Two types of bituminous coal were extracted with tetrahydrofuran solvent using microwave-assisted method at 50°C and atmospheric pressure. Pore structure parameters and wettability of raw coals and their residues were separately tested with nitrogen adsorption and capillary penetration method. Fourier transform infrared spectrometer was employed for analysis of surface functional groups of raw coals and their residues. Results showed remarkably degraded wettability of coal, especially gas coal, after extraction, whereas wetting height of raw coal reached more than twice that of residual coal within the same wetting time. Given the different storage characteristics of organic micromolecules in coal, pore volume of coal increased after extraction, and solvent extraction exerted different effects on pores. Pores of gas coal expanded with reduced specific surface area and improvement in hydrophobicity. Pores of coking coal increased with increasing specific surface area and degrading hydrophobicity. Organic micromolecules in coal and several side-chain groups in macromolecular skeleton structure were dissolved, reducing contents of functional groups in coal, decreasing quantities of groups, such as methyl and carbonyl, on coal surface, and modifying microcosmic surface characteristics of coal and improving hydrophobicity. Through comprehensive analysis, pore structure, and microcosmic surface characteristics of coal jointly determined its wettability.

As a highly effective and environmentally benign suppression agent, liquid nitrogen (LN₂) has been widely used for fire extinguishing in plants, dwellings, enclosed underground tunnels, and other confined spaces through cooling and inerting. It is of great significance to understand the cooling and inerting effects of LN₂ injected into a confined space. A confined-space experimental platform was developed to study the injecting LN₂ into the platform with different injection parameters, such as mass flux, pipe diameter, and inclination angle. In addition, a mathematical model of quantitatively assessing cooling and inerting effects was proposed by using heat transfer capacity, inerting coefficient, and cooling rate. Results showed that the inerting effect was gradually enhanced with a mass flux increasing from 0.014 to 0.026 kg/s and then tended to level off; an appropriate pipe diameter of 12 mm was optimal for the cooling and inerting effects in this experiment. In addition, a positively increasing inclination angle could contribute to the cooling and inerting effects. However, there was little effect on the cooling and inerting with an inclination angle less than 0°. This study can provide technical guidances for environmentally friendly fire extinguishing with LN₂ in a confined space.

Based on accident data from the China Chemical Accident Information Network, detailed information was obtained from 2657 hazardous chemicals road transportation accidents (HCRTAs) and 148 evacuations caused by these accidents that occurred in China from 2012 to 2020. The characteristics and the development trend of the present HCRTAs in China and the rate of emergency are obtained via statistical analysis. Based on the probability of evacuation scenarios via historical statistics, the social cost of labor loss value of participating emergency responders, and evacuees’ placement and transfer cost as the consequences of evacuation events, an evacuation event grading model based on social risk assessment is constructed. Evaluating and classifying the risk of evacuation events caused by HCRTAs (148), the results demonstrated that the social risk caused by emergency scenarios F_61 (leakage due to overturning of hazardous chemical vehicles, which led to evacuation) and F_91 (leakage due to rear-end of hazardous chemical vehicles, which led to evacuation) was higher than other emergency scenarios. To reduce the dangers caused by HCRTAs, the framework for improving the emergency response capacity of communities is discussed and analyzed based on five aspects, which comprise land use planning, city construction, education promotion, information construction, and the layout of emergency resources.

Designing a spreading strategy is one of the critical issues strongly affecting spreading efficiency in complex networks. In this paper, to improve the efficiency of information spreading in scale-free networks, we propose four hybrid strategies by combining two basic strategies, i.e. (i) the LS (in which information is preferentially spread from the large-degree vertices to the small-degree ones), and (ii) the SL (in which information is preferentially spread from the small-degree vertices to the large-degree ones). The objective in combining the two basic LS and SL strategies is to fully exploit the advantages of both strategies. To evaluate the spreading efficiency of the proposed four hybrid strategies, we first propose an information spreading model. Then, we introduce the details of the proposed hybrid strategies that are formulated by combining LS and SL. Third, we build a set of scale-free network structures by differently configuring the relevant parameters. In addition, finally, we conduct various Monte Carlo experiments to examine the spreading efficiency of the proposed hybrid strategies in different scale-free network structures. Experimental results indicate that the proposed hybrid strategies are effective and efficient for spreading information in scale-free networks.