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Your search keyword '"Zeng, Qian"' showing total 151 results
151 results on '"Zeng, Qian"'

47. Association between built environment factors and collective walking behavior in peri-urban area: Evidence from Chengdu.

Author

Zeng, Qian, Wu, Hao, Wei, Yuanyuan, Wang, Jiajing, Zhang, Chengyan, Fei, Ningyuan, and Dewancker, Bart Julien

Subjects
*BUILT environment, *COLLECTIVE behavior, *URBAN planning, *PUBLIC spaces, *SOCIAL interaction
Abstract

Optimizing collective walking has been a pivotal strategy for alleviating the excessive reliance on private cars. As an important criterion for residents' social interaction and mobility vigor, collective walking describes the results of walking activities in streets and positively correlates with the built environments. However, limited attention has been given to the contribution of built environment factors in peri-urban areas towards promoting collective walking. Therefore, this study employed multisource data to assess the impact of these factors on collective walking in peri-urban areas. Our analysis delved into the impact of these factors on collective walking across various urban spaces and explored intervention effects through cross-classification studies that prioritize planning strategies. These results revealed that (1) The impacts of the built environment on collective walking behavior differs in peri-urban areas. (2) Diversity and distance only show significant impacts in peri-urban areas. (3) A distinct spatial mismatch between urban spatial form and collective walking behavior is observed. Subsequent urban design interventions should consider these spatial distribution differences for prioritized zoning planning. Our findings provided convincing evidence that delineated the impact of built environments in peri-urban areas that can guide government and planners to precisely design pedestrian environments through targeted intervention measures. • This study explored the built environment's impact on collective walking behavior. • Different impacts were observed between peri-urban areas and core areas. • This study employed multi-source data to analyze large-scale samples. • Diversity and distance only influence collective walking in peri-urban areas. [ABSTRACT FROM AUTHOR]

Published
2024
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48. Mechanism of self-ignition and flame propagation during high-pressure hydrogen release through a rectangular tube.

Author

Duan, Qiangling, Zeng, Qian, Jin, Kaiqiang, Wang, Qingsong, and Sun, Jinhua

Subjects
*FLAME, *HYDROGEN flames, *SHOCK waves, *HYDROGEN, *TUBES
Abstract

The dynamic mechanisms of self-ignition and flame propagation during high-pressure hydrogen release through a rectangular tube were experimentally investigated using pressure records, flame detection and high-speed photographs. Experimental results show that the minimum burst pressure for self-ignition decreases with an increase in axial distance to the diaphragm and then remains at an almost constant value. The self-ignition onset at the same location of the tube exhibits a certain randomness even if the intensity of the shock wave produced in the tube is similar. Multiple ignitions were observed at the early stage of hydrogen release. They usually had difficulty to sustainably develop and were extinguished owing to oxygen deficiency. At a subsequent stage, the ignition kernel appears again and grows rapidly in the axial and radial directions, finally converging to a complete flame across the tube width. It was found that the radial growth rate of the flame was lower than the axial growth rate. [ABSTRACT FROM AUTHOR]

Published
2022
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50. Effects of CO addition on shock wave propagation, self-ignition, and flame development of high-pressure hydrogen release into air.

Author

Zeng, Qian, Jin, Kaiqiang, Duan, Qiangling, Zhu, Mengyuan, Gong, Liang, Wang, Qingsong, and Sun, Jinhua

Subjects
*SHOCK waves, *THEORY of wave motion, *HYDROGEN flames, *FLAME, *HYDROGEN, *LASER peening
Abstract

In this study, an experimental investigation is conducted to study the effects of CO addition (0%–7.5% vol.) on the self-ignition of pressurized hydrogen leakage. The result shows that more CO addition significantly decreases the likelihood of self-ignition inside the tube and the formation of self-sustained jet flame outside the tube. This can be mostly explained by the reduction of leading shock intensity inside the tube. Furthermore, CO addition effectively inhibits the flame propagation and development inside the tube. For pure hydrogen, the ignited flame quickly develops an intense flame spanning the tube width and eventually form a jet flame in ambient air. However, the H 2 –CO diffusion flame initiated approaching tube sidewall tends to propagate adjacent to the wall or be soon quenched with more CO addition. If the CO-weakened flame spouts to the tube exit, it may not survive the expansion at the tube exit and thus it is quenched. • The shock intensity is reduced in the presence of CO. • The critical pressure for self-ignition increases with CO addition concentration. • Shock intensity variation by CO addition is the main factor affecting self-ignition onset. • Small CO addition can effectively inhibit flame development inside the tube. • H 2 –CO flame spouting from the tube exit tends to be blown out. [ABSTRACT FROM AUTHOR]

Published
2022
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