The fracture damage of oil and gas pipelines usually initiates from micro?cracks. The weak magnetic detection method is of practical significance for the detection of microcracks in long distance oil and gas pipelines. However, the microstructure of pipeline microcracks is complex, and the traditional weak magnetic field detection model is difficult to achieve accurate quantitative calculation of pipeline microcracks. Based on the theory of magnetoelectric coupling, a mathematical model of weak magnetic signal of pipeline micro?crack is established. The weak magnetic signal of micro?crack under different excitation conditions is compared and analyzed. The propagation characteristics of micro?crack at different depths and the signal detection characteristics under different lifting values are analyzed and calculated. The results show that the weak magnetic signal generated by the microcrack is much larger than the geomagnetic field, and the difference increases as the increase of the stress value. The weak magnetic signal increases with the increase of stress value. When the critical point of microcrack propagation is reached, the magnetic energy is released due to microcrack propagation, and the weak magnetic signal decreases with the increase of stress value. After microcrack propagation, the magnetic sensitivity of the material decreases, but the linear characteristics are more obvious. The larger the crack depth is, the stronger the weak magnetic signal is, and the damage is more easily detected. With the increase of the lift value, the weak magnetic signal decreases exponentially, and the detection accuracy of the signal in the linear region is the highest.

The hydrocracking unit is a Class A fire hazard device, which can be susceptible to fire and explosion accidents due to equipment failure. Therefore, it is essential to identify and quantitatively analyze the risk factors. In this paper, qualitative HAZOP, steady-state simulation, dynamic simulation and FTA are combined. Taking process flow of the absorbing-stabilizing system of an actual hydrocracking unit in a refining company as an example, and the quantitative risk analysis is carried out for the deviation of "high column pressure" of the absorption and desorption column and "high column temperature" of the naphtha stabilisation column. With the help of Aspen Plus software, the steady-state and dynamic simulation under dangerous conditions is carried out, and the probability of the consequences of the dangerous accident is calculated by FTA method. The results show that this method can help experts understand the propagation process of the accident, master the safety response time of the personnel, which is conducive to the prevention and timely treatment of accidents, and effectively improve the intrinsic safety level of the hydrocracking units.

This paper studies the formation containment control algorithm for multiple spacecraft systems under actuator and sensor faults. Firstly, the orbit dynamics of the spacecraft is modeled and linearized. Then, an adaptive descriptor observer is designed to obtain the estimated values of system states as well as actuator and sensor faults. By adjusting the nonsingular matrix, the performance of the observer can be improved and the observer error can converge near the origin. Based on the estimated system states and actuator faults, formation containment controller is designed. The sufficient conditions for the convergence of formation error and observer error are obtained through Lyapunov analysis. Finally, the system performance under the designed algorithm is verified by a simulation example.

Template agent is an essential part in the synthesis of molecular sieves, which has great influence on the physical properties and catalytic properties of molecular sieves. SAPO?34 molecular sieve was synthesized by hydrothermal method using stainless steel tube as crystallization vessel. The effect of PEG?800 addition on crystallinity, morphology and acidity of molecular sieve was investigated, and its MTO catalytic performance was evaluated. The results show that the molecular sieve samples synthesized with TEAOH & PEG?800 as the composite template agent are thin plate?like, the crystallinity and acidity are suitable, and the longest catalytic life is 340 min. When the methanol conversion is above 95%, the selectivity of diolefins is up to 84.0%. It is also found that the thinner the crystal thickness of the lamellar molecular sieve, the better the catalytic performance.

Hierarchical porous Hβ molecular sieve with different structure and acidity were prepared by alkali treatment. XRD, SEM, N₂ physical adsorption and NH₃?TPD characterization methods were used to characterize molecular sieves before and after alkali treatment. With hierarchical porous Hβ molecular sieve as the carrier, the Ru?Hβ bifunctional catalysts were prepared by an equal volume impregnation method, and the benzene hydroalkylation reaction activity and stability were evaluated in a fixed bed reactor.The results show that Hβ molecular sieve can effectively increase the proportion of mesopores after being treated with a proper concentration of alkali, which is beneficial to improve the hydroalkylation activity and stability. At 2 MPa, 210 ℃ and a liquid hourly space velocity of 1 h^-1, when the Ru mass fraction is 0.2% (based on the mass of hierarchical porous Hβ molecular sieve), the dual?functional catalyst composed of hierarchical porous Hβ can achieve effective and stable operation. At the same time, the conversion rate of benzene is 54.32%, the selectivity of cyclohexyl benzene is 71.47%, and the stability of the catalyst does not decrease significantly within 280 h.