Westphal, Stephan

[["dc.bibliographiccitation.firstpage","207"],["dc.bibliographiccitation.issue","2"],["dc.bibliographiccitation.journal","Mathematical Methods of Operations Research"],["dc.bibliographiccitation.lastpage","242"],["dc.bibliographiccitation.volume","83"],["dc.contributor.author","Thielen, Clemens"],["dc.contributor.author","Tiedemann, Morten"],["dc.contributor.author","Westphal, Stephan"],["dc.date.accessioned","2018-11-07T10:16:03Z"],["dc.date.available","2018-11-07T10:16:03Z"],["dc.date.issued","2016"],["dc.description.abstract","We consider an online knapsack problem with incremental capacity. In each time period, a set of items, each with a specific weight and value, is revealed and, without knowledge of future items, it has to be decided which of these items to accept. Additionally, the knapsack capacity is not fully available from the start but increases by a constant amount in each time period. The goal is to maximize the overall value of the accepted items. This setting extends the basic online knapsack problem by introducing a dynamic instead of a static knapsack capacity and is applicable to classic problems such as resource allocation or one-way trading. In contrast to the basic online knapsack problem, for which no competitive algorithms exist, the setting of incremental capacity facilitates the development of competitive algorithms for a bounded time horizon. We provide a competitive analysis of deterministic and randomized online algorithms for the online knapsack problem with incremental capacity and present lower bounds on the competitive ratio achievable by online algorithms for the problem. Most of these lower bounds match the competitive ratios achieved by our online algorithms exactly or differ only by a constant factor."],["dc.description.sponsorship","German Research Foundation (DFG) [GRK 1703/1]"],["dc.identifier.doi","10.1007/s00186-015-0526-9"],["dc.identifier.isi","000374577700003"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/40957"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Springer"],["dc.publisher.place","Heidelberg"],["dc.relation.issn","1432-5217"],["dc.relation.issn","1432-2994"],["dc.title","The online knapsack problem with incremental capacity"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","35"],["dc.bibliographiccitation.issue","1"],["dc.bibliographiccitation.journal","4OR"],["dc.bibliographiccitation.lastpage","57"],["dc.bibliographiccitation.volume","13"],["dc.contributor.author","Ide, Jonas"],["dc.contributor.author","Tiedemann, Morten"],["dc.contributor.author","Westphal, Stephan"],["dc.contributor.author","Haiduk, Felix"],["dc.date.accessioned","2018-11-07T10:00:21Z"],["dc.date.available","2018-11-07T10:00:21Z"],["dc.date.issued","2015"],["dc.description.abstract","In the veneer cutting industry tree trunks are peeled into thin veneer strips which are cut, glued together, and pressed into bentwood pieces for seats, backrests, etc. In this work, a model for optimizing the inherent cutting problem with respect to resource efficiency is presented. Especially the heterogeneous quality of the wood renders existing models for classic cutting stock problems useless and calls for a new modeling approach. By means of the model presented in this paper, the problem is solved to optimality for real-world instances in reasonable time and applicable solutions are generated. Furthermore, in order to deal with uncertainties in the wood quality, the approach of robust optimization is applied to the problem. Robust optimization is an important tool to deal with uncertainties in the formulation of mathematical optimization models. Different concepts of robustness have been provided in the literature, one of which is the concept of minmax robust efficiency for uncertain multi-objective optimization problems. The concept of minmax robust efficiency is applied to a simplified version of the problem, robust efficient solutions are calculated, and the paper concludes with the discussion of the benefit of these solutions."],["dc.identifier.doi","10.1007/s10288-014-0265-4"],["dc.identifier.isi","000351136300003"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/37788"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Springer"],["dc.publisher.place","Heidelberg"],["dc.relation.issn","1614-2411"],["dc.relation.issn","1619-4500"],["dc.title","An application of deterministic and robust optimization in the wood cutting industry"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dspace.entity.type","Publication"]]