The effect of aryltin compounds (Ar,Sn and Ar,SnCI) on the growth of Ceratocystis ulmi, the causative agent of Dutch elm disease, was studied in shake culture. In all cases, the triaryltins were more effective than the tetra-aryltins as inhibitors of C. ulmi in vitro. Furthermore, substitution on the phenyl ring at the meta-and para-positions in the triaryltins did not have a major effect on the biocidal activity for the substituted triaryltins. Quantitative structure-activity relationships (QSARs) gave support to the idea that the species responsible for the inhibition of the fungus is the triaryltin cation. The QSARs further suggest that the interaction of the triaryltin cation with the fungal cell wall of C . ulmi is by a non-specific mechanism.
According to 62 field fault data from a certain type of 8 NC machine tools, maintainability distribution model is established based on the repair time. Hypothesis testing shows that the repair times of NC machine tools fit mathematical model of lognormal distribution. This provides the basis for maintainability assessment of NC machine tool as well as the development of maintenance strategy in the future.
Dependent failures of machines may take many forms. Interactive failure is one type of the dependent failures happening among multiple subsystems. The interactive coefficient is represented by the degree of interaction between two subsystems, but it cannot be estimated in intricate interactive relationship among multiple subsystems by now. In order to solve the problem, the failure chains of the interactive failure are classified into five types in this paper and all the elements in it are defined. Then the interactive coefficient models are developed for all failure chains according to the relationship among the interactive failure rate, the independent failure rate and the dependent failure rate. The estimation of the interactive coefficient is based on failure rate equation. The results offer a solution to the problem that the interactive coefficient of multiple systems cannot be calculated. These findings provide a method to predict and design the reliability of mechanical equipment more accuracy as well as guide to optimize scheduled for the maintenance of mechanical equipment.
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