Influence of translational vehicle dynamics on heavy vehicle noise emission

The co-benefits of electric mobility in reducing traffic noise and chemical air pollution: Insights from a transit-oriented city

Traffic noise is a growing threat to the urban population. Prolonged exposure to traffic noise has been linked to negative health consequences such as annoyance, sleep disturbances and cardiovascular diseases. While electric vehicles are known to have lower noise profiles, the impacts of electric mobility on traffic noise, especially for electrified heavy-duty vehicles, have not been thoroughly examined. This study aims to examine the impacts of both electric light-duty vehicles and electric buses on traffic noise levels in a highly urbanized city. Traffic noise along the source line and pedestrian network was first estimated and mapped to illustrate its spatiotemporal variations. Then, scenario analysis was used to compare the impacts. Population potentially benefiting from reduced traffic noise in the neighbourhoods and the associated health impacts were also estimated. Results indicate that electric buses have a greater potential to reduce traffic noise, with a maximum reduction of 4.4 dBA during daytime in the urban cores. With all bus fleet electrified, around 60% of the population can benefit from a reduction of 1 dBA at the street environment, 15.3% for 1-2 dBA, and 4.3% for more than 2 dBA. The estimated reduction of preventable deaths and preventable cases of diseases per 100,000 population are 4.15 and 112.99 respectively. The findings shed important insights into prioritizing bus routes to be electrified in urban areas for maximizing health co-benefits.

Noise Emission Models of Electric Vehicles Considering Speed, Acceleration, and Motion State

Electric vehicles, known for their low-noise emission, are popular and widespread in metropolises in China, and they provide an opportunity for a reduction in environmental noise from vehicles. To understand the noise from electric vehicles better, this study develops noise emission models considering speed, acceleration, and motion state. The model construction is based on the data collected from a pass-by noise measurement experiment in Guangzhou, China. The models describe a linear relationship between the noise level, the logarithm of speed, and the acceleration for multiple motion states (i.e., the constant-speed state, the acceleration state, and the deceleration state). From the spectrum analysis, the low-frequency noise is barely affected by the speed and acceleration, but the noise at a certain frequency is most sensitive to them. Compared to other models, the proposed ones have the highest accuracy and the greatest ability for extrapolation and generalization.

Modification of Cold-Sprayed Cu-Al-Ni-Al2O3 Composite Coatings by Friction Stir Technique to Enhance Wear Resistance Performance

An innovative hybrid process combining two effective surface modification techniques, cold spray (CS) and friction stir processing (FSP), was proposed to refine the microstructure of Cu-Al-Ni-Al2O3 composite coating material. FSP was performed under constant rpm using extensive cooling conditions to remove heat generated during the operation. Microstructural characterizations such as optical micrography (OM), scanning electron microscopy (SEM), Electron Backscatter Diffraction (EBSD), Energy-dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD) were performed to evaluate the microstructural evolution of the coatings before and after FSP treatment. Mechanical characterizations such as microhardness and elastic modulus were measured using micro-depth sensing techniques. Furthermore, sliding wear tests were performed to study the wear resistance of the as-sprayed and processed coatings. The findings suggest that after FSP, there is an improvement in microstructure of the coating layers with the elimination of particle boundaries, micro-pores and micro-cracks, and processed coatings showed an improvement in mechanical properties. Furthermore, there was a slight reduction in the wear rate of the deposited CuAlNi-Al2O3 composite coatings. Among all the test coatings, friction stir processed S1 coating showed the lowest wear rate, which was an almost two times lower wear rate than its unprocessed counterparts.

Road transportation green productivity and its threshold effects from environmental regulation

This paper uses the global Malmquist-Luenberger index to investigate changes in road transportation green productivity from 2010 to 2017, incorporating undesirable outputs into the analytical framework. Furthermore, the relationship between environmental regulation and green productivity is tested by the panel threshold model. At the area level, the improvement of green productivity in western China benefits from a catch-up effect and improved scale efficiency. Moreover, the driving factor improving green productivity in China's central and eastern areas is mainly the scale economy, and technology regress is the hindering factor. Research and development investment and government fiscal expenditure both show a single-threshold effect on green productivity. That is, their values in relation to thresholds cause differences in the impact of environmental regulation on green productivity. Our analysis shows that economic development can significantly promote green productivity, while highway density can significantly hinder it. Based on the evidence presented, we put forward practical suggestions for improving green productivity.

Characteristics analysis of near-field and far-field aerodynamic noise around high-speed railway bridge

The aerodynamic noise around the high-speed railway bridge is studied by the train-bridge-flow field numerical model and theory analysis. With the background of the Beijing-Shanghai high-speed railway line in China, based on the broadband noise sources method and acoustic analogy theory, both the intensity characteristics of near-field aerodynamic noise sources of the train and the spatial distribution characteristics of far-field aerodynamic noise around the bridge are analyzed. The results show that there is the largest sound source energy on the nose tip of the high-speed train; the fluctuating pressure between air and train surface contributes the most to aerodynamic noise; along the longitudinal direction of the bridge, the aerodynamic noise energy near the junction of train tail and body is the strongest; along the transverse direction of the bridge, the aerodynamic noise energy decreases gradually with the distance from the centerline of the railway; along the vertical direction, the aerodynamic noise energy is the strongest at a location of 1.2 m above the top surface of the rail; the train speed, train type, and the height variation of the bridge pier can affect the distribution of far-field aerodynamic noise.

Measuring performance of road transportation industry in China in terms of integrated environmental efficiency in view of Streaming Data

Road transportation industry not only promotes economic development, but also brings many environmental issues in China. It is necessary to evaluate the integrated environmental efficiency of road transportation industry, including carbon dioxide emissions, traffic accident and traffic noise which is a Steaming Data. In this study, a parallel DEA model with sub-system preference is proposed to measuring the integrated environmental efficiency of road transportation industry in 2013-2017 considering various undesirable outputs. Then, the convergence analysis approach is employed to investigate the regional differences in terms of efficiency of road transportation. The empirical results show that the overall integrated environmental efficiency underperformed nationwide, and the passenger transportation sub-system outperformed freight transportation when the latter is restricted in some hours. From a regional perspective, the efficiency performances show downward trends in areas eastern, central and western. The passenger transportation sub-system outperforms in eastern area and the freight transportation outperforms in central area. Furthermore, the convergence analysis results indicate that the integrated environmental efficiency in eastern and western areas not only converged to their own stable levels but also that the differences in the integrated environmental efficiency between eastern and western areas are condensing. The contributions of this study lie in not only proposing a parallel DEA model with sub-system preference and considering the streaming data, but also providing suggestions to improving the road transportation industry in terms of integrated environmental efficiency. Finally, the research limitations and further research directions were conducted.