Short Paper - A Note on Robust Combinatorial Optimization with Generalized Interval Uncertainty

In this paper, we consider a robust combinatorial optimization problem with uncertain weights and propose an uncertainty set that generalizes interval uncertainty by imposing lower and upper bounds on deviations of subsets of items. We prove that if the number of such subsets is fixed and the family of these subsets is laminar, then the robust combinatorial optimization problem can be solved by solving a fixed number of nominal problems. This result generalizes a previous similar result for the case where the family of these subsets is a partition of the set of items

Public support for European Union membership in Turkey between 2005-2014

Within the discussion of EU relations of Turkey, it is clear that until recent the importance of public opinion and its formation have been neglected from related research. Although the existent research deals with individual level factors shaping public opinion, this thesis proposes an alternative approach that public opinion formation is highly related to political cues that are provided from certain government institutions and political elite, among other determinants of national economic growth, tendency to trust in the national government and parliament. The decline in public support in Turkey regarding EU membership has been analyzed and tendencies within the period of 2005-2014 are presented in order to provide explanations to the association of the public opinion formation to the related propositions. In order to observe the relation of external and internal factors regarding policy formation of the political elite, the historical background of Turkish membership project to EU has been touched upon, and related political discourses have been analyzed to correlate public opinion formation to elite messages in the respective period. In doing this, the thesis aims to contribute to public opinion analyses of Turkey regarding EU membership process, while embracing Eurobarometer public opinion surveys from 2005 to 2014

Essays on some combinatorial optimization problems with interval data

Ankara : The Department of Industrial Engineering and the Institute of Engineering and Sciences of Bilkent Univ., 1999.Thesis (Master's) -- Bilkent University, 1999.Includes bibliographical references leaves 84-85In this study, we investigate three well-known problems, the longest path problem on directed acyclic graphs, the minimum spanning tree problem and the single machine scheduling problem with total flow time criterion, where the input data for all problems are given as interval numbers. Since optimal solutions depend on the realization of the data, we define new optimality concepts to aid decision making. VVe present characterizations for these “optimal” solutions and suggest polynomial time algorithms to find them in some special cases.Yaman, HandeM.S

Formulations and valid inequalities for the capacitated dispersion problem

This work focuses on the capacitated dispersion problem for which we study several mathematical formulations in different spaces using variables associated with nodes, edges, and costs. The relationships among the presented formulations are investigated by comparing the projections of the feasible sets of the LP relaxations onto the subspace of natural variables. These formulations are then strengthened with families of valid inequalities and variable-fixing procedures. The separation problems associated with the valid inequalities that are exponential in number are shown to be polynomially solvable by reducing them to longest path problems in acyclic graphs. The dual bounds obtained from stronger but larger formulations are used to improve the strength of weaker but smaller formulations. Several sets of computational experiments are conducted to illustrate the usefulness of the findings, as well as the aptness of the formulations for different types of instances

The Effect of Mixture Parameters on the Surface Properties of Roller Compacted Concrete (RCC) Pavements

In Turkey, the use of RCC pavements is increasing in urban and rural roads. However, a detailed study examining the effect of RCC mixture parameters on the pavement surface properties that affect road driving comfort and safety is not available in literature. In this study, in order to cover that gap in literature 12 RCC mixtures prepared with different cement dosages, aggregate gradations and water amounts were compacted by "Superpave-Gyratory-Compactor" at different levels. Later, the surface characteristics were evaluated with British pendulum and sand patch tests. It was concluded that cement dosage, water content and gradation have an effect not only in terms of strength but also in terms of pavement surface properties, and recommendations were made for RCC mixture optimization.Ülkemizde SSB kaplamaların şehir içi ve köy yollarında kullanımı gittikçe artmaktadır. Fakat yol sürüş konforunu ve güvenliğini etkileyen kaplama yüzey özelliklerine, karışım parametrelerinin etkisini inceleyen detaylı bir çalışma uluslararası literatürde mevcut değildir. Bu eksikliği gidermeye yönelik yapılan bu çalışmada, farklı çimento dozajları, agrega gradasyonları ve su oranları ile hazırlanan 12 SSB karışımı, “Superpave-Yoğurmalı-Presi” ile farklı seviyelerde sıkıştırılıp yüzey özellikleri, İngiliz pandülü ve kum yama testleriyle değerlendirilmiştir. Yapılan istatistiksel analizlerde, yoğurma sayısının etkisi görülmezken; SSB çimento dozajı, su muhtevası ve gradasyonun yalnızca mukavemet yönünden değil aynı zamanda yüzey özellikleri bakımından da etkili olduğu sonucuna varılmış ve SSB karışım optimizasyonu için öneriler getirilmiştir

Survivability in hierarchical telecommunications networks

Abstract We consider the problem of designing a two level telecommunications network at minimum cost. The decisions involved are the locations of concentrators, the assignments of user nodes to concentrators and the installation of links connecting concentrators in a reliable backbone network. We define a reliable backbone network as one where there exist at least 2-edge disjoint paths between any pair of concentrator nodes. We formulate this problem as an integer program and propose a facial study of the associated polytope. We describe valid inequalities and give sufficient conditions for these inequalities to be facet defining. We also propose some reduction operations in order to speed up the separation procedures for these inequalities. Using these results, we devise a branch-and-cut algorithm and present some computational results

The initial part of polymorphic ventricular tachycardia as a clue for the sustainability of tachycardia and ablation success: A varying degree of purkinje–Myocardial complicity?

The cardiac Purkinje system is capable of very rapid burst activity suggestive of its potential role in being a driver of polymorphic ventricular tachycardia (VT) (PMVT) or ventricular fibrillation (VF). It plays a pivotal role, however, not only in the triggering of but also the perpetuation of ventricular arrhythmias. A varying degree of Purkinje–myocardial complicity has been blamed in determining not only the sustained or non-sustained nature of PMVT but also the pleomorphism of the non-sustained runs. The initial part of PMVT before cascading to the whole ventricle to establish disorganized VF can give important clues for ablation of PMVT and VF. We present a case of an electrical storm after acute myocardial infarction that was successfully ablated after identifying Purkinje potentials that triggered polymorphic, monomorphic, and pleiomorphic VTs and VF