Airline maintenance operations affect the potential for flight delays and can also affect flight safety if signals of technical problems are missed or misinterpreted. In this paper, we use a probabilistic risk analysis model, represented by an influence diagram, to quantify the effect of an airline’s maintenance policy on delays, cancellations and in-flight safety. The model represents the lead...

Let η = (η1, η2, . . . , ηt) and ν = (ν1, ν2, . . . , νt) be two sequences of nonnegative integers. (Append zeros if necessary to the end of the shorter sequence so that they are the same length.) We say that ν is majorized by η if ∑j l=1 νl ≤ ∑j l=1 ηl for all 1 ≤ j ≤ t and tl=1 νl = ∑t l=1 ηl. We write ν 1 η. Let Γ = (V,E) be a graph where V is a finite vertex set and E ⊆ V ×V is an edge set....

“La maniere d'enoncer vulgaire regarde plustost les individus, mais celle d'Aristote a plus d'egard aux idées ou universaux. Car disant ‘tout homme est animal’, je veux dire que tous les hommes sont compris dans tous les animaux; mais j'entends en même temps que l'idée de l'animal est comprise dans l'idée de l'homme. L'animal comprend plus d'individus que l'homme, mais l'homme comprend plus d'i...

As they descend, the autorotating seeds of maples and some other trees generate unexpectedly high lift, but how they attain this elevated performance is unknown. To elucidate the mechanisms responsible, we measured the three-dimensional flow around dynamically scaled models of maple and hornbeam seeds. Our results indicate that these seeds attain high lift by generating a stable leading-edge vo...

The classical Hurwitz theorem says that if n first “harmonics” (2n+1 Fourier coefficients) of a continuous function f(x) on the unit circle are zero, then f(x) changes sign at least 2n + 1 times. We show that similar facts and its converse hold for any function that are orthogonal to a Chebyshev system. These theorems can be extended for convex curves in d-dimensional Euclidean space. Namely, i...

For a finite multigraph G, the reliability function of G is the probability RG(q) that if each edge of G is deleted independently with probability q then the remaining edges of G induce a connected spanning subgraph of G; this is a polynomial function of q. In 1992, Brown and Colbourn conjectured that for any connected multigraph G, if q ∈ C is such that RG(q) = 0 then |q| ≤ 1. We verify that t...

Résumé L’alignement multiple de séquences constitue un outil central pour de nombreuses études en biologie moderne. Plusieurs algorithmes existent, basés sur différentes heuristiques. Nous présentons ici Plasma, un nouvel algorithme utilisant le principe de la programmation dynamique, appliqué à des blocs de séquences. Plasma a été testé sur l’ensemble des jeux d’essais de Balibase. Les premier...

|We present an eecient and precise numerical method in computational complexity and reliability to compute the number of zeros of a real polynomial in the unit disk.