CEGI - Other Publications

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Browsing CEGI - Other Publications by Author "José Fernando Oliveira"
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    Cutting and packing
    ( 2013) Bennell,JA ; José Fernando Oliveira ; Waescher,G
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    The Dotted-Board Model: A new MIP model for nesting irregular shapes
    ( 2013) Toledo,FMB ; Maria Antónia Carravilla ; Cristina Ribeiro ; José Fernando Oliveira ; António Miguel Gomes
    The nesting problem, also known as irregular packing problem, belongs to the generic class of cutting and packing (C&P) problems. It differs from other 2-D C&P problems in the irregular shape of the pieces. This paper proposes a new mixed-integer model in which binary decision variables are associated with each discrete point of the board (a dot) and with each piece type. It is much more flexible than previously proposed formulations and solves to optimality larger instances of the nesting problem, at the cost of having its precision dependent on board discretization. To date no results have been published concerning optimal solutions for nesting problems with more than 7 pieces. We ran computational experiments on 45 problem instances with the new model, solving to optimality 34 instances with a total number of pieces ranging from 16 to 56, depending on the number of piece types, grid resolution and the size of the board. A strong advantage of the model is its insensitivity to piece and board geometry, making it easy to extend to more complex problems such as non-convex boards, possibly with defects. Additionally, the number of binary variables does not depend on the total number of pieces but on the number of piece types, making the model particularly suitable for problems with few piece types. The discrete nature of the model requires a trade-off between grid resolution and problem size, as the number of binary variables grows with the square of the selected grid resolution and with board size.
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    Operations research in agriculture: Better decisions for a scarce and uncertain world
    ( 2013) Maria Antónia Carravilla ; José Fernando Oliveira
    Operations Research/Management Science (OR/MS) can be described as the discipline of applying advanced analytical methods to help making better decisions and has been around in the agricultural and forestry management sectors since the fifties, approaching decision problems that range from more strategic sectorlevel planning to farm operation issues and integrated supply chain management. In this paper insights are given on the use of OR/MS in agriculture, illustrating them with cases drawn from the literature on this topic while keeping the descriptions accessible to uninitiated readers. The presence of OR/MS in Agriculture and Forest Management applications is already extensive but the potential for development is huge in times where resources are becoming increasingly scarce and more has to be done with less, in a sustainable way.