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Publication Metadata only A Bilevel p-median model for the planning and protection of critical facilities(Springer, 2013) Aras, Necati; Piyade, Nuray; Department of Business Administration; Aksen, Deniz; Faculty Member; Department of Business Administration; College of Administrative Sciences and Economics; 40308The bilevel p-median problem for the planning and protection of critical facilities involves a static Stackelberg game between a system planner (defender) and a potential attacker. The system planner determines firstly where to open p critical service facilities, and secondly which of them to protect with a limited protection budget. Following this twofold action, the attacker decides which facilities to interdict simultaneously, where the maximum number of interdictions is fixed. Partial protection or interdiction of a facility is not possible. Both the defender's and the attacker's actions have deterministic outcome; i.e., once protected, a facility becomes completely immune to interdiction, and an attack on an unprotected facility destroys it beyond repair. Moreover, the attacker has perfect information about the location and protection status of facilities; hence he would never attack a protected facility. We formulate a bilevel integer program (BIP) for this problem, in which the defender takes on the leader's role and the attacker acts as the follower. We propose and compare three different methods to solve the BIP. The first method is an optimal exhaustive search algorithm with exponential time complexity. The second one is a two-phase tabu search heuristic developed to overcome the first method's impracticality on large-sized problem instances. Finally, the third one is a sequential solution method in which the defender's location and protection decisions are separated. The efficiency of these three methods is extensively tested on 75 randomly generated instances each with two budget levels. The results show that protection budget plays a significant role in maintaining the service accessibility of critical facilities in the worst-case interdiction scenario.Publication Metadata only A bourdieuan relational perspective for entrepreneurship research(Wiley, 2014) Tatli, Ahu; Vassilopoulou, Joana; Forson, Cynthia; Slutskaya, Natasha; Department of Business Administration; Özbilgin, Mustafa; Other; Department of Business Administration; College of Administrative Sciences and Economics; N/AIn this paper, we illustrate the possibilities a relational perspective offers for overcoming the dominant dichotomies (e.g., qualitative versus quantitative, agency versus structure) that exist in the study of entrepreneurial phenomena. Relational perspective is an approach to research that allows the exploration of a phenomenon, such as entrepreneurship, as irreducibly interconnected sets of relationships. We demonstrate how Pierre Bourdieu's concepts may be mobilized to offer an exemplary toolkit for a relational perspective in entrepreneurship research.Publication Metadata only A construal level account of the impact of religion and god on prosociality(Sage, 2020) N/A; N/A; Department of Business Administration; Canlı, Zeynep Gürhan; Karataş, Mustafa; PhD Student; Faculty Member; Department of Business Administration; Graduate School of Business; College of Administrative Sciences and Economics; N/A; 16135This research shows that the two most prevalent religious constructs-God and religion-differentially impact cognition. Activating thoughts about God (vs. religion) induces a relatively more abstract (vs. concrete) mindset (Studies 1a-1c). Consequently, time donation intentions (Study 2) and actual monetary donations (Study 3) after a God (vs. religion) prime increase when people are presented an abstractly (vs. concretely) framed donation appeal. Similarly, people donate more money to distant (vs. close) donation targets, which are construed relatively abstractly (vs. concretely), when a religious speech activates predominantly God-specific (vs. religion-specific) thoughts (Study 4). These effects are mediated by "feeling right" under construal level fit (Study 3). Overall, this research significantly advances extant knowledge on religious cognition and past research on the link between religion and prosociality.Publication Metadata only A dynamic analysis of market entry rates in a global industry: a community ecology perspective(Emerald, 1999) Çavuşgil, S. Tamer; Department of Business Administration; Tunalı, Ayşegül Özsomer; Faculty Member; Department of Business Administration; College of Administrative Sciences and Economics; 108158States that it is critical that incumbent firms understand the processes that enhance or inhibit entry of new firms into their industry. A new entrant into an industry may create additional demand by legitimizing the technology/products, and/or may share the existing market by drawing buyers away from incumbents. An analysis of market entry rates is especially important in new, high technology industries where sub‐groups of firms pursue different technology and global market diversification strategies because such sub‐groups may have asymmetrical cross‐effects on entry rates of new firms. Suggests a community ecology approach to assessing the impact of industry density on new firm entry rates. The framework is demonstrated by applying it to the global personal computer industry during the period of 1977‐1992. Results suggest that density has a nonmonotonic positive effect, while the firm‐level variables of technological strategy and market expansion strategies have a monotonic positive effect on new firm entry rates.Publication Metadata only A mixed integer programming formulation for the 1-maximin problem(Operational Research Society, 2000) N/A; Department of Business Administration; Sayın, Serpil; Faculty Member; Department of Business Administration; College of Administrative Sciences and Economics; 6755In this paper, I present a mixed integer programming (MIP) formulation for the 1-maximin problem with rectilinear distance. The problem mainly appears in facility location while trying to locate an undesirable facility. The rectilinear distance is quite commonly used in the location literature. Our numerical experiments show that one can solve reasonably large location problems using a standard MIP solver. We also provide a linear programming formulation that helps find an upper bound on the objective function value of the 1-maximin problem with any norm when extreme points of the feasible region are known. We discuss various extension alternatives for the MIP formulation.Publication Open Access A multiperiod stochastic production planning and sourcing problem with service level constraints(Springer, 2005) Yıldırım, Işıl; Department of Business Administration; Department of Industrial Engineering; Tan, Barış; Karaesmen, Fikri; Faculty Member; Faculty Member; Department of Business Administration; Department of Industrial Engineering; College of Administrative Sciences and Economics; College of Engineering; 28600; 3579We study a stochastic multiperiod production planning and sourcing problem of a manufacturer with a number of plants and/or subcontractors. Each source, i.e. each plant and subcontractor, has a different production cost, capacity, and lead time. The manufacturer has to meet the demand for different products according to the service level requirements set by its customers. The demand for each product in each period is random. We present a methodology that a manufacturer can utilize to make its production and sourcing decisions, i.e., to decide how much to produce, when to produce, where to produce, how much inventory to carry, etc. This methodology is based on a mathematical programming approach. The randomness in demand and related probabilistic service level constraints are integrated in a deterministic mathematical program by adding a number of additional linear constraints. Using a rolling horizon approach that solves the deterministic equivalent problem based on the available data at each time period yields an approximate solution to the original dynamic problem. We show that this approach yields the same result as the base stock policy for a single plant with stationary demand. For a system with dual sources, we show that the results obtained from solving the deterministic equivalent model on a rolling horizon gives similar results to a threshold subcontracting policy.Publication Open Access A preference-based, multi-unit auction for pricing and capacity allocation(Elsevier, 2018) Lessan, Javad; Department of Business Administration; Karabatı, Selçuk; Faculty Member; Department of Business Administration; College of Administrative Sciences and Economics; 38819We study a pricing and allocation problem of a seller of multiple units of a homogeneous item, and present a semi-market mechanism in the form of an iterative ascending-bid auction. The auction elicits buyers' preferences over a set of options offered by the seller, and processes them with a random-priority assignment scheme to address buyers' "fairness" expectations. The auction's termination criterion is derived from a mixed-integer programming formulation of the preference-based capacity allocation problem. We show that the random priority- and preference-based assignment policy is a universally truthful mechanism which can also achieve a Pareto-efficient Nash equilibrium. Computational results demonstrate that the auction mechanism can extract a substantial portion of the centralized system's profit, indicating its effectiveness for a seller who needs to operate under the "fairness" constraint.Publication Metadata only A procedure to find discrete representations of the efficient set with specified coverage errors(Inst Operations Research Management Sciences, 2003) Department of Business Administration; Sayın, Serpil; Faculty Member; Department of Business Administration; College of Administrative Sciences and Economics; 6755An important issue in multiple objective mathematical programming is finding discrete representations of the efficient set. Because discrete points can be directly studied by a decision maker, a discrete representation can serve as the solution to the multiple objective problem at hand. However, the discrete representation must be of acceptable quality to ensure that a most-preferred solution identified by a decision maker is of acceptable quality. Recently, attributes for measuring the quality of discrete representations have been proposed. Although discrete representations can be obtained in many different ways, and their quality evaluated afterwards, the ultimate goal should be to find such representations so as to conform to specified quality standards. We present a method that can find discrete representations of the efficient set according to a specified level of quality. The procedure is based on mathematical programming tools and can be implemented relatively easily when the domain of interest is a polyhedron. The nonconvexity of the efficient set is dealt with through a coordinated decomposition approach. We conduct computational experiments and report results.Publication Open Access A threat to loyalty: fear of missing out (FOMO) leads to reluctance to repeat current experiences(Public Library of Science, 2020) Hayran, Ceren; Anık, Lalin; Department of Business Administration; Canlı, Zeynep Gürhan; Faculty Member; Department of Business Administration; Graduate School of Business; 16135We investigate a popular but underresearched concept, the fear of missing out (FOMO), on desirable experiences of which an individual is aware, but in which they do not partake. Through laboratory and field studies, we establish FOMO's pervasiveness as a psychological phenomenon, present real-life contexts wherein FOMO may be experienced, and explore its behavioral consequences. Specifically, we show that FOMO poses a threat to loyalty by decreasing one's intentions to repeat a current experience and may decrease the valuation of the current experience.Publication Open Access A trilevel r-interdiction selective multi-depot vehicle routing problem with depot protection(Elsevier, 2020) Hesam Sadati, Mir Ehsan; Aras, Necati; Department of Business Administration; Aksen, Deniz; Faculty Member; Department of Business Administration; College of Administrative Sciences and Economics; 40308The determination of critical facilities in supply chain networks has been attracting the interest of the Operations Research community. Critical facilities refer to structures including bridges, railways, train/metro stations, medical facilities, roads, warehouses, and power stations among others, which are vital to the functioning of the network. In this study we address a trilevel optimization problem for the protection of depots of utmost importance in a routing network against an intelligent adversary. We formulate the problem as a defender-attacker-defender game and refer to it as the trilevel r-interdiction selective multi-depot vehicle routing problem (3LRI-SMDVRP). The defender is the decision maker in the upper level problem (ULP) who picks u depots to protect among m existing ones. In the middle level problem (MLP), the attacker destroys r depots among the (m–u) unprotected ones to bring about the biggest disruption. Finally, in the lower level problem (LLP), the decision maker is again the defender who optimizes the vehicle routes and thereby selects which customers to visit and serve in the wake of the attack. All three levels have an identical objective function which is comprised of three components. (i) Operating or acquisition cost of the vehicles. (ii) Traveling cost incurred by the vehicles. (iii) Outsourcing cost due to unvisited customers. The defender aspires to minimize this objective function while the attacker tries to maximize it. As a solution approach to this trilevel discrete optimization problem, we resort to a smart exhaustive enumeration in the ULP and MLP. For the LLP we design a metaheuristic algorithm that hybridizes Variable Neighborhood Descent and Tabu Search techniques adapted to the Selective MDVRP (SMDVRP). The performance of this algorithm is demonstrated on 33 MDVRP benchmark instances existing in the literature and 41 SMDVRP instances generated from them. Numerical experiments on a large number of 3LRI-SMDVRP instances attest that our comprehensive method is effective in dealing with the defender-attacker-defender game on multi-depot routing networks.