RESUMO
Redundant programmable electronic systems are commonly used in many industrial processes for safety protection and high availability process control. Common-cause failures can significantly reduce the benefits of the redundancy designed into this equipment. To improve on this situation, a number of qualitative design rules for reducing common cause failures have been put forth. However, these rules have not previously been subjected to quantitative verification. It is important to understand the magnitude of common cause failures and how this varies with design changes. This information can be used to show how system designs can be improved by lowering common cause failure rates. A stress-strength simulation was created to simulate the failures of a programmable electronic system under different design scenarios and the common cause failure rate was computed for each case. The simulation results not only confirm that the qualitative design rules lowered common cause failure rates but also provide some quantitative assessment of how large the improvements can be in various cases.
RESUMO
The authors review the literature in relation to a detailed study of an ovarian arrhenoblastoma operated on in a young patient who subsequently became pregnant twice, one of these pregnancies developing to full term. This review makes it possible to formulate certain anatomopathological ideas, and above all makes it clear that complete endocrine studies are infrequently carried out. It has been shown in cases of arrhenoblastoma that some of the anomalies of steroidogenesis are secondary to the enzyme disorders, the impression being that, with this kind of tumour, the tumour parenchyma begins to secrete like a normal testicle.
