Search

The fuel consumption and greenhouse gas (GHG) emission patterns of taxis are in accordance with the urban structure and daily travel footprints of residents. With taxi trajectory data from the intelligent transportation system in Xi'an, China, this study excludes trajectories from electric taxis to accurately estimate GHG emissions of taxis. A gradient boosting decision tree (GBDT) model is employed to examine the nonlinear influence of the built environment (BE) on the GHG emissions of taxis on weekdays and weekends in various urban areas. The research findings indicate that the GHG emissions of taxis within the research area exhibit peak levels during the time intervals of 7:00–9:00, 12:00–14:00, and 23:00–0:00, with notably higher emission factors on weekends than on weekdays. Moreover, a clear nonlinear association exists between BE elements and GHG emissions, with a distinct impact threshold. In the different urban areas, the factors that influence emissions exhibit spatial and temporal heterogeneity. Metro/bus/taxi stops density, residential density, and road network density are the most influential BE elements impacting GHG emissions. Road network density has both positive and negative influences on the GHG emissions in various urban areas. Increasing the road network density in subcentral urban areas and increasing the mixed degree of urban functions in newly developed urban centers to 1.85 or higher can help reduce GHG emissions. These findings provide valuable insights for reducing emissions in urban transportation and promoting sustainable urban development by adjusting urban functional areas. [ABSTRACT FROM AUTHOR]

Existing studies have limited evidence about the complex nonlinear impact mechanism of road network topology and built environment on bike-sharing systems' greenhouse gas (GHG) emission reduction benefits. To fill this gap, we examine the nonlinear effects of road network topological attributes and built environment elements on the potential GHG emission reduction of dockless bike-sharing (DBS) trips in Shenzhen, China. Various methods are employed in the research framework of this study, including a GHG emission reduction estimation model, spatial design network analysis (sDNA), gradient boosting decision tree (GBDT), and partial dependence plots (PDPs). Results show that road network topological variables have the leading role in determining the potential GHG emission reduction of DBS trips, followed by land use variables and transit-related variables. Moreover, the nonlinear impacts of road network topological variables and built environment variables show certain threshold intervals for the potential GHG emission reduction of DBS trips. Furthermore, the impact of built environment on the potential GHG emission reduction of DBS trips is moderated by road network topological indicators (closeness and betweenness). Compared with betweenness, closeness has a greater moderating effect on built environment variables. These findings provide empirical evidence for guiding bike-sharing system planning, bike-sharing rebalancing strategy optimization, and low-carbon travel policy formulation. [ABSTRACT FROM AUTHOR]

Catalytic ozonation is a promising method for simultaneous removal of NO x and Cl-VOCs, but needs to clarify their interaction mechanism and the influence of catalyst acidity. In this paper, the simultaneous catalytic ozonation of NO and dichloromethane (DCM) on Mn/H-ZSM-5 molecular sieve catalysts were investigated experimentally. Results show that the overall acidity, acid sites type and intensity have a significant impact on the degradation efficiency, the conversion path of Cl element, and the interaction of NO/DCM adsorption-degradation. Nevertheless, regardless of catalysts, NO could be preferentially oxidized by ozone to generate NO 2 in co-ozonation process, which inhibited and even shielded DCM ozonation at O 3 /DCM ratio <1.7. In addition, the highly active oxidizing species such as NO 3 /N 2 O 5 , produced by the deep ozonation of NO 2 , exhibited a synergistic effect on the conversion of DCM and intermediates, which in turn weakened NO 2 deep oxidation. Specifically, NO addition caused a general decrease in the HCl selectivity, and a slight increase in the CHCl 3 selectivity of all samples, while the Cl 2 selectivity was determined by the overall catalyst acidity. The samples with higher overall acidity exhibited lower activity for DCM degradation. In particular, for samples with the weak overall acidity but strong acid sites, the sum selectivity of HCl, Cl 2 , and CHCl 3 was significantly improved under the interplay effect of NO, indicating that strong acidic sites were beneficial to the complete degradation of DCM. In-situ DRIFTS revealed that aldehydes and carboxylates were the key intermediates of DCM ozonation. In the co-ozonation, NO and its oxidation products (such as nitrates) could promote the formation and conversion of these intermediates, and further converted into CO and CO 2 by the active oxidant from ozone. Finally, the interference of H 2 O and SO 2 on the NO/DCM co-ozonation were revealed. [ABSTRACT FROM AUTHOR]

The poor electronic conductivity and low intrinsic electrocatalytic activity of metal organic frameworks (MOFs) greatly limit their direct application in electrocatalytic reactions. Herein, we report a conductive two-dimensional Ď€ â€" d conjugated Ni and Co bimetal organic framework (MOF)â€"NiCo-(2,3,6,7,10,11-hexaiminotriphenylene) (NiCo-HITP) nanorods decorated with highly dispersed Co3O4 nanoparticles (NPs) as a promising bi-functional electrocatalyst towards oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) through an effective and facile strategy by modifying the rod-shaped -Ni3HITP2 crystals using cobalt ions. The triggered electrocatalytic activity of the resulting MOF-based materials was achieved by increasing the electrical conductivity (7.23 S cmâˆ'1) originated from Ni3HITP2 substrate and also by creating the cooperative catalysis sites of Coâ€"N x and Co3O4 NPs. Optimized syntheses show a promising ORR activity with a high half-wave potential (0.77 V) and also a significantly improved OER activity compared with pure Ni3HITP2 in alkaline electrolyte. Furthermore, a rechargeable Znâ€"air battery using the as-prepared material as air-cathode also shows a high power density (143.1 mW cmâˆ'2)â€"even comparable to a commercial Pt/C-RuO2-based battery. This methodology offers a new prospect in the design and synthesis of non-carbonized MOF bi-functional electrocatalysts for efficient catalysis towards ORR and OER. [ABSTRACT FROM AUTHOR]

In the present paper, the dynamic behavior of cavitation bubbles near a wall is experimentally investigated with a focus on the retardant effects of the wall on the collapsing dynamics of the bubble. In the present experiments, a cavitation bubble is generated by a focused laser beam with its behavior recorded through high-speed photography. During the data analysis, the influences of non-dimensional bubble–wall distance on the bubble collapsing dynamics are qualitatively and quantitatively investigated in terms of the interface evolution, the velocities of the poles, and the movement of the bubble centroid. Our results reveal that the presence of the wall could significantly affect the collapsing characteristics, leading to a dramatic difference between the moving velocities of interfaces near and away from the wall. With the decrease of the bubble–wall distance, the effects will be gradually strengthened with a rapid movement of the bubble centroid during the final collapse. Finally, a physical interpretation of the phenomenon is given based on the bubble theory, together with a rough estimation of the induced water hammer pressure by the bubble collapse. [ABSTRACT FROM AUTHOR]

The poor electronic conductivity and low intrinsic electrocatalytic activity of metal organic frameworks (MOFs) greatly limit their direct application in electrocatalytic reactions. Herein, we report a conductive two-dimensional π - d conjugated Ni and Co bimetal organic framework (MOF)-NiCo-(2,3,6,7,10,11-hexaiminotriphenylene) (NiCo-HITP) nanorods decorated with highly dispersed Co 3 O 4 nanoparticles (NPs) as a promising bi-functional electrocatalyst towards oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) through an effective and facile strategy by modifying the rod-shaped -Ni 3 HITP 2 crystals using cobalt ions. The triggered electrocatalytic activity of the resulting MOF-based materials was achieved by increasing the electrical conductivity (7.23 S cm -1 ) originated from Ni 3 HITP 2 substrate and also by creating the cooperative catalysis sites of Co-N x and Co 3 O 4 NPs. Optimized syntheses show a promising ORR activity with a high half-wave potential (0.77 V) and also a significantly improved OER activity compared with pure Ni 3 HITP 2 in alkaline electrolyte. Furthermore, a rechargeable Zn-air battery using the as-prepared material as air-cathode also shows a high power density (143.1 mW cm -2 )-even comparable to a commercial Pt/C-RuO 2 -based battery. This methodology offers a new prospect in the design and synthesis of non-carbonized MOF bi-functional electrocatalysts for efficient catalysis towards ORR and OER., (© 2022 IOP Publishing Ltd.)