Browsing by Author "Diner, Öznur Yaşar"
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Bayesian and Graph Theory Approaches to Develop Strategic Early Warning Systems for the Milk Market
Authors:Gürpınar, Furkan; Bisson, Christophe; Diner, Öznur Yaşar
Publisher and Date:(SpringerVerlag Berlin, 2015)This paper presents frameworks for developing a Strategic Early Warning System allowing the estimatation of the future state of the milk market. Thus this research is in line with the recent call from the EU commission for tools which help to better address such a highly volatile market. We applied different multivariate time series regression and Bayesian networks on a predetermined map of relations between macro economic indicators. The evaluation of our findings with root mean square error ...

Contraction and deletion blockers for perfect graphs and Hfree graphs
Authors:Diner, Öznur Yaşar; Paulusma, Daniel; Picouleau, Christophe; Ries, Bernard
Publisher and Date:(Elsevier Science, 2018)We study the following problem: for given integers d k and graph G can we reduce some fixed graph parameter pi of G by at least d via at most k graph operations from some fixed set S? As parameters we take the chromatic number chi clique number omega and independence number alpha and as operations we choose edge contraction ec and vertex deletion vd. We determine the complexity of this problem for S = {ec} and S = {vd} and pi is an element of{chi omega alpha} for a number of subclasses of perfect ...

Contraction Blockers for Graphs with Forbidden Induced Paths
Authors:Diner, Öznur Yaşar; Paulusma, Daniel; Picouleau, Christophe; Ries, Bernard
Publisher and Date:(SpringerVerlag Berlin, 2015)We consider the following problem: can a certain graph parameter of some given graph be reduced by at least d for some integer d via at most k edge contractions for some given integer k? We examine three graph parameters: the chromatic number clique number and independence number. For each of these graph parameters we show that when d is part of the input this problem is polynomialtime solvable on P4free graphs and NPcomplete as well as W[1]hard with parameter d for split graphs. As split ...

On list kcoloring convex bipartite graphs
Authors:Diaz, Josep; Diner, Öznur Yaşar; Serna, Maria; Oriol, Serra
Publisher and Date:(Springer Nature, 2021)List kColoring (LikCol) is the decision problem asking if a given graph admits a proper coloring compatible with a given list assignment to its vertices with colors in {1, 2, …, k}. The problem is known to be NPhard even for k = 3 within the class of 3regular planar bipartite graphs and for k = 4 within the class of chordal bipartite graphs. In 2015 Huang, Johnson and Paulusma asked for the complexity of Li 3Col in the class of chordal bipartite graphs. In this paper, we give a partial answer ...

Strategic Early Warning System for the French milk market: A graph theoretical approach to foresee volatility
This paper presents a new approach for developing a Strategic Early Warning System aiming to better detect and interpret weak signals. We chose the milk market as a case study in line with the recent call from the EU Commission for governance tools which help to better address such highly volatile markets. Furthermore on the first of April 2015 the new Common Agricultural Policy ended quotas for milk which led to a milk crisis in the EU. Thus we collaborated with milk experts to get their inputs ...

Strategic Early Warning System for the French milk market: A graph theoretical approach to foresee volatility
This paper presents a new approach for developing a Strategic Early Warning System aiming to better detect and interpret weak signals. We chose the milk market as a case study, in line with the recent call from the EU Commission for governance tools which help to better address such highly volatile markets. Furthermore, on the first of April 2015, the new Common Agricultural Policy ended quotas for milk, which led to a milk crisis in the EU. Thus, we collaborated with milk experts to get their ...

Threefastsearchable graphs
Authors:Dereniowski, Dariusz; Diner, Öznur Yaşar; Dyer, Danny
Publisher and Date:(Elsevier Science Bv, 2013)In the edge searching problem searchers move from vertex to vertex in a graph to capture an invisible fast intruder that may occupy either vertices or edges. Fast searching is a monotonic internal model in which at every move a new edge of the graph G must be guaranteed to be free of the intruder. That is once all searchers are placed the graph G is cleared in exactly vertical bar E(G)vertical bar moves. Such a restriction obviously necessitates a larger number of searchers. We examine this model ...