As special ad-hoc networks, vehicular ad-hoc networks (VANETs) support vehicles to communicate with each other via opportunistic wireless links. In order to protect privacy of drivers, vehicles registered in VANETs are required to authenticate and communicate with surrounding vehicles or roadside infrastructure anonymously. However, due to high-speed driving and wireless environment, it is vital to propose a privacy protection scheme that is able to balance security and efficiency. Consequently, this paper proposes an anonymous authentication scheme in VANETs (AAAS). Specifically, we add region trust authority to provide more efficient anonymous authentication service for vehicles. Subsequently, group signature mechanism is adopted to achieve anonymity and conditional privacy. Moreover, security and performance analysis show that AAAS has higher security and efficiency.

The structural characteristics of coal at the molecular level are important for its efficient use. Bituminous coal from the Baozigou Coal Mine is investigated, using elemental analysis, 13C nuclear magnetic resonance, X-ray photoelectron spectroscopy, and Fourier transform infrared. The molecular structure was determined. The aromatic compounds of bituminous coal molecules are primarily two- and three-ring structures, and the aliphatic structures are primarily in the form of methyl, ethyl side chains, and naphthenic hydrocarbons. The ratio of aromatic bridge carbon to peripheral carbon in the molecular structure is 0.279. Oxygen atoms in the form of carbonyl, phenolic hydroxyl and C–O, and nitrogen atoms in pyrroles. Thus, the average structure model of bituminous coal macromolecules was constructed; the molecular formula was C169H128O10N2S, and the molecular weight was 2378. The aromatic structural units in the macromolecular structure of coal include four naphthalenes, three anthracenes, two tetracenes, and heteroatoms in the form of three carbonyl groups, one phenolic hydroxyl group, one pyrrole, and one pyridine. The structure optimization and annealing kinetic simulation of a single macromolecular structure model were performed. Chemical bonds such as bridge bonds and aliphatic bonds were found to be twisted, and π–π interactions between the aromatic sheets in the molecule produced adjacent aromatic sheets. This arrangement tends to be approximately parallel, and the total energy decreases from 6713.401 to 2667.595 kJ/mol, among which the bond stretching energy and van der Waals energy dominate. We used 20 bituminous coal macromolecular models to construct aggregated structural models. After optimization by molecular dynamics simulation, the macromolecules were constrained by the surrounding molecules, and the sheet-like aromatic carbon structures that were originally approximately parallel were distorted. The macromolecular structure model of bituminous coal constructed in this study provides a theoretical model basis for the optimal surfactant.

To improve the efficiency of coal dust removal by water spray technology, the addition of wetting agents in water becomes the main dust removal method. The influence of sodium dodecyl sulfate (SDS), sodium dodecyl sulfonate (SDDS), and sodium dodecylbenzene sulfonate (SDBS) on the wettability of coal dust is studied by experimental and molecular dynamics (MD) simulation. Measurement of the contact angle and surface tension was accomplished via relevant experiments for the three wetting agents, and their adhesion work, spreading work, and wetting work were also calculated. A preferred experimental method of conventional coal dust wetting agent is optimized. The wettability of the three wetting agents upon bituminous coal follows the trend: SDS > SDDS > SDBS. The simulation was performed based on MD to derive the intermolecular interaction energy, diffusion coefficient of water molecules, and water molecule count in the vicinity of the hydrophilic groups of the wetting agents. The wetting mechanism and performance of the wetting agent solution on bituminous coal were identified. The simulation results of the wetting performance of the wetting agents are consistent with the experimental results, which verifies the reliability of the simulation method. An easy, time-saving, and labor-saving MD simulation method is proposed, which provides a novel insight for choosing various wetting agents of coal dust.

To solve the problem of poor dust wettability during coal mine dust treatment, sodium dodecyl sulfate (SDS) and alkyl glycoside (APG1214) were selected for compounding. An efficient, environmentally friendly, economical wetting agent was prepared. First, through molecular dynamics simulation studies, it was determined that the tail group C of SDS and APG1214 was adsorbed on the surface of bituminous coal, and the head groups S and O were adsorbed on the surface of water. The simulation result is found to be consistent with the surfactant solution dust removal theory, which proves the confidence of simulation. Then, by comparing the interaction of water–SDS and APG1214–bituminous coal and water–bituminous coal systems and the number of hydrogen bonds, the wetting mechanism of the SDS and APG1214 solution on bituminous coal was revealed. Finally, the surface tension, contact angle, and wetting time of different SDS and APG1214 solutions were determined by experiments and they decreased with decreasing mass fraction of SDS at the same concentration. The surface tension of the SDS and APG1214 solution and the number of micelles affected the wettability of bituminous coal. The optimal concentration of the SDS and APG1214 solution was 0.7%, and the optimal ratio was SDS/APG1214 = 1:3.

To effectively improve the dust reduction rate of fine dust and prevent the occurrence of secondary dust, surfactant-charged water mist dust reduction technology is proposed. First, the water mist induction-charged atomization mechanism was perfected by an induction-charged spray experiment and the optimal atomization-charged voltage was determined to be 10 kV. Second, by surface tension and spray experiments on AEO-9-charged solutions, the lower the surface tension and viscosity of the solution, the better the atomization effect; the best atomization solution was 10 kV and 0.02% AEO-9. Finally, according to an electrostatic adsorption experiment, it was identified that there was an electrostatic interaction between coal dust and charged droplets. The contact angle experiment showed that the contact angle of the AEO-9 droplets decreased by 68.44% compared with water after 3 s of contact with coal dust. The wetting effect of bituminous coal was significantly improved by adding AEO-9 to water. A molecular simulation was used to study the molecular interaction mechanism among the H₂O, AEO-9, and bituminous coal molecules. The simulation results showed that AEO-9 was more active than water, it easily interacted with bituminous coal, and the hydrophilic group covered the surface of the bituminous coal molecules, which increased the electrostatic interaction between the water molecules and bituminous coal surface molecules. After adding AEO-9 to H₂O, the intermolecular interaction energy of the H₂O/AEO-9/bituminous coal system was enhanced more than that of the H₂O/bituminous coal system. This study provides the basis for the application of surfactant-charged water mist dust reduction technology.