Tourism networks are an important research part of tourism geography. Despite the significance of transportation in shaping tourism networks, current studies have mainly focused on the “daily behavior” of urban travel at the expense of tourism travel, which has been regarded as an “exceptional behavior”. To fill this gap, this study proposes a framework for exploring the spatial and temporal characteristics of urban tourism travel by taxi. We chose Shenzhen, a densely populated mega-city in China with abundant tourism resources, as a case study. First, we extracted tourist trips from taxi trajectories and used kernel density estimation to analyze the spatial aggregation characteristics of tourist trip origins. Second, we investigated the spatial dependence of tourist trips using local spatial autocorrelation analysis (Getis-Ord Gi*). Third, we explored the correlations between the tourist trip origins and urban geographic contextual factors (e.g., catering services and transportation facilities) using a geographically weighted regression model. The results show the following: (1) the trends between the coverage of tourist travel networks and the volume of tourist trips are similar; (2) the spatial interaction intensity of urban tourism has grouping and hierarchical characteristics; and (3) the spatial distribution of tourist trips by taxi is uneven and influenced by the distribution of urban morphology, tourism resources, and the preferences of taxi pick-up passengers. Our proposed framework and revealed spatial and temporal patterns have implications for urban tourism traffic planning, tourism product development, and tourist flow control in tourist attractions.

To solve the misfire problem of lithium-ion batteries in storage and transportation, a method of using cryogenic control to prevent thermal runaway of lithium-ion batteries is proposed, and a serial of tests of thermal runaway of ternary lithium-ion batteries under the effect of cryogenic cooling are carried out. The results show that cryogenic cooling can weaken the energy release of a lithium-ion battery after thermal runaway by reducing its internal reaction activity and then blocking the chain propagation of thermal runaway between battery packs. The lower the temperature of a lithium-ion battery, the more difficult it is for the battery to develop thermal runaway; when the temperature drops to −20 °C, thermal runaway propagation does not occur. The highest CO concentration and mass loss in the test chamber were reduced by 83.1% and 75.9%, respectively, compared with the normal temperature group. When the temperature dropped below −30 °C, the battery that was directly punctured did not develop thermal runaway. This discovery can be used in the transportation and storage of lithium batteries.

In this study, an underground pipe gallery was taken as the research subject to explore the influence of nitrogen injection flow rate and pipe diameter on the fire extinguishing efficiency in an underground narrow confined space. A liquid nitrogen fire extinguishing test system for the underground narrow confined space was built. The fire extinguishing time, flame height, temperature, and oxygen concentration under different conditions were recorded by liquid nitrogen fire extinguishing tests, and the variations in the characteristics of these data were analyzed. Furthermore, the fire suppression factor, cooling factor, and asphyxiation factor were introduced to quantify the influence of the nitrogen flow rate and pipe diameter on extinguishing efficiency. According to the results, the fire was effectively extinguished by liquid nitrogen in the underground confined space through asphyxiation as the main fire extinguishing mechanism, and the extinguishing time was about 95.5% less than that in the self-extinguishing test. Although the fire suppression efficiency is positively related to the nitrogen injection flow, the asphyxiation efficiency can be reduced when the flow rate is excessive or too weak. Additionally, the asphyxiation factor and fire suppression factor are highly sensitive to the injection pipe diameter. Therefore, a valuable reference is provided in this study for promoting the future engineering application of liquid nitrogen fire extinguishment.