29,829 research outputs found

    Introducing new constructs for data modelling and column generation in LP modelling languages

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    Through popular implementation of structured query language (SQL) and query-by-example(QBE) relational databases have become the de-facto industry standard for data modelling.We consider the indices, sets, and the declarative form of Linear Programming (LP) modelling languages and introduce new constructs which provide direct link to the database systems. The models constructed in this way are data driven and display a dynamicstructure. We then show how this approach can be naturally extended to include column generation features stated in procedural forms within an otherwise declarative modelling paradigm

    Sets and indices in linear programming modelling and their integration with relational data models

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    LP models are usually constructed using index sets and data tables which are closely related to the attributes and relations of relational database (RDB) systems. We extend the syntax of MPL, an existing LP modelling language, in order to connect it to a given RDB system. This approach reuses existing modelling and database software, provides a rich modelling environment and achieves model and data independence. This integrated software enables Mathematical Programming to be widely used as a decision support tool by unlocking the data residing in corporate databases

    Influence of Alignment on the Scattering Properties Atmospheric Mineral Dust

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    We carry out an investigation of the influence of particle alignment on the scattering properties of mineral dust layers. Our modelling indicates that in addition to modifying optical thickness, the alignment can significantly alter the scattering properties, including polarization. Influence of the alignment on remote sensing retrievals is also examined, and it is concluded that satellite and to a lesser extent sun photometry retrievals would be significantly affected
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