Operational Research

Borgwardt, Steffen; Brieden, Andreas; Gritzmann, Peter

doi: 10.1007/s12351-009-0041-ypmid: N/A

The present paper introduces and studies a new combinatorial clustering model for the consolidation of farmland. While the general problem turns out to be NP-hard even in quite restricted cases, the Size-restricted Minimum-k-Star Group Partition problem is solvable in polynomial time. Based on this tractability result, we derive a general approximation algorithm which, as the mathematical analysis and economic evaluation shows, performs well in theory and practice.

Crespo, Olivier; Bergez, J.; Garcia, F.

doi: 10.1007/s12351-009-0040-zpmid: N/A

Optimization by simulation of agricultural practices can help to improve irrigation water use efficiency. This work introduces an efficient hierarchical decomposition method to design irrigation management strategies that is modeled as a continuous stochastic problem. Various combinations of selection (greedy, Pareto-based), division (middle, pivot, maximization) and evaluation techniques (global, standard deviation) were tested. We present results of an 8-continuous-parameter irrigation strategies design. Two criteria were chosen to evaluate the different combinations: the achieved direct margin, and the number of simulation runs that were needed to reach it. Selection techniques impacted the resolution time, while the evaluation techniques impacted the direct margin efficiency. Based on the two former criteria, the trade-off combination of greedy selection, pivot partition and average value evaluation appeared to be the most efficient to design irrigation strategies.

Silva, Susana; Fidalgo, J.; Fontes, Dalila

doi: 10.1007/s12351-009-0045-7pmid: N/A

Energy policies in the European Union (EU) and its 27 member states respond to three main concerns namely energy security, economic development, and environmental sustainability. All the three “Es” are pursued simultaneously with some slight differences in emphasizing the mutual importance of these, in particular the cost factors. The legislation of the EU (e.g., ETS—Emission Trading Scheme, directives) increasingly guides the member states’ energy policies. However, energy policy directions are still made domestically, for example, on the support on renewable energy technologies. In this work, we look into distributed generation (DG), since it has been grown considerable in the past few years and can be used to partially fulfill renewable energy targets. The policy makers have to make decisions about regulation directives, more specifically they have to change the current regulation in order to incentive the increase in DG. However, these decisions have not only economic impacts but also technical impacts that must be accounted for. In this regard, a decision aid tool would help the policy makers in estimating producer economic impacts, as well as power network technical impacts, of various possible regulation directives. Here, we propose an interactive decision aid tool that models the aforementioned impacts and thus, can be used by policy makers to experiment with different regulation directives before deciding on the ones to set.

Karetsos, Sotiris; Manouselis, Nikos; Costopoulou, Constantina

doi: 10.1007/s12351-009-0060-8pmid: N/A

Developing Web-based systems for agriculture and rural development requires the collaboration of experts from different scientific fields and backgrounds. Thus, it is crucial to ensure that the involved specialists have a common language that everybody understands. On the other hand, although the information and communication technologies (ICT) and particularly the Internet are drivers for overcoming the disadvantages of rural areas with respect to markets and suppliers, rural businesses are characterized by low ICT adoption and limited use of e-government services. In this light, this paper focuses on the analysis, design and deployment of an e-government observatory for rural small and medium enterprises (SMEs) according to the unified modeling language (UML)-based rational unified process (RUP) life cycle approach. The proposed observatory allows rural SMEs to find information both on e-government services offered in their region, as well as to have access to e-learning content on how they can use such services. The successful implementation and evaluation of the observatory, provides also useful contributions about modeling, analyzing, designing and documenting such systems using UML with rational unified process.

Zamani, Reza

doi: 10.1007/s12351-009-0073-3pmid: N/A

This paper presents a hybrid decomposition procedure for solving the resource-constrained project scheduling problem. The procedure finds an initial schedule for the project, and refines it through a decomposition process. This is performed through a refinement process which consists of (i) analyzing the initial schedule to find appropriate decomposition point(s), (ii) decomposing the associated project into appropriate subprojects, (iii) optimizing the subprojects by an efficient implicit enumeration technique, and subsequently (iv) integrating optimal sub-schedules to create a feasible schedule. This refinement process is aimed at reducing the makespan of the initial schedule. To achieve further reduction, the refined schedule is overrefined by a genetic algorithm. The results of computational experiments performed on 2,040 benchmark instances indicate that in a reasonable time the procedure can obtain solutions whose average percentage deviation from their associated best solutions in the litrature is 0.41.