Microbiologically corrosion is a critical factor contributing to the degradation of marine engineering infrastructure.Electrochemical methods and slow strain rate tensile(SSRT) tests were employed to evaluate the effect of cathodic protection (CP) on the corrosion behavior of X70 pipeline steel in marine environments containing sulfate⁃reducing bacteria (SRB).Together with microstructural characterization,the stress corrosion cracking(SCC) mechanism of X70 steel in SRB⁃containing marine environments was analyzed.The results indicate that CP potentials of -0.775,-0.850 V promoted SRB growth.When the CP potential reached -1.000 V,it not only promoted the proliferation of SRB but also accelerated their transition into the decline phase.In the absence of applied stress,the optimal CP potential for X70 steel in SRB⁃containing marine environments was -0.850 V.Without CP,the SCC mechanism of X70 steel was a hybrid mode involving anodic dissolution induced by the marine environment and hydrogen⁃induced cracking caused by SRB.At CP potentials of -0.775,-0.850 V,the SCC mechanism was dominated by SRB⁃induced hydrogen⁃induced cracking.When the CP potential was -1.000 V,the SCC mechanism was a hybrid mechanism jointly induced by anodic dissolution caused by the marine environment and hydrogen⁃induced cracking induced by the CP potential.The synergistic effect of SRB and CP significantly increased the hydrogen embrittlement susceptibility of X70 steel in marine environments.

The Tb coordination complex [Tb(H₂O)₈]?(L)?2(4,4'?bipy)?3H₂O（complex 1） was synthesized by hydrothermal reaction of sodium 1,3,6?naphthalene trisulfonate (Na₃L) and 4,4'?bipy (4,4'?bipy) with Tb(NO₃)₃?6H₂O. The molecular structure and composition of complex 1 were characterized by single crystal X?ray diffraction, FT?IR spectroscopy, thermogravimetric analysis and elemental analysis. Thermal stability and fluorescence emission properties of complex 1 were also evaluated. The results indicate that Tb³⁺ is eight?coordinated in a tetragonal antiprismatic coordination configuration and coordinates with eight H₂O molecules to form [Tb(H₂O)₈]³⁺.L^3- does not coordinate with metal ion, but only balances the positive charge in the molecule. The formation of hydrogen bonds between the sulfonic acid group of the L^3- and the coordinating H₂O molecule connects the [Tb(H₂O)₈]³⁺ and the L^3- to form a one?dimensional chain structure,which in turn expands into a two?dimensional lamellar structure.The fluorescence emission peaks of complex 1 at 395，453 nm are the characteristic peaks of Na₃L, and the emission peaks at 545,601，641 nm are the characteristic peaks of Tb³⁺.

Stress sensitivity is one of the factors influencing fracture net deliverability of multistage fractured horizontal well for tight sandstone gas reservoirs. Based on seepage characteristic of tight sandstone gas reservoir, seepage law after fracturing work and steady seepage theory, flowing resistance method was used to derive fracture net deliverability correlation considering stress sensitivity of multistage fractured horizontal well for tight sandstone gas reservoirs, and then the correlation was used to analyze fracture parameters and stress sensitivity level on gas production rate. The results indicate that with increasing fracture flow conductivity and fracture net permeability, gas production is gradually increased, but the increase is slowed down. The unimpeded flow increases gradually with the increase of fracture half length, and increases rapidly with the increase of fracture conductivity. Therefore, in order to improve gas reservoir productivity, it is more significant to improve fracture halflength than fracture flow conductivity. The greater the stress sensitivity coefficient is, the greater the permeability decreases with the production, and the more the productivity of the gas well decreases.

The Prins condensation intrinsic kinetics of formaldehyde with isopentene was studied with the strong acidic cationexchange resin as catalyst. The formaldehyde react with isopentene under 2.0 MPa of N2 pressure and at 333～373 K in a batch reactor. The kinetic model was put forward with a reasonable assumption. The kinetics parameters were obtained using nonlinear regression methods. The results show that the positive reaction rate constant and the reverse reaction rate constant are both increased when the reaction temperature increasing. The activation energy is determined as 31.74 kJ/mol for the positive reaction and 85.04 kJ/mol for the reverse reaction. The preexponential factors of the positive reaction and the reverse reaction is respectively 6.866×103 and 3.75×1010; the kinetic model is simulated.