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Surfactants are widely used in the tertiary recovery of oilfields， and it is of great significance to study the mechanism of surfactant flooding from the microscopic point of view. In recent years， molecular dynamics （MD） simulation has become essential for oil and gas field development research. The use of MD simulation to study surfactants has become a hot spot. Through MD simulation， the numerical solutions of Newton’s equations are calculated for all the moving particles in the system， and the change in atomic positions with time is analyzed， from which some laws are found. MD simulation can be used to study the microscopic behavior of surfactant molecules to explore the properties of surfactant molecules and the microscopic flooding mechanism. MD simulation of the movement and aggregation state of surfactants at the interface and the analysis of the influence of surfactant molecules at the interface on the interfacial system are of some guiding significance for the field application of surfactants. To this end， based on the principle overview of MD simulation， firstly， the force field， boundary conditions， system types， and numerical algorithms in MD simulation are summarized； secondly， the microscopic mechanisms of MD simulation of surfactant flooding are highlighted， including the reduction of oil-water interfacial tension， the change in surface wettability， the increase in interfacial charge and emulsification， etc.； then， examples of the application of MD simulation in surfactant flooding are presented. Finally， the development directions of MD simulation technology in surfactant flooding are proposed， including the flooding environment similar to production， the design of new surfactants， the relationship between theory and experiment， the selection of molecular force field and potential energy model， and the research and development of composite and multifunctional integrated surfactants.

Objective To explore the effects of store-operated calcium entry(SOCE) on oxidized low-density lipoprotein (ox-LDL)-induced hyperpermeability in human umbilical vein endothelial cells(HUVECs). Methods HUVECs at passage 3 were divided into the control group and the ox-LDL(10, 25, 50 and 100 μg/mL) intervention groups (n=3) for the examination of transendothelial electrical resistance (TER). HUVECs cultured in slides were randomly divided into the control group, the ox-LDL 24 h group and the ox-LDL 48 h group. The distribution of F-actin and VE-cadherin were detected by immunofluorescence, and the protein content of VE-cadherin was detected by Western blotting. Incubated with calcium fluorescence probe (Fluo-3/AM), intracellular free Ca2+ concentration (control group, ox-LDLgroup, ox-LDL+2-APB group) and SOCE (control group, ox-LDL 24 h group, ox-LDL 48 h group) were detected by laser confocal microscopy. Results Low dose of ox-LDL(10, 25 μg/mL) exerted no effect on TER. High dose of ox-LDL (50, 100 μg/mL) also had no effect on TER within 6 h, but after 6 h showed no effect on TER. However, high dose of ox-LDL(50, 100 μg/mL) reduced the decrease of TER in 12 h (P < 0.05), and the decrease was more significant in 24 h and 48 h. After the incubation with ox-LDL(100 μg/mL) 24 h and 48 h, the expression level of VE-cadherin decreased(P < 0.05), while the form and distribution of F-action changed; Intracellular free Ca2+ concentration increased obviously which was interrupted by 2-APB the SOCE inhibitor (P < 0.05), and the 2-APB can decrease the effect of ox-LDL on TER. After incubation with ox-LDL(100 μg/mL) 48 h, the amplitude of SOCE decreased (P < 0.05). The descending artery flow velocity of SOCE showed a slightly decreased trend after incubation with ox-LDL 24 h and a more significant decrease in 48 h(P < 0.05). Conclusion Ox-LDL up-regulate the intracellular free Ca2+ concentration of vascular endothelial cells by extending the duration of SOCE to effect the arrangement of cytoskeleton and cell junction, which increases the cell permeability.

With the characteristics of high transmission delay and mobility, distributed time synchronization of underwa-ter sensor networks can be very challenging. The existing works cannot get high accuracy, because most of them ignore the long transmission latency, or dynamic changing tra ission delay caused by the mobility. A mobility model was built considering the effect of mobility and long transmission latency on time synchronization, and a time synchronization parameters equation was formed according to the mobili model. Thus, based on the equation, a time synchronization algorithm (MM-sync) was proposed. The experiment results show that MM-sync can reduce the consumption of energy, and can get higher accuracy than state-of-art solutions in high density underwater sensor networks with rapid movement.

With the characteristics of high transmission delay and mobility, distributed time synchronization of underwa-ter sensor networks can be very challenging. The existing works cannot get high accuracy, because most of them ignore the long transmission latency, or dynamic changing tra ission delay caused by the mobility. A mobility model was built considering the effect of mobility and long transmission latency on time synchronization, and a time synchronization parameters equation was formed according to the mobili model. Thus, based on the equation, a time synchronization algorithm (MM-sync) was proposed. The experiment results show that MM-sync can reduce the consumption of energy, and can get higher accuracy than state-of-art solutions in high density underwater sensor networks with rapid movement.