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After primary and secondary recovery of tight reservoirs, it becomes increasingly challenging to recover the remaining oil. Therefore, improving the recovery of the remaining oil is of great importance. Herein, molecular dynamics simulation (MD) of residual oil droplet movement behavior under CO2 displacement was conducted in a silica nanopores model. In this research, the movement behavior of CO2 in contact with residual oil droplets under different temperatures was analyzed, and the distribution of molecules number of CO2 and residual oil droplets was investigated. Then, the changes in pressure, kinetic energy, potential energy, van der Waals' force, Coulomb energy, long-range Coulomb potential, bond energy, and angular energy with time in the system after the contact between CO2 and residual oil droplets were studied. At last, the g(r) distribution of CO2–CO2, CO2-oil molecules, and oil molecules-oil molecules at different temperatures was deliberated. According to the results, the diffusion of CO2 can destroy residual oil droplets formed by the n-nonane and simultaneously peel off the n-nonane molecules that attach to SiO2 and graphene nanosheets (GN). The cutoff radius r of the CO2–CO2 is approximately 0.255 nm and that of the C–CO2 is 0.285 nm. The atomic force between CO2 and CO2 is relatively stronger. There is little effect caused by changing temperature on the radius where the maximum peak occurs in the radial distribution function (RDF)-g(r) of CO2–CO2 and C–CO2. The maximum peak of g(r) distribution of the CO2–CO2 in the system declines first and then rises with increasing temperature, while that of g(r) distribution of C–CO2 changes in the opposite way. At different temperatures, after the peak of g(r), its curve decreases with the increase in radius. The coordination number around C9H20 decreases, and the distribution of C9H20 becomes loose. [ABSTRACT FROM AUTHOR]

Objective: To determine the alkaloids content of Pinellia ternate in different growing time for finding out the best harvest time., Methods: The alkaloid was extracted by chloroform from Pinellia ternate and tested at 417 nm with the spectroscopy by acid dye. The result was analyzed in One-Way ANOVA., Results: The calibration curve of alkaloid was linear( r = 0.9989). The recovery rate was perfect (100.1%). The alkaloids content in different growing time had very significant difference ( F = 12.789, P < 0.01)., Conclusion: This method is simple and quick. The alkaloids content in whole seedling stage is higher than that in other growing stages, while the mean total alkaloids output per plant is the highest in intensive seedling-downfallen stage which is considered as the best harvest time.