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Yılmaz, Özgür

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Researcher Of Publications: search.filters.isAuthorOfPublication.99cfdee0-dffe-4993-9bbd-6f40a3d545c7

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Now showing 1 - 10 of 15
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    Stability of an allocation of objects
    (Springer, 2022) Yilmaz, Murat; Department of Economics; Yılmaz, Özgür; Faculty Member; Department of Economics; College of Administrative Sciences and Economics; 108638
    A central stability notion for allocation problems when there are private endowments is core: no coalition should be able to block the allocation. But, for an exchange economy of discrete resources, core can be empty. An alternative stability axiom is the bargaining set a la Aumann and Maschler (Advances in game theory, Annals of mathematics studies, Princeton University Press, Princeton, pp 443-476, 1964): a blocking by a coalition is justified only if there is no counter-objection to it and an allocation is in the bargaining set if there does not exist a justified blocking. Allowing for weak preferences, we prove that any allocation obtained by the well-known Top Trading Cycles class is in the bargaining set, but not all allocations in the bargaining set can be obtained by this class.
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    The strategic advantage of inequality averse preferences
    (Boğaziçi Üniversitesi İktisadi ve İdari Bilimler Fakültesi, 2012) Department of Economics; Yılmaz, Özgür; Faculty Member; Department of Economics; College of Administrative Sciences and Economics; 108638
    It is usually assumed that the sole purpose of agents is to maximize their own material payoff independently from what other agents receive, and that this yields a strategic advantage in terms of receiving a higher payoff compared to other types of players, if any. On the contrary, it is shown that in certain subclasses of games, players with negatively interdependent preferences have an unambiguous strategic advantage over the independent players (Koçkesen et al., 2000). We analyze a different type of interdependency in games; in particular, we analyze games where players with inequality averse preferences have a strategic advantage over the independent players. / Genel olarak, bireylerin iktisadi kararlar alırken, kendi çıkarlarının azami olmasını sağlamaktan başka bir hedeflerinin olmadığı, herhangi bir paylaşımdan aldıkları faydanın da diğer bireylerin elde ettiklerinden bağımsız olduğu ve bu motivasyonun stratejik bir avantaj sağladığı varsayılır. Fakat gösterilmiştir ki, bazı oyun kümelerinde, diğer bireylerin elde ettikleri ile negatif bir bağımlılık içeren tercihler stratejik bir avantaj sağlamaktadır (Koçkesen v.d., 2000). Bu çalışmada, başka türlü bir bağımlılık içeren tercihleri, eşitsizlik karşıtı tercihleri, stratejik avantaj açısından inceliyoruz.
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    Kidney exchange: mechanism design approach and the case of Turkey
    (Bilgesel Yayincilik San and Tic Ltd, 2012) Department of Economics; Yılmaz, Özgür; Faculty Member; Department of Economics; College of Administrative Sciences and Economics; 108638
    Kidney exchange: Mechanism design approach and the case of Turkey the preferred treatment for most of the kidney diseases is transplantation. a kidney patient can receive a transplant either from live donors or from deceased donors. a transplant is possible only if there is no medical incompatibility between the patient and the donor, otherwise the kidney of the donor is not utilized and the patient goes to the waiting list for cadaveric kidneys. Since there are not enough donors, the priority of the transplantation centers is to develop mechanisms in order to avoid such loss of kidney resources. We focus on a particular mechanism, priority mechanism, by analyzing it in the context of kidney exchange in Turkey. We theoretically compare this mechanism under the current system of independent transplantation centers and the system of centralized exchange. We argue that a centralized exchange mechanism increases the welfare of the patients and it is crucial to switch to the centralized system.
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    DRX and QoS-aware energy-efficient uplink scheduling for long term evolution
    (IEEE, 2013) Koç, Ali T.; N/A; Department of Economics; Department of Electrical and Electronics Engineering; Ergül, Özgür; Yılmaz, Özgür; Akan, Özgür Barış; PhD Student; Faculty Member; Faculty Member; Department of Economics; Department of Electrical and Electronics Engineering; Graduate School of Sciences and Engineering; College of Administrative Sciences and Economics; College of Engineering; 156793; 108638; 6647
    Discontinuous reception (DRX) is supported in 3GPP Long Term Evolution (LTE) to reduce power consumption of user equipments (UEs). Power conservation achieved via DRX can be further increased with a packet scheduler that takes DRX states into consideration. Thus, in addition to quality of service (QoS) and fairness factors, which have been the main focus so far in scheduler design, energy efficiency must also be considered in scheduling. In this paper, we introduce a DRX and QoS-aware uplink packet scheduling algorithm (DQEPS) for LTE networks. One of the main reasons of poor DRX utilization is the continuous uplink packet traffic generated by applications working in the background. Accordingly, we first lay out the cumulative distribution functions (CDF) of interpacket arrival durations constructed by inspecting uplink packet transmission for various applications. Then, we form metrics for each bearer using these CDFs along with the DRX states, QoS parameters, channel conditions, and the buffer status of the bearers. Using these metrics, we develop a scheduling algorithm for the uplink, which aims to maximize power conservation of DRX mechanism by scheduling packets in a way that tries to minimize on duration, while meeting the QoS requirements. Performance evaluations indicate that DQEPS reduces power consumption significantly compared to the previously proposed methods for LTE.
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    PublicationOpen Access
    Random assignment under weak preferences
    (Elsevier, 2009) Department of Economics; Yılmaz, Özgür; Faculty Member; Department of Economics; College of Administrative Sciences and Economics; 108638
    The natural preference domain for many practical settings of the assignment problems is the one in which agents are allowed to be indifferent between objects, the weak preference domain. Most of the existing work on assignment problems assumes strict preferences. There are important exceptions. but they provide solutions only to the assignment problems with a social endowment, where agents own objects collectively and there are no private endowments. We consider the general class of assignment problems with private endowments and a social endowment. Our main contribution is a recursive solution for the weak preference domain. Our solution satisfies individual rationality, ordinal efficiency and a recently introduced fairness axiom, no justified-envy.
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    PublicationOpen Access
    Kidney exchange: an egalitarian mechanism
    (Elsevier, 2011) Department of Economics; Yılmaz, Özgür; Faculty Member; Department of Economics; College of Administrative Sciences and Economics; 108638
    Kidney exchange programs utilize both deceased-donor and live-donor kidneys. One of these programs, a two-way kidney paired donation (KPD), involves two patients exchanging their live donors' kidneys. Another possibility is a list exchange (LE): a living incompatible donor provides a kidney to a candidate on the deceased-donor waitlist and in return the intended recipient of this donor receives a priority on the waitlist. By taking into consideration the fact that transplants from live donors have a higher chance of success than those from cadavers, we characterize the set of efficient and egalitarian exchanges involving the KPD's and LE's.
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    PublicationOpen Access
    The probabilistic serial mechanism with private endowments
    (Elsevier, 2010) Department of Economics; Yılmaz, Özgür; Faculty Member; Department of Economics; College of Administrative Sciences and Economics; 108638
    A random assignment is ordinally efficient if it is not stochastically dominated with respect to individual preferences over sure objects. When there are no private endowments, the set of ordinally efficient random assignments is characterized by the eating algorithm (Bogomolnaia and Moulin, 2001). When there are private endowments, the main requirement is individual rationality; however, the eating algorithm fails to deliver this property. Our contribution is the natural generalization of the eating algorithm for this general class of problems. The family of this generalized eating algorithm characterizes the set of individually rational and ordinally efficient random assignments. A special solution in this family, the individually rational probabilistic serial (PS(IR)), also achieves a new fairness axiom, no justified-envy. However, it is not immune to strategic manipulation. We show that individual rationality, no justified-envy and strategy-proofness are incompatible.
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    PublicationOpen Access
    DRX and QoS-aware energy-efficient uplink scheduling for long term evolution
    (Institute of Electrical and Electronics Engineers (IEEE), 2013) Koç, Ali T.; Ergül, Özgür; Yılmaz, Özgür; Akan, Özgür Barış; PhD Student; Faculty Member; Faculty Member; College of Engineering; N/A; 108638; N/A
    Discontinuous reception (DRX) is supported in 3GPP Long Term Evolution (LTE) to reduce power consumption of user equipments (UEs). Power conservation achieved via DRX can be further increased with a packet scheduler that takes DRX states into consideration. Thus, in addition to quality of service (QoS) and fairness factors, which have been the main focus so far in scheduler design, energy efficiency must also be considered in scheduling. In this paper, we introduce a DRX and QoS-aware uplink packet scheduling algorithm (DQEPS) for LTE networks. One of the main reasons of poor DRX utilization is the continuous uplink packet traffic generated by applications working in the background. Accordingly, we first lay out the cumulative distribution functions (CDF) of interpacket arrival durations constructed by inspecting uplink packet transmission for various applications. Then, we form metrics for each bearer using these CDFs along with the DRX states, QoS parameters, channel conditions, and the buffer status of the bearers. Using these metrics, we develop a scheduling algorithm for the uplink, which aims to maximize power conservation of DRX mechanism by scheduling packets in a way that tries to minimize ON duration, while meeting the QoS requirements. Performance evaluations indicate that DQEPS reduces power consumption significantly compared to the previously proposed methods for LTE.
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    PublicationOpen Access
    Utility representation of lower separable preferences
    (Elsevier, 2008) Department of Economics; Yılmaz, Özgür; Faculty Member; Department of Economics; College of Administrative Sciences and Economics; 108638
    Topological separability is crucial for the utility representation of a complete preference relation. When preferences are incomplete, this axiom has Suitably defined Counterparts: Upper separability and lower separability [Ok, E.A., 2002. Utility representation of an incomplete preference relation. Journal of Economic Theory 104, 429-449]. We consider the problem of representing an incomplete preference relation by means of a vector-valued utility function; we obtain representation results under the lower separability assumption. Our results extend the main representation theorems by Ok [Ok, E.A., 2002. Utility representation of an incomplete preference relation. journal of Economic Theory 104, 429-449] in terms of the separability axioms.
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    PublicationOpen Access
    A characterization of the extended serial correspondence
    (Elsevier, 2015) Heo, Eun Jeong; Department of Economics; Yılmaz, Özgür; Faculty Member; Department of Economics; College of Administrative Sciences and Economics; 108638
    We study the problem of assigning objects to a group of agents. We focus on probabilistic methods that take agents' ordinal preferences over the objects. Importantly, we allow for indifferences among objects. Katta and Sethuraman (2006) propose the extended serial correspondence to solve this problem. Our main result is a characterization of the extended serial correspondence in welfare terms by means of stochastic dominance efficiency, stochastic dominance no-envy and "limited invariance," a requirement we adapt from Heo (2014a). We also prove that an assignment matrix is selected by the extended serial correspondence if and only if it satisfies "non-wastefulness" and "ordinal fairness," which we adapt from Kesten et al.