversion process (46. 21%) and delivery of pellets to end users (40. 69%), during which electricity and diesel are the two major forms of NE used, respectively. Sensitivity analysis showed that the distance over which the pellets are transported affects the cost of NE significantly. Therefore the location of the terminal market and the site where wood resources are available are crucial to saving diesel. © 2013 Higher Education Press and Springer-Verlag Berlin Heidelberg. Source

He J.-C.,Transport planning and research institute
Huanjing Kexue/Environmental Science | Year: 2012

Although aircrafts are of great importance in transportation in China, there has been rare study on air pollutant emissions of aircrafts until now. Based on the annually statistical data collected by the Statistic Center of Civil Aviation of China, using the emission factor method derived from fuel consumption, the air pollutant emissions of aircrafts during 1980-2009 were calculated, and their emission intensities and dynamic characteristics were analyzed. The results show that the emissions of SO2, CO, NOx and HC from aircrafts of China Civil Aviation increased from 0.31 thousand, 1.89 thousand, 2.25 thousand and 3.14 thousand tons in 1980 to 11.83 thousand, 72.98 thousand, 87.05 thousand and 121.59 thousand tons in 2009, indicating a increase of 0.397 thousand, 2.45 thousand, 2.92 thousand and 4.08 thousand tons per year, respectively. The emission intensities of SO2, CO, NOx and HC decreased significantly from 0.624, 3.806, 4.53 and 6.322 g·(t·km)-1 in 1980 to 0.275, 1.697, 2.025 and 2.828 g·(t·km)-1 in 2009, respectively. SO2, CO, NOx emissions of aircrafts of China Civil Aviation accounted very little of each total emissions in China, and the air pollutant emissions from aircrafts of China Civil Aviation was less than those from other industries in China. Source

Yang Z.,Transport planning and research institute | Zhao Y.,Peking University
Wireless Personal Communications | Year: 2016

We propose an adaptive resource allocation algorithm for scalable H.264 video transmission over orthogonal frequency-division multiple-access (OFDMA) systems. The algorithm explores the scalability of the video codec and the multiuser diversity of OFDMA systems to achieve enhanced efficiency and video quality. We use the peak signal-to-noise ratio (PSNR) as the measure metric of video quality, and jointly optimize the video layer extraction and radio resource allocation, considering the heterogeneity of video sources and channel conditions. Given the fact that different quality layers of the video have different importance, an adaptive modulation and coding scheme is proposed where a fixed coding rate is used for each quality layer, and unequal error protection is implemented for different layers. We also propose a subcarrier allocation algorithm to assign subcarriers for different layers of different users’ videos to maximize the average PSNR of users while satisfying the base layer requirement. The proposed resource allocation algorithm has a low complexity and is suitable for practical implementations. We further develop an end-to-end simulation testbed to demonstrate the effectiveness of the proposed transmission scheme. © 2016 Springer Science+Business Media New York Source

Zhou L.,Transport planning and research institute
Advanced Materials Research | Year: 2014

Different hydrated lime content in asphalt mastic greatly influences the performances of asphalt mixture. The aim of this paper is to study asphalt mastic made with different content of hydrated lime was used in Dynamic Shear Rheological and Viscosity Tests. The optimum hydrated lime content was proposed in terms of test results above. The results illustrated that hydrated lime was an appropriate addition agent which can improve asphalt mastic properties greatly, however, too much hydrated lime may result in the decrease of asphalt mixture performances. © (2014) Trans Tech Publications, Switzerland. Source

Discover hidden collaborations