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This paper presents a hierarchical Markov model to assess the reliability of a double-sided linear switched reluctance generator (DLSRG) system. The proposed reliability model can be applied to find the balance point of reliability assessment accuracy and model complexity. First, the dominant fault modes of the DLSRG system are highlighted to quantitatively obtain the operation states, survival or failure, with a novel failure criterion. Second, a hierarchical Markov model is adopted to build a systematic reliability model of the DLSRG system, wherein a state transition diagram can be built in the detailed description to constitute the graphical Markov reliability model. And then the solving process to get state probability matrix P(t) is intensively investigated. Notably, a reliability block diagram model is also built to compare with the hierarchical Markov model, whose results verify that the Markov model can capture the effect of fault-tolerance capability on system reliability. Moreover, it is expected that the one-level Markov model is the most suitable model for the DLSRG system for its ability of decreasing the model complexity and improving the assessment accuracy. Analytic investigation in conjunction with simulation and experimental measurements demonstrates the feasibility and validity of the proposed model. [ABSTRACT FROM AUTHOR]

The electron-rich Fe-based bulk catalysts are developed to promote the hydrodesulfurization (HDS) performance of dibenzothiophene (DBT). In this study, the Fe-Ti bulk catalyst was modified by the SO 4 2- species to investigate the dispersibility, acidity, electron effect, and isolation effect impacting on HDS performance for DBT. Besides, as sulfidation degree (SD) improves, more the coordinately unsaturated sites (CUSs) will be available for the DBT molecules to be adsorbed and desulfurized that is conducive to the improvement of HDS performance for DBT over Fe-based bulk catalysts. Eventually, compared with Fe-Ti bulk catalyst, the HDS rate of DBT has a remarkable increase from 7.8% to 29.9%, 41.5% to 65.0%, and 70.2% to 90.5% under the reaction temperature with 300, 320, and 340 °C upon the introduction of the SO 4 2- species for 0.3-SO 4 2-/Fe-Ti catalyst, respectively. On the one hand, the Ti species can improve the conversion of electrons to Fe species that form electron-rich Fe-based catalysts, resulting in the improvement of the Fe-based bulk catalysts activity. On the other hand, the addition of SO 4 2- species not only promote the SD by forming the Fe(III)-S and Fe1‐xS species but also strengthen the electron effect between Ti and Fe species, which is conducive to the improvement of HDS performance for DBT. In addition, the SO 4 2- species also worked as an "isolate agent", and can promote increasing the SD for this series of Fe-based bulk catalysts to improve the HDS rate of DBT. Thus, exploring the impact of SO 4 2- species on the HDS performance of Fe-based catalysts is a promising direction for the design and development of environmentally friendly and economical low-cost HDS catalysts in the field of fossil fuel processing. [Display omitted] • The impact of SO 4 2- on the HDS performance of dibenzothiophene were studied. • The electron-rich Fe-based bulk catalyst result in the improvement of HDS performance. • The SO 4 2- species worked as an "isolate agent" can increase the SD in Fe-based bulk catalysts. • The impact of reducibility and acidity on HDS in Fe-based bulk catalysts were studied. [ABSTRACT FROM AUTHOR]

In this work, a ternary hydrodesulfurization catalyst with fluorine introduced into the FeZn bimetallic active sites was prepared by a step-by-step incipient wetness impregnation. Among them, the sulfur removal ability increases gradually with the addition of F, and then tends to remain constant. Compared with FeZn catalyst, the maximum activity of the fluorinated catalyst can increase to 6 times at 613 K. It is found that the synergy effect exists in the ternary FeZnF species according to the characterization results. As a part of the active phase, not only the acidity of the catalyst was improved and the dispersion of metal species was optimized by F, but also the closed cycle of complex electron transfer among Fe-Zn-F was aggravated resulting in the weaken of Fe-O/Fe-S bond. Therefore, the sulfurization degree of FeZnF(x) was improved which leads to more active sites and noteworthy HDS activity. [Display omitted] • The ternary Fe-Zn-F was obtained by introducing the promoter F into the active sites. • The HDS activity was enhanced and the trend was increased and then remained invariant. • The electron transfer behavior among Fe, Zn and F was important to improve activity. • The acidity and dispersion played an auxiliary role in the amelioration of activity. [ABSTRACT FROM AUTHOR]