Preventive maintenance is required to keep critical systems available at reasonable costs. Instead of applying the traditional experience-based approach of statistical analysis of failure data, the present paper proposes to adopt a predictive maintenance policy that relies on detailed knowledge of the physical failure mechanisms. A structured scheme for this approach is presented. Then three ca...

We describe a simulator for modeling complex control dynamics in optical line systems involving the interaction of multiple transmission, control, and monitoring elements in response to channel changes, component failure, and recovery events.

ieter Bruegel el Viejo (Breda 1525-Bruselas 1569) es una figura apital de la pintura flamenca del siglo xvi cuyo genio se a equiparado a El Bosco. Especializado en paisajes poblados e campesinos, el pintor buscó la inspiración en el folclore, os refranes populares y los trabajos cotidianos, reflejando elmente la vida del pueblo flamenco. Aunque también reaizó obras religiosas, Bruegel es el pin...

2',3'-Dihydroxy-4,4'-dimethoxychalcone (1) and 2',3',4-trihydroxy-4'-methoxy-chalcone, two new chalcones, were isolated from propolis from El Salvador. The compounds showed significant antibacterial and antifungal activity and moderate toxicity to Artemia salina nauplii.

1.1 Définitions élémentaires Définition 1. Soit P ∈ k[X ] et a ∈ k. On dit que a est une racine de P si P (a) = 0, ou de manière équivalente si X − a divise P . On appelle multiplicité de a le plus grand entier μ tel que (X − a) divise P . Proposition 1. Si P ∈ k[X ] admet a1, . . . , al pour racines, de multiplicités respectives μ1, . . . , μl, alors il existe Q ∈ k[X ] tel que P = Q∏(X − ai)i...