2011
Authors
Coelho, J; Vanhoucke, M;
Publication
EUROPEAN JOURNAL OF OPERATIONAL RESEARCH
Abstract
This paper reports on a new solution approach for the well-known multi-mode resource-constrained project scheduling problem (MRCPSP). This problem type aims at the selection of a single activity mode from a set of available modes in order to construct a precedence and a (renewable and non-renewable) resource feasible project schedule with a minimal makespan. The problem type is known to be NP-hard and has been solved using various exact as well as (meta-)heuristic procedures. The new algorithm splits the problem type into a mode assignment and a single mode project scheduling step. The mode assignment step is solved by a satisfiability (SAT) problem solver and returns a feasible mode selection to the project scheduling step. The project scheduling step is solved using an efficient meta-heuristic procedure from literature to solve the resource-constrained project scheduling problem (RCPSP). However, unlike many traditional meta-heuristic methods in literature to solve the MRCPSP, the new approach executes these two steps in one run, relying on a single priority list. Straightforward adaptations to the pure SAT solver by using pseudo boolean non-renewable resource constraints has led to a high quality solution approach in a reasonable computational time. Computational results show that the procedure can report similar or sometimes even better solutions than found by other procedures in literature, although it often requires a higher CPU time.
2011
Authors
Santos, V; Amaral, L; Mamede, H;
Publication
Proceedings of the 6th Iberian Conference on Information Systems and Technologies, CISTI 2011
Abstract
The organizations ability to make effective use of information technology and to focus on innovation and creativity are recognized as being important. The perspective of using creativity techniques or some adaptations, to help innovation in the information systems area seems to be promising. In this article we propose a strategy for introduce creativity in the information systems planning in order to build more agile and efficient information systems, allowing therefore more competitive business. © 2011 AISTI.
2011
Authors
Santos, V; Amaral, L; Mamede, H;
Publication
SISTEMAS E TECNOLOGIAS DE INFORMACAO, VOL I
Abstract
2011
Authors
Santos, V; Amaral, L; Mamede, H;
Publication
ENTERPRISE INFORMATION SYSTEMS, PT 2
Abstract
The global competitiveness and the organizations ability to make effective use of information technology and to focus on innovation and creativity are recognized as being important. The perspective of using creativity techniques or some adaptations, to help innovation in the area of information systems seems to be promising. In this article we propose a strategy for the introduction of creativity in the information systems planning in order to build more agile and efficient information systems, allowing therefore more competitive business.
2011
Authors
Barbosa, SM;
Publication
JOURNAL OF CLIMATE
Abstract
Long-term variability in global sea surface temperature (SST) is often quantified by the slope from a linear regression fit. Attention is then focused on assessing the statistical significance of the derived slope parameter, but the adequacy of the linear model itself, and the inherent assumption of a deterministic linear trend, is seldom tested. Here, a parametric statistical test is applied to test the hypothesis of a linear deterministic trend in global sea surface temperature. The results show that a linear slope is not adequate for describing the long-term variability of sea surface temperature over most of the earth's surface. This does not mean that sea surface temperature is not increasing, rather that the increase should not be characterized by the slope from a linear fit. Therefore, describing the long-term variability of sea surface temperature by implicitly assuming a deterministic linear trend can give misleading results, particularly in terms of uncertainty, since the actual increase could be considerably larger than the one predicted by a deterministic linear model.
2011
Authors
Scotto, MG; Barbosa, SM; Alonso, AM;
Publication
JOURNAL OF APPLIED STATISTICS
Abstract
Time series of daily mean temperature obtained from the European Climate Assessment data set is analyzed with respect to their extremal properties. A time-series clustering approach which combines Bayesian methodology, extreme value theory and classification techniques is adopted for the analysis of the regional variability of temperature extremes. The daily mean temperature records are clustered on the basis of their corresponding predictive distributions for 25-, 50- and 100-year return values. The results of the cluster analysis show a clear distinction between the highest altitude stations, for which the return values are lowest, and the remaining stations. Furthermore, a clear distinction is also found between the northernmost stations in Scandinavia and the stations in central and southern Europe. This spatial structure of the return period distributions for 25-, 50- and 100-years seems to be consistent with projected changes in the variability of temperature extremes over Europe pointing to a different behavior in central Europe than in northern Europe and the Mediterranean area, possibly related to the effect of soil moisture and land-atmosphere coupling.
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