Marco Ghirardi

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A hybrid heuristic method for combinatorial optimization problems is proposed that combines di erent classical techniques such as tree search procedures, bounding schemes and local search. The proposed method enhances the classic beam search approach by applying to each partial solution corresponding to a node selected by the beam, a further test that(More)
We consider the two machine total completion time flow shop scheduling problem. This problem is known to be NPHard in the strong sense. An improved Lagrangean relaxation approach is proposed. Two new dominance criteria are introduced to curtail the enumeration tree. A branch-and-bound algorithm capable of solving to optimality medium size problem instances(More)
BACKGROUND We evaluated the contribution of ultrasound (US) in detecting breast cancer in women with dense breasts and negative mammograms. METHODS 9157 (35.8%) of 25,572 self-referring women during 2000-2007 had BI-RADS D3-4 negative mammograms - all were screened with bilateral US. RESULTS US detected 37 cancers - incremental cancer detection rate(More)
Surveillance of interval cancers (IC) provides a measure of breast screening efficacy. Increased breast density is a predictor of breast cancer risk and of the risk of IC in screening. Improving screening sensitivity in women with dense breasts, through adjunct ultrasound (US), may potentially reduce IC; however this has not been proven. We report on(More)
This paper deals with a Hub Location Problem arising in Telecommunication Network Design. The considered network presents two different kinds of nodes: access nodes, that represent source and destination of traffic demands but cannot be directly connected, and transit nodes, that have no own traffic demand but collect traffic from access nodes and route it(More)
Although the phylogeography of European mammals has been extensively investigated since the 1990s, many studies were limited in terms of sampling distribution, the number of molecular markers used and the analytical techniques employed, frequently leading to incomplete postglacial recolonisation scenarios. The broad-scale genetic structure of the European(More)
In part II of this group of papers, the control of the gait of a biped robot during rectilinear walk was considered. The modeling approach and simulation, using Kane’s method with implementation leveraged by Autolev, a symbolic computational environment that is complementary, was discussed in part I. Performing turns during the walk is technically more(More)
In this paper, the problem of optimizing the performances of a distributed supply chain is faced by means of as decentralized architecture. In particular, a general scheme for an Lagrangian algorithm, based on Lagrangian relaxation of the precedence constraints, is presented. In this framework, the trade-off between the production cost of each node of the(More)