In the preparation of monocyclic benzenes by catalytic pyrolysis of lignin, how to break the bonds of pyrolysis macromolecules into small molecules is the key point for the transformation. In this work, density functional theory was used to explore the mechanism on catalytic pyrolysis of the β-O-4-type lignin dimer and the effect of H protons derived from solid acid catalysts during the pyrolysis process. The results indicate that C β −O bond cleavage is the main pathway for macromolecular breaking. When the H proton attacks the protonation site O13, the bond level of the C β −O bond decreases from 0.911 to 0.674 and the dissociation energy decreases from 210 to 179 kJ/mol. Phenol (P1), p-hydroxybenzaldehyde (P2), and p-hydroxyacetophenone (P5) are the main products of the subsequent pyrolysis pathways based on C β −O bond homolysis because of their more competitive formation pathways. The attack of H proton on O13 inhibits the formation of phenol, and it does not participate in the subsequent reaction pathways R7-1, R7-2, R7-3, and R7-4. P-hydroxybenzaldehyde (P2), p-hydroxyacetophenone (P5), and ethanol (P3) are produced because of the promotion of the preliminary pathway R7. It is found that H protons can weaken the C β −O bond and promote the formation of small molecule compounds by lignin pyrolysis macromolecular components.
The hybrid simulation (HS) is a cost-effective and promising method for investigating the seismic performance of structures. This paper proposes a model updating method for HS to improve incomplete boundary conditions and model error, and develops criteria to select the updated parameters. First, an actual HS model updating is conducted to verify the effectiveness of uniform design as a parameter estimation method. This experiment shows that parameter sensitivity has a significant relationship with the update effect. Then, the Sobol global sensitivity analysis (GSA) method is applied to the HS model updating to obtain the sensitivity indices of parameters that change with time, which provides a sound basis for parameter selection and the determination of the search range. Following this, a whole-structure module for dynamic time history analysis is proposed to improve the boundary conditions, simplify the implementation, and refine the numerical models. The errors in six boundary conditions of the traditional HS are then analyzed. The proposed method of model updating based on GSA is then obtained by integrating the above ideas. In the case of multiple inputs of ground motion, four strategies are developed to verify the effectiveness of the method.The results of a total of 216 numerical cases under different working conditions show that the proposed method can improve the accuracy of HSs and the identified parameters.
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