Publications with Fulltext
Permanent URI for this collectionhttps://hdl.handle.net/20.500.14288/6
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Publication Open Access An empirical investigation of four well-known polynomial-size VRP formulations(NA, 2018) Öncan, Temel; Department of Business Administration; N/A; Aksen, Deniz; Sadatizamanabad, Mirehsan Hesam; Faculty Member; Department of Business Administration; College of Administrative Sciences and Economics; Graduate School of Sciences and Engineering; 40308; N/AThis study presents an in-depth computational analysis of four well-known Capacitated Vehicle Routing Problem (CVRP) formulations with polynomial number of subtour elimination constraints: a node-based formulation and three arc-based (single, two- and multi-commodity flow) formulations. For each formulation, several valid inequalities (VIs) are added for the purpose of tightening the formulation. Moreover, a simple topology-driven granulation scheme is proposed to reduce the number of a certain type of VIs. The lower and upper bounding performance and the solution efficiency of the formulations and respective VI configurations are benchmarked with state-of-the-art commercial optimization software. The extensive computational analysis embraces 121 instances with up to 100 customer nodes. We believe that our findings could be useful for practitioners as well as researchers developing algorithms for the CVRP.Publication Open Access How does self-concept clarity influence happiness in social settings? The role of strangers versus friends(Taylor _ Francis, 2018) Merdin-Uygur, Ezgi; Sarıal-Abi, Gülen; Hesapçı, Özlem; Department of Business Administration; Canlı, Zeynep Gürhan; Faculty Member; Department of Business Administration; College of Administrative Sciences and Economics; 16135Self-concept clarity (SCC), defined as the extent to which the content of an individual’s self-beliefs is clearly and confidently defined and internally consistent, influences experiences in social relationships. This paper extends the previous literature on SCC by proposing and demonstrating that high-SCC individuals anticipate and experience more happiness than low-SCC individuals when they share a social setting with friends and anticipate and experience less happiness than low-SCC individuals when they share a social setting with strangers and that this is because of perceived interpersonal distance. A series of four studies, including both online studies and a field study, support these predictions. Alternative explanations of self-esteem and self-efficacy are also ruled out. The findings yield both theoretical contributions and practical implications.Publication Open Access Purchasing, production, and sales strategies for a production system with limited capacity, fluctuating sales and purchasing prices(Taylor _ Francis, 2019) N/A; Department of Business Administration; Karabağ, Oktay; Tan, Barış; Resercher; Faculty Member; Department of Business Administration; Graduate School of Sciences and Engineering; College of Administrative Sciences and Economics; N/A; 28600In many industries, the revenue and cost structures of manufacturers are directly affected by the volatility of purchasing and sales prices in the markets. We analyze the purchasing, production, and sales policies for a continuous-review discrete material flow production/inventory system with fluctuating and correlated purchasing and sales prices, exponentially distributed raw material and demand inter-arrival times, and processing time. The sales and purchasing prices are driven by the random environmental changes that evolve according to a discrete state space continuous-time Markov process. We model the system as an infinite-horizon Markov decision process under the average reward criterion and prove that the optimal purchasing, production, and sales strategies are state-dependent threshold policies. We propose a linear programming formulation to compute the optimal threshold levels. We examine the effects of the sales price variation, purchasing price variation, correlation between sales and purchasing prices, customer arrival rate and limited inventory capacities on the system performance measures, through a range of numerical experiments. We also examine under which circumstances the use of the optimal policy notably improves the system profit compared to the use of the buy low and sell high naive policy. We show that using the optimal purchasing, production, and sales policies allow manufacturers to improve their profits when the purchasing and sales prices fluctuate.Publication Open Access Partisan and apportionment bias in creating a predominant party system(Elsevier, 2019) Department of International Relations; Department of Business Administration; Çarkoğlu, Ali; Aksen, Deniz; Faculty Member; Faculty Member; Department of International Relations; Department of Business Administration; College of Administrative Sciences and Economics; 125588; 40308Moving beyond the analytical characteristics of apportionment methods or election systems, this article focuses on their outcomes in practice. We illustrate how apportionment and partisan biases working with a high threshold created an electoral environment conducive to the establishment of a predominant party system. We use the historical example of the Turkish experience. We trace the historical development of disproportionality for the entire multi-party elections for the 1950-2015 period. Focusing on the five most recent elections of this period since 2002, we demonstrate how the biases introduced by the apportionment method in use and the 10% threshold have advantaged the leading Justice and Development Party (Adalet ye Kalkinma Partisi, AKP). Our study suggests that a partisan bias favoring AKP still continues to exist at a lower level even after correcting the apportionment and the threshold biases. We underline how these biases form the foundation for a conservative over-representation and emphasize the path-dependent dynamics that keep challengers to the AKP away from the electoral scene, effectively helping to continue its hegemonic position in the system.Publication Open Access Modelling and analysis of a network organization for cooperation of manufacturers on production capacity(Hindawi, 2006) Department of Business Administration; Tan, Barış; Faculty Member; Department of Business Administration; College of Administrative Sciences and Economics; 28600We present an analytical model to analyze the operation of a productive cooperation network where producers cooperate on production capacity. Producers have limited capacity and have access to subcontractors at a higher cost. A single-unit auction-based allocation mechanism is proposed to allocate an arriving order based on the producers' cost structures and their current loads to maximize the total profit. We show that when the costs are private information, producers are willing to cooperate in order to increase their expected profit. Furthermore, it is shown that there is an equilibrium where producers bid their actual costs. The cooperation can also generate extra profit to cover a part of its operating expenses with this allocation mechanism. A continuous-time Markov chain model is utilized to evaluate the performance of the allocation mechanism where producers submit their myopic best response bids. The cooperation case is also compared with the no-cooperation case and also with the centralized operation of producers.Publication Open Access Do exogenous shocks help or hurt innovation performance of alliances? evidence from Ebola outbreak(Academy of Management, 2019) Tarakçı, Murat; Department of Business Administration; Arslan, Birgül; Faculty Member; Department of Business Administration; College of Administrative Sciences and EconomicsBuilding on attention-based view, we argue that exogenous shocks affect alliance performance by steering managerial attention. We find that while the innovation performance of Ebola alliances formed after the 2014 outbreak increased, performance of Influenza alliances decreased. Our study reveals negative spillover effects of industry shocks among related industry segments.Publication Open Access State foreclosure laws and the incidence of mortgage default(University of Chicago Press, 2014) Dudley, Evan; James, Christopher M.; Department of Business Administration; Demiroğlu, Cem; Faculty Member; Department of Business Administration; College of Administrative Sciences and Economics; 18073This study presents a numerical and an experimental study on an active vibration control system. The system includes a fully-clamped plate and two surface bonded piezoelectric actuators and a collocated velocity sensor at one of the actuator locations. One of the piezoelectric actuators is used for disturbance actuation and the other one is used for control actuation. A model based optimal velocity feedback controller is used as control algorithm. The disturbance and actuator models are obtained through experimental characterization of the plate under the effect of the disturbance source. A representative SIMULINK model is built in parallel to the development of the experimental setup in order to investigate performance of the controller for various control parameters. After the model based optimal controller is designed, performance of the optimal velocity feedback controller is validated with the experimental study by comparing the vibration suppression values at multiple modes of the structure. Results show that the developed control methodology effectively suppresses the vibration amplitudes at multiple modes of the structure and also vibration attenuation levels can be predicted accurately with the simulations for various controller design parameters. It is also demonstrated that using an optimal controller enhances the performance of the system as opposed to just using velocity feedback algorithm for the active vibration control of the smart plate.Publication Open Access Household demographics and preference for organic products in seven major food categories(Anadolu Üniversitesi, 2022) Department of Business Administration; Güler, Ali Umut; Faculty Member; Department of Business Administration; College of Administrative Sciences and Economics; 143349Amid increasing health concerns about industrially processed packaged consumer products, demand for organic products has risen in recent decades. Using rich panel data on food purchases of more than 60 thousand U.S. households, this study examines consumer profiles of organic products in seven major food groups with the aim of identifying household characteristics that predict preference for organic product options. The results of the regression analyses show that demand for organic products increases with income and education level. The preference for organic products is higher in younger households and peaks in the 30-34 age group, while it decreases in large households with more than four members. At the same time, the results show that consumption of organic products increases in households with a young child, especially in categories that typically form an important part of a young child's diet, such as eggs and dairy products. These results suggest significant nonlinearities in the effects of age and household size, as well as differences in the effects of demographic variables by product category, that should be taken into consideration in the marketing of organic products. / Endüstriyel olarak işlenmiş tüketici ürünleriyle ilgili sağlık endişelerinin artmasıyla birlikte, yakın dönemde organik ürünlere olan talep artmıştır. Bu çalışma, organik ürün tercihini belirleyen hanehali demografik özelliklerini ortaya koymak amacıyla, 60 binin üzerinde ABD hanehalkının gıda alımlarına ilişkin verişini kullanarak, yedi ana gıda grubu temelinde organik ürünlerin tüketici profillerini incelemektedir. Regresyon analizlerinden elde edilen sonuçlar, organik ürünlere olan talebin gelir ve eğitim düzeyi ile arttığını ortaya koymaktadır. Organik ürün tercihi genç hanelerde daha yüksek olup, 30-34 yaş grubunda en yüksek seviyeye çıkmakta, buna karşın dört ve daha çok birey içeren geniş haneler için düşüş göstermektedir. Küçük çocuklu evlerde, özellikle yumurta ve süt ürünleri gibi tipik olarak çocuk beslenmesinde önemli yeri olan gıda kategorilerinde organik ürünlerin payı artmaktadır. Bu bulgular, organik ürün pazarlamasında, demografik etmenlerde yaş ve hanehalkı büyüklüğüne göre ve ürün kategorisine göre oluşabilen tercih farklarının gözönünde bulundurulması gerektiğine işaret etmektedir.Publication Open Access Advance care plans: planning for critical healthcare decisions(The University of Chicago Press, 2022) Botti, Simona; Morwitz, Vicki G.; Department of Business Administration; Okutur, Nazlı Gürdamar; Faculty Member; Department of Business Administration; College of Administrative Sciences and Economics; 353043Advance care plans (ACPs) document personal values and healthcare preferences for critical situations where individuals cannot speak for themselves. Although ACPs can prevent receiving costly unwanted treatments and ensure receiving preferred treatments, few people have one. We examine factors associated with ACP engagement and design interventions to increase engagement. We find that ACP holders and nonholders largely have common values and preferences, which similarly vary with demographics. For example, older (vs. younger) individuals, regardless of ACP ownership, prefer to be able to care for themselves and to avoid prolonged end-of-life medical interventions. These two groups also differ in important ways: those who have or intend to create ACPs (vs. not) prefer avoiding invasive life-sustaining treatments and having a peaceful end of life. However, interventions that use these similarities and differences to increase ACP engagement are unsuccessful. We propose that structural approaches may be more effective in increasing ACP uptake.Publication Open Access Dynamic matching for real-time ride sharing(The Institute for Operations Research and the Management Sciences (INFORMS), 2020) Ward, Amy R.; Department of Business Administration; Özkan, Erhun; Faculty Member; Department of Business Administration; College of Administrative Sciences and Economics; 294016In a ride-sharing system, arriving customers must be matched with available drivers. These decisions affect the overall number of customers matched, because they impact whether future available drivers will be close to the locations of arriving customers. A common policy used in practice is the closest driver policy, which offers an arriving customer the closest driver. This is an attractive policy because it is simple and easy to implement. However, we expect that parameter-based policies can achieve better per-formance. We propose matching policies based on a continuous linear program (CLP) that accounts for (i) the differing arrival rates of customers and drivers in different areas of the city, (ii) how long customers are willing to wait for driver pickup, (iii) how long drivers are willing to wait for a customer, and (iv) the time-varying nature of all the aforementioned parameters. We prove asymptotic optimality of a forward-looking CLP-based policy in a large market regime and of a myopic linear program–based matching policy when drivers are fully utilized. When pricing affects customer and driver arrival rates and parameters are time homogeneous, we show that asymptotically optimal joint pricing and matching decisions lead to fully utilized drivers under mild conditions.