Search

In recent years, the accident rate of urban rail transit PPP (public–private partnerships) project under construction has been relatively high, and the issue of security risks has attracted great attention from all walks of life. Therefore, it is necessary to identify, analyze, and evaluate the issue of security risks of the urban rail transit PPP project. This paper takes the PPP project of urban rail transit as the object. Through offline interviews and surveys and online questionnaires, this paper focuses on identifying and analyzing the risks brought by the introduction of PPP mode to the urban rail transit project and its action mechanism. The risk evaluation method based on Bayesian network model is studied, which is described from three dimensions: risk occurrence probability, risk reasoning, and risk sensitivity. Finally, an example of Xuzhou Metro Line 3 is given to verify the feasibility of the proposed method. This study provides a reference basis for relevant practitioners and promotes the healthy development of the industry. [ABSTRACT FROM AUTHOR]

[Display omitted] • Ru adsorption mechanism regulated by OH concentration of silica surface was computed. • Ru adsorption prefers surface O-H oxidative addition on the hydroxylated surface. • Stable configuration of adsorbed Ru atoms after H 2 desorption depends on surface hydroxyls. • Singly adsorbed Ru atom has the highest stability on the partially hydroxylated surface. • Metal-support interaction affects the dynamic process of particles dispersion and deactivation. To understand the metal–support interaction of oxide supported transition metal catalysts, we computed the adsorption structures and energies of ruthenium on the idealized SiO 2 (0 0 1) surfaces with full (OH, 100%), partial (OH, 50%) surface hydroxyl and without surface hydroxyl (OH, 0%) at different ruthenium loading. On the fully (up to 9Ru) and partially (up to 6Ru) hydroxylated surfaces, ruthenium adsorption prefers surface O-H oxidative addition and forms regularly distributed Ru(H) 2 species. After the reductive and re-combinative desorption of H 2 , the adsorbed ruthenium atoms prefer structures with aggregated 2Ru dimeric units on the fully hydroxylated surface, while structures of remote and dispersed singly adsorbed Ru atoms on the partially hydroxylated surface. On the hydroxyl free surface (up to 6Ru), the adsorbed ruthenium atoms prefer three-dimensional aggregated structures, which become more stable with the increase of ruthenium loading. This indicates the surface hydroxyl dependent ruthenium adsorption on SiO 2 (0 0 1), and this finding is important for understanding the structure, stability and activity of silica supported ruthenium catalysts and catalysis. [ABSTRACT FROM AUTHOR]