@article {1499, title = {Mind the independence gap}, journal = {Discrete Mathematics}, volume = {343}, year = {2020}, pages = {111943}, abstract = {

The independence gap of a graph was introduced by Ekim et al.\ in 2018 as a measure of how far a graph is from being well-covered. It is defined as the difference between the maximum and minimum size of a maximal independent set. We investigate the independence gap of a graph from structural and algorithmic points of view, with a focus on classes of perfect graphs. Generalizing results on well-covered graphs due to Dean and Zito (1994) and Hujdurovi{\'c} et al.\ (2018), we express the independence gap of a perfect graph in terms of clique partitions and use this characterization to develop a polynomial-time algorithm for recognizing graphs of constant independence gap in any class of perfect graphs of bounded clique number. Next, we introduce a hereditary variant of the parameter, which we call hereditary independence gap and which measures the maximum independence gap over all induced subgraphs of the graph. We show that determining whether a given graph has hereditary independence gap at most k is polynomial-time solvable if k is fixed and co-NP-complete if k is part of input. We also investigate the complexity of the independent set and independent domination problems in graph classes related to independence gap. In particular, we show that the two problems are NP-complete in the class of graphs of independence gap at most one and that the weighted independent set problem is polynomial-time solvable in any class of graphs with bounded hereditary independence gap. Combined with some known results on claw-free graphs, our results imply that the independent domination problem is solvable in polynomial time in the class of {claw, 2P3}-free graphs.

}, keywords = {Hereditary independence gap, Independent dominating set, Maximal independent set, NP-hard problem, Polynomial-time algorithm, Well-covered graph}, issn = {0012-365X}, doi = {https://doi.org/10.1016/j.disc.2020.111943}, url = {https://www.sciencedirect.com/science/article/pii/S0012365X20301321}, author = {Ekim, Tinaz and Didem G{\"o}z{\"u}pek and Ademir Hujdurovi{\'c} and Martin Milani{\v c}} } @article {1503, title = {On Almost Well-Covered Graphs of Girth at Least 6}, journal = {Discrete Mathematics \& Theoretical Computer Science}, volume = {20}, year = {2018}, author = {Milani{\v c}, Martin and Hujdurovi{\'c}, Ademir and G{\"o}z{\"u}pek, Didem and Ekim, Tinaz} } @article {1474, title = {Impacts of Regulatory Transformation Processes to the Downstream Oil Market in Turkey}, journal = {International Journal of Energy Economics and Policy}, volume = {8}, year = {2018}, pages = {141{\textendash}149}, issn = {2146-4553}, author = {Metin, Erol and G{\"u}rkan Kumbaro{\u g}lu} } @article {1160, title = {Accelerating Transition Dynamics in City Regions: A Qualitative Modeling Perspective}, journal = {Sustainability}, volume = {9}, year = {2017}, pages = {1254}, author = {Valkering, Pieter and G{\"o}nen{\c c} Y{\"u}cel and Gebetsroither-Geringer, Ernst and Markvica, Karin and Meynaerts, Erika and Frantzeskaki, Niki} } @article {1494, title = {Effect of Lead Time on Anchor-and-Adjust Ordering Policy in Continuous Time Stock Control Systems}, journal = {Korean System Dynamics Review}, volume = {2}, year = {2017}, month = {Jun}, pages = {65{\textendash}85}, author = {Mutallip, Ahmet and Yasarcan, Hakan} } @article {1508, title = {On matching extendability of lexicographic products}, journal = {RAIRO-Oper. Res.}, volume = {51}, year = {2017}, pages = {857-873}, doi = {10.1051/ro/2016072}, url = {https://doi.org/10.1051/ro/2016072}, author = {Chiarelli, Nina and Dibek, Cemil and Ekim, Tinaz and G{\"o}z{\"u}pek, Didem and Miklavic, Stefko} } @article {1189, title = {The Shifting the Burden Archetype: A Workforce and Task Backlog Management Game}, journal = {Korean System Dynamics Review}, volume = {18}, year = {2017}, pages = {81-110}, author = {A. Mutallip and Hakan Ya{\c s}arcan} } @conference {mutallip2014desired, title = {Desired Supply Line Value Calculation for Multi-Supplier Systems}, booktitle = {The 32nd International System Dynamics Conference, Delft, Netherlands}, year = {2014}, publisher = {System Dynamics Society (http://www.systemdynamics.org/conferences/2014/index.html)}, organization = {System Dynamics Society (http://www.systemdynamics.org/conferences/2014/index.html)}, author = {Mutallip, Ahmet and Yasarcan, Hakan} } @article {ekim2014polar, title = {Polar cographs}, journal = {Discrete Applied Mathematics}, volume = {171}, number = {EPFL-ARTICLE-199582}, year = {2014}, pages = {158{\textendash}158}, publisher = {Elsevier Science Bv}, author = {Ekim, Tinaz and Mahadev, NVR and de Werra, Dominique} } @inbook {Yucel2013a, title = {The actor-option framework: a general framework for modelling socio-technical systems in transitions}, booktitle = {Infranomics: Sustainability, Engineering Design and Governance}, series = {Topics in Safety, Risk, Reliability and Quality}, volume = {24}, year = {2013}, pages = {407{\textendash}418}, publisher = {Springer International Publishing}, organization = {Springer International Publishing}, address = {Cham}, keywords = {modelling, simulation, socio-technical transitions}, isbn = {978-3-319-02492-9}, doi = {10.1007/978-3-319-02493-6}, url = {http://link.springer.com/10.1007/978-3-319-02493-6}, author = {G{\"o}nen{\c c} Y{\"u}cel}, editor = {Gheorghe, Adrian V. and Masera, Marcelo and Katina, Polinpapilinho F.} } @article {ekim2013polar, title = {Polar permutation graphs are polynomial-time recognisable}, journal = {European Journal of Combinatorics}, volume = {34}, number = {3}, year = {2013}, pages = {576{\textendash}592}, publisher = {Academic Press}, author = {Ekim, Tinaz and Heggernes, Pinar and Meister, Daniel} } @inbook {ekim2012computing, title = {Computing minimum geodetic sets of proper interval graphs}, booktitle = {LATIN 2012: Theoretical Informatics}, year = {2012}, pages = {279{\textendash}290}, publisher = {Springer Berlin Heidelberg}, organization = {Springer Berlin Heidelberg}, author = {Ekim, Tinaz and Erey, Aysel and Heggernes, Pinar and van{\textquoteright}t Hof, Pim and Meister, Daniel} } @article {1477, title = {Evaluation of economically optimal retrofit investment options for energy savings in buildings}, journal = {Energy and Buildings}, volume = {49}, year = {2012}, pages = {327-334}, abstract = {

In this study, a techno-economic evaluation method for the energy retrofit of buildings is introduced, geared toward finding the economically optimal set of retrofit measures. Split incentives of building owners and users are considered explicitly in a conventional (static) evaluation to identify the investment alternatives maximizing the net present value (NPV). Energy price uncertainty for various distributional assumptions of the stochastic variables is addressed through Monte Carlo simulation. Results from the simulation are used to compute probabilities and expected NPVs. Based on this, a sequential (dynamic) evaluation method is developed, featuring a real options investment appraisal. The real options approach is introduced as an advancement in the practice of economic evaluation of building retrofit investment options. The new method is applied to an office building in Germany, illustrating its performance. The case study results indicate that energy price changes significantly affect the profitability of retrofit investments, and that high price volatility creates a substantial value of waiting, making it more rational to postpone the investment.

}, keywords = {Building energy efficiency, Energy conservation, Net present value, Real options}, issn = {0378-7788}, doi = {https://doi.org/10.1016/j.enbuild.2012.02.022}, url = {https://www.sciencedirect.com/science/article/pii/S0378778812000990}, author = {G{\"u}rkan Kumbaro{\u g}lu and Reinhard Madlener} } @conference {mutallip2012parametric, title = {A Parametric Analysis of the Effect of a Material Supply Line Delay in Stock Management}, booktitle = {The 30th International System Dynamics Conference, St. Gallen, Switzerland}, year = {2012}, publisher = {System Dynamics Society (http://www.systemdynamics.org/conferences/2012/index.html)}, organization = {System Dynamics Society (http://www.systemdynamics.org/conferences/2012/index.html)}, author = {Mutallip, Ahmet and Yasarcan, Hakan} } @article {34, title = {Toward Development of Adaptive Service-Based Software Systems}, journal = {IEEE Transactions on Services Computing}, volume = {2}, year = {2009}, pages = {247-260}, abstract = {

The rapid adoption of service-oriented architecture (SOA) in many large-scale distributed applications requires the development of adaptive service-based software systems (ASBS) with the capability of monitoring the changing system status, analyzing, and controlling tradeoffs among various quality-of-service (QoS) aspects, and adapting service configurations to satisfy multiple QoS requirements simultaneously. In this paper, our results toward the development of adaptive service-based software systems are presented. The formulation of activity-state-QoS (ASQ) models and how to use the data from controlled experiments to establish ASQ models for capturing the cause-effect dynamics among service activities, system resource states, and QoS in service-based systems are presented. Then, QoS monitoring modules based on ASQ models and SOA-compliant simulation models are developed to support the validation of the ASBS design. The main idea for developing QoS adaptation modules based on ASQ models is discussed. An experiment based on a voice communication service is used to illustrate our results.

}, keywords = {Design concepts, distributed/Internet-based software engineering tools and techniques, methodologies, modeling methodologies, quality of services, services systems}, issn = {1939-1374}, doi = {http://doi.ieeecomputersociety.org/10.1109/TSC.2009.17}, author = {Stephen S. Yau and Nong Ye and Hessam S. Sarjoughian and Dazhi Huang and Auttawut Roontiva and Mustafa Gokce Baydogan and Mohammed A. Muqsith} } @article {ekim2008polar, title = {Polar cographs}, journal = {Discrete Applied Mathematics}, volume = {156}, number = {10}, year = {2008}, pages = {1652{\textendash}1660}, publisher = {North-Holland}, author = {Ekim, Tinaz and Mahadev, Nadimpalli VR and de Werra, Dominique} } @article {1481, title = {A real options evaluation model for the diffusion prospects of new renewable power generation technologies}, journal = {Energy Economics}, volume = {30}, year = {2008}, pages = {1882-1908}, abstract = {

This study presents a policy planning model that integrates learning curve information on renewable power generation technologies into a dynamic programming formulation featuring real options analysis. The model recursively evaluates a set of investment alternatives on a year-by-year basis, thereby taking into account that the flexibility to delay an irreversible investment expenditure can profoundly affect the diffusion prospects of renewable power generation technologies. Price uncertainty is introduced through stochastic processes for the average wholesale price of electricity and for input fuel prices. Demand for electricity is assumed to be increasingly price-sensitive, as the electricity market deregulation proceeds, reflecting new options of consumers to react to electricity price changes (such as time-of-use pricing, unbundled electricity services, and choice of supplier). The empirical analysis is based on data for the Turkish electricity supply industry. Apart from general implications for policy-making, it provides some interesting insights about the impact of uncertainty and technical change on the diffusion of various emerging renewable energy technologies.

}, keywords = {Dynamic programming, Investment planning, Learning curve, Real options, Renewable energy technology diffusion, Turkey}, issn = {0140-9883}, doi = {https://doi.org/10.1016/j.eneco.2006.10.009}, url = {https://www.sciencedirect.com/science/article/pii/S0140988306001241}, author = {G{\"u}rkan Kumbaro{\u g}lu and Reinhard Madlener and Mustafa Demirel} } @article {Yucel2008, title = {Studying transition dynamics via focusing on underlying feedback interactions}, journal = {Computational and Mathematical Organization Theory}, volume = {14}, number = {4}, year = {2008}, pages = {320{\textendash}349}, issn = {1381-298X}, doi = {10.1007/s10588-008-9032-4}, url = {http://www.springerlink.com/index/10.1007/s10588-008-9032-4}, author = {G{\"o}nen{\c c} Y{\"u}cel and Chiong Meza, Catherine Miluska} } @article {MenEtAl2007, title = {An Exact Approach to Direct Aperture Optimization in IMRT Treatment Planning}, journal = {Physics in Medicine and Biology}, volume = {52}, number = {24}, year = {2007}, pages = {7333-7352}, doi = {http://dx.doi.org/10.1088/0031-9155/52/24/009}, author = {Chunhua Men and H. Edwin Romeijn and Z C Ta{\c s}k{\i}n and James F. Dempsey} } @article {1482, title = {Modeling Technology Adoption as an Irreversible Investment under Uncertainty the Case of the Turkish Electricity Supply Industry}, journal = {Energy Economics}, volume = {27}, year = {2005}, month = {Jan}, pages = {139{\textendash}163}, author = {Madlener, Reinhard and G{\"u}rkan Kumbaro{\u g}lu and ED{\.I}GER, {\c S}EVKET VOLKAN} } @article {1484, title = {Energy and Climate Policy Analysis with the Hybrid Bottom Up Computable General Equilibrium Model SCREEN The Case of the Swiss CO2 Act}, journal = {Annals of Operations Research}, volume = {121}, year = {2003}, month = {Jul}, pages = {181{\textendash}203}, author = {G{\"u}rkan Kumbaro{\u g}lu and Madlener, Reinhard} }