@article {6869, title = {Optimal facility location and customer routing: Modeling client preference assignment under the risk of disruptions}, journal = {IIE Transactions}, year = {Submitted}, author = {Hiassat, A. and Ozaltin, O.Y. and Erenay, F.S.} } @article {6863, title = {Optimal vaccine administration policies using multi-dose vials of different sizes}, journal = {(2nd Round) Production and Operations Management}, year = {Submitted}, author = {Nemutlu, G.S. and Erenay, F.S. and Ozaltin, O.Y. and Papastergiou, J. and Waite, N.} } @article {28968, title = {Spatial separability in hub location problems with an application to brain connectivity networks}, journal = {INFORMS Journal on Optimization}, volume = {2}, year = {2020}, pages = {320{\textendash}346}, author = {Khaniyev, T. and Elhedhli, S. and Erenay, F.S.} } @article {23844, title = {Economic and environmental impacts of emission mitigation in petroleum refineries}, journal = {Sustainability}, volume = {11}, year = {2019}, pages = {3771-3801}, author = {[P.2] Alnahdi, A. and Elkamel, A. and Shaik, M.A. and Al-Sobhi, S.A. and Erenay, F.S.} } @article {23845, title = {Financial Audit of Wastage of Anticancer Drugs: Pilot Study from a Tertiary Care Centre of India}, journal = {Indian Journal of Cancer}, volume = {56}, year = {2019}, pages = {99-100}, author = {Erenay, F.S. and Horton, S.} } @article {23850, title = {Integrating simulation in optimal synthesis and design of natural gas upstream processing networks}, journal = {Industrial \& Engineering Chemistry Research}, volume = {57}, year = {2018}, pages = {5792{\textendash}5804}, author = {Alsobhi, S. and Shaik, M. and Elkamel, A. and Erenay, F.S.} } @article {23847, title = {Shipment consolidation with two demand classes: Rationing the dispatch capacity}, journal = {European Journal of Operational Research}, volume = { 270}, year = {2018}, pages = {171-184}, author = {Satir, B. and Erenay, F.S. and Bookbinder, J.} } @article {23849, title = {Simulation-optimization framework for synthesis and design of natural gas downstream utilization networks}, journal = {Energies}, volume = {11}, year = {2018}, pages = {362-381}, author = {Al-Sobhi, S.A. and Shaik, M.A. and Elkamel, A. and Erenay, F.S.} } @article {23848, title = {Structure detection in mixed integer programs}, journal = {INFORMS Journal on Computing}, volume = { 30}, year = {2018}, pages = {570-587}, author = {Khaniyev, T. and Elhedhli, S. and Erenay, F.S.} } @article {23846, title = {Tollgate-based progression pathways of ALS patients}, journal = {Journal of Neurology}, volume = {266 }, year = {2018}, pages = {755-765}, author = {Dalgic, O.O. and Erenay, F.S. and Ozaltin, O.Y. and Pasupathy, K. and Sir, M. and Crum, B.A.} } @article {6827, title = {Deriving effective vaccine allocation strategies for pandemic influenza: Comparison of an agent-based simulation and a compartmental model}, journal = {PLoS ONE}, volume = {12}, year = {2017}, pages = {1-19}, abstract = {

Individuals are prioritized based on their risk profiles when allocating limited vaccine stocks during an influenza pandemic. Computationally expensive but realistic agent-based simulations and fast but stylized compartmental models are typically used to derive effective vaccine allocation strategies. A detailed comparison of these two approaches, however, is often omitted. We derive age-specific vaccine allocation strategies to mitigate a pandemic influenza outbreak in Seattle by applying derivative-free optimization to an agent-based simulation and also to a compartmental model. We compare the strategies derived by these two approaches under various infection aggressiveness and vaccine coverage scenarios. We observe that both approaches primarily vaccinate school children, however they may allocate the remaining vaccines in different ways. The vaccine allocation strategies derived by using the agent-based simulation are associated with up to 70\% decrease in total cost and 34\% reduction in the number of infections compared to the strategies derived by using the compartmental model. Nevertheless, the latter approach may still be competitive for very low and/or very high infection aggressiveness. Our results provide insights about potential differences between the vaccine allocation strategies derived by using agent-based simulations and those derived by using compartmental models.

}, url = {https://doi.org/10.1371/journal.pone.0172261}, author = {Dalgic, O.O. and Ozaltin, O.Y. and Ciccotelli, W.A. and Erenay, F.S.} } @proceedings {6857, title = {Exploiting spatial separability of uncapacitated single allocation p-hub median problems}, journal = {14th International Symposium On Locational Decisions}, year = {2017}, author = {Khaniyev, T. and Elhedhli, S. and Erenay, F.S.} } @article {6620, title = {Improving configuration of complex production lines via simulation-based optimization}, journal = {Computers and Industrial Engineering}, volume = {109}, year = {2017}, pages = {295-312}, abstract = {

Optimizing the configuration of a complex production line is an NP-hard problem in various machine settings. Solving real-life-size instances of this problem becomes a more common challenge because the current trend of reshoring induces multi-national firms to transfer manufacturing facilities from workforce-intensive to capital-intensive production environments which usually require re-configuration of the transferred manufacturing systems according to the availability of better machinery in a capital-intensive environment. This paper focuses on the problem of optimizing production line configuration and proposes several simulation-based optimization approaches based on myopic search, ant-colony, simulated annealing, and response-surface methodologies. We investigate the relative performances of these proposed algorithms on a real-life manufacturing system transfer case in automotive industry according to solution quality and computation-time metrics under different parameter scenarios. Thus, our numerical results may guide the decision makers in choosing a suitable solution approach for this problem depending on the problem size and time availability. Our results also illustrate that ant-colony optimization, a methodology not widely applied in simulation-based optimization, provides high-solution quality for this problem when matched-up with a myopic search to find a good initial solution.

}, author = {Yegul, F.*, and Erenay, F.S., and Striepe, S., and Yavuz, M.,} } @article {6830, title = {Cost-effectiveness of alternative colonoscopy surveillance strategies to mitigate metachronous colorectal cancer incidence}, journal = {Cancer}, volume = {122}, year = {2016}, pages = {2560-2570}, abstract = {

BACKGROUND

The incidence of metachronous colorectal cancer (MCRC) among colorectal cancer (CRC) survivors varies significantly, and the optimal colonoscopy surveillance practice for mitigating MCRC incidence is unknown.

METHODS

A cost-effectiveness analysis was used to compare the performances of the US Multi-Society Task Force guideline and all clinically reasonable colonoscopy surveillance strategies for 50- to 79-year-old posttreatment CRC patients with a computer simulation model.

CONCLUSIONS

The US guideline might be improved by a slight increase in the surveillance intensity at the expense of moderately increased cost. More research is warranted to explore the benefits/harms of such practices.

}, url = {http://onlinelibrary.wiley.com/doi/10.1002/cncr.30091/full}, author = {Erenay, F.S. and Alagoz, O. and Banerjee, R. and Said, A. and Cima, R.R.} } @article {6837, title = {Dynamic optimization of lurgi type methanol reactor using hybrid GA-GPS algorithm: The optimal shell temperature trajectory and carbon dioxide utilization}, journal = {Industrial \& Engineering Chemistry Research}, volume = {55}, year = {2016}, pages = {1164-1173}, abstract = {

At present, methanol is mostly produced from syngas, derived from natural gas through steam methane reforming (SMR). In a typical methanol production plant, unreacted syngas is recycled for mixing with natural gas and both used as fuel in the reformer furnace resulting in carbon dioxide (CO2) emissions from the flue gases emitted into the atmosphere. However, CO2 can be captured and utilized as feedstock within the methanol synthesis process to enhance the productivity and efficiency. To do so, dynamic optimization approaches to derive the ideal operating conditions for a Lurgi type methanol reactor in the presence of catalyst deactivation are proposed to determine the optimal use of recycle ratio of CO2 and shell coolant temperature without violating any process constraints. In this context, this study proposes a new approach based on a hybrid algorithm combining genetic algorithm (GA) and generalized pattern search (GPS) derivative-free methodologies to provide a sufficiently good solution to this dynamic optimization problem. The hybrid GA-GPS algorithm has the advantage of sequentially combining GA and GPS logics: GA, as the most popular evolutionary algorithm, effectively explore the landscape of the fitness function and identify promising basins of the search space, whereas GPS efficiently searches existing basins in order to find an approximately optimal solution. The simulation results showed that implementing the shell temperature trajectory derived by the proposed approach with 5\% recycle ratio of CO2 increased the production of methanol by approximately 2.5\% compared to the existing operating conditions.

}, url = {http://pubs.acs.org/doi/full/10.1021/acs.iecr.5b02918}, author = {Alarifi, A. and Liu, Z. and Erenay, F.S. and Elkamel, A. and Croiset, E.} } @proceedings {6858, title = {Optimal distribution of the influenza vaccine}, journal = {2014 Winter Simulation Conference}, year = {2014}, pages = {1411-1420}, address = {Proceedings of the 2014 Winter Simulation Conference}, author = {Ozaltin, O.Y. and Dalgic, O.O. and Erenay, F.S.} } @article {6839, title = {Optimizing Colonoscopy Screening for Colorectal Cancer Prevention and Surveillance}, journal = {Manufacturing \& Service Operations Management}, volume = {16}, year = {2014}, pages = {381-400}, abstract = {

Millions of Americans undergo colonoscopy screening for colorectal cancer (CRC) prevention and surveillance every year. The efficiency of colonoscopy operations depends on how often patients are screened, which is a complex and controversial decision, as reflected by the discrepancy between clinical practice and guidelines. We develop a partially observable Markov decision process to optimize colonoscopy screening policies for the objective of maximizing total quality-adjusted life years. Our model incorporates age, gender, and risk of having CRC into the screening decisions and therefore provides a novel framework for personalized CRC screening. In addition to deriving the maximum attainable benefit from colonoscopy screening, which reflects the opportunity cost of following current guidelines, our results have several policy implications. Using clinical data, we show that the optimal colonoscopy screening policies may be more aggressive than the guidelines under some conditions. Optimal screening policies recommend that females with CRC history undergo colonoscopy more frequently than males. In contrast, females without CRC history should be screened less frequently than males. This result, which was not recognized before, signifies the role of gender in optimal CRC screening decisions.

}, url = {https://doi.org/10.1287/msom.2014.0484}, author = {Erenay, F.S. and Alagoz, O. and Said, A.} } @article {6840, title = {A survey of optimization models on cancer chemotherapy treatment planning}, journal = {Annals of Operations Research}, volume = {221}, year = {2014}, pages = {331-356}, abstract = {

While chemotherapy is an effective method for treating cancers such as colorectal cancer, its effectiveness may be dampened by the drug resistance and it may have significant side effects due to the destruction of normal cells during the treatment. As a result, there is a need for research on choosing an optimal chemotherapy treatment plan that minimizes the number of cancerous cells while ensuring that the total toxicity is below an allowable limit. In this paper, we summarize the mathematical models applied to the optimal design of the cancer chemotherapy. We first elaborate on a typical optimization model and classify relevant literature with respect to modeling methods: Optimal control model (OCM) and others. We further classify the OCM models with respect to the solution method used. We discuss the limitations of the existing research and provide several directions for further research in optimizing chemotherapy treatment planning.

}, url = {https://link.springer.com/article/10.1007/s10479-011-0869-4}, author = {Shi, J. and Alagoz, O. and Erenay, F.S. and Su, Q.} } @article {6845, title = {Potential of Standardization and Certification for Successful Lean Implementations}, journal = {Journal of Enterprise Transformation}, volume = {3}, year = {2013}, pages = {211-232}, abstract = {

A successful lean implementation is the key for lean enterprise transformation. However, many companies are struggling to change the culture in their system and are having problems in adapting lean principles. In this article, we discuss whether lean standardization and professional lean certification (LS\&C) has the potential to promote successful lean implementation leading to a lean enterprise transformation. For this purpose, we first analyzed the concepts of LS\&C and reviewed the existing ones, including J4000 through literature review and personal communications with lean experts. We also conducted a survey among lean professionals to get feedback about their attitudes toward LS\&C. The survey results suggest that there is significant support for LS\&C, as around 60\% of the survey attendants believe LS\&C would eliminate problems in implementing lean principles. However, the awareness of existing standards among lean practitioners is very low, which indicates the need for development of new lean standards and/or better promotion. Our survey results also suggest that the level of support for lean standardization depends on many factors, including positions of the professionals and extent of companies{\textquoteright} lean experience.

}, url = {http://dx.doi.org/10.1080/19488289.2013.816809}, author = {Degirmenci, T. and Yegul, F. and Erenay, F.S. and Striepe, S. and Yavuz, M.} } @article {6847, title = {A broader view of designing the liver allocation system}, journal = {Operations Research}, volume = {60}, year = {2012}, pages = {757-770}, abstract = {

We consider the problem of designing an efficient system for allocating donated livers to patients waiting for transplantation. The trade-off between medical urgency and efficiency is at the heart of the liver allocation problem. We model the transplant waiting list as a multiclass fluid model of overloaded queues, which captures the disease evolution by allowing the patients to switch between classes, i.e., health levels. We consider the bicriteria objective of minimizing total number of patient deaths while waiting for transplantation (NPDWT) and maximizing total quality-adjusted life years (QALYs) through a weighted combination. On one hand, under the objective of minimizing NPDWT, the current policy of United Network for Organ Sharing (UNOS) emerges as the optimal policy, providing a theoretical justification for the current practice. On the other hand, under the metric of maximizing QALYs, the optimal policy is an intuitive dynamic index policy that ranks patients based on their marginal benefit from transplantation, i.e., the difference in benefit with versus without transplantation. Finally, we perform a detailed simulation study to compare the performances of our proposed policies and the current UNOS policy along the following metrics: total QALYs, NPDWT, number of patient deaths after transplantation, number of total patient deaths, and number of wasted livers. Numerical experiments show that our proposed policy for maximizing QALYs outperforms the current UNOS policy along all metrics except the NPDWT.

}, url = {https://doi.org/10.1287/opre.1120.1064}, author = {Akan, M. and Alagoz, O. and Ata, B. and Erenay, F.S. and Said, A.} } @proceedings {6859, title = {Optimal colorectal cancer screening to balance life-year savings and costs}, journal = {34th Annual Meeting of the Society for Medical Decision Making}, year = {2012}, address = {Proceedings of the 34th Annual Meeting of the Society for Medical Decision Making}, author = {Erenay, F.S. and Alagoz, O. and Said, A.} } @article {6848, title = {Modeling the natural history of metachronous colorectal cancer under colonoscopy screenings}, journal = {Medical Decision Making}, volume = {31}, year = {2011}, pages = {611-624}, abstract = {

Objectives

Some aspects of the natural history of metachronous colorectal cancer (MCRC), such as the rate of progression from adenomatous polyp to MCRC, are unknown. The objective of this study is to estimate a set of parameters revealing some of these unknown characteristics of MCRC.

Methods

The authors developed a computer simulation model that mimics the progression of MCRC for a 5-year period following the treatment of primary colorectal cancer (CRC). They obtained the inputs of the simulation model using longitudinal data for 284 CRC patients from the Mayo Clinic, Rochester.

Results

Five-year MCRC incidence and all-cause mortality were 7.4\% and 12.7\% in the patient cohort, respectively. Statistical analysis showed that 5-year MCRC incidence was associated with gender (P = 0.05), whereas both all-cause and CRC-related mortalities were associated with age (P \< 0.001 and P = 0.01). Estimated annual probabilities of progression from adenomatous polyp to MCRC and from MCRC to metastatic MCRC were 0.14 and 0.28, respectively. Annual probabilities of mortality after MCRC and metastatic MCRC treatments were estimated to be 0.06 and 0.26, respectively. The estimated annual probability of mortality due to undetected MCRC was 0.16.

Conclusions

The results imply that MCRC, especially in women, may be more common than suggested by previous studies. In addition, statistics derived from the clinical data and results of the simulation model indicate that gender and age affect the progression of MCRC.

}, url = {10.1177/0272989X10391809} } @article {6855, title = {New solution methods for single machine bicriteria scheduling problem: Minimization of average flowtime and number of tardy jobs}, journal = {European Journal of Operational Research}, volume = {201}, year = {2010}, pages = {89-98}, abstract = {

We consider the bicriteria scheduling problem of minimizing the number of tardy jobs and average flowtime on a single machine. This problem, which is known to be NP-hard, is important in practice, as the former criterion conveys the customer{\textquoteright}s position, and the latter reflects the manufacturer{\textquoteright}s perspective in the supply chain. We propose four new heuristics to solve this multiobjective scheduling problem. Two of these heuristics are constructive algorithms based on beam search methodology. The other two are metaheuristic approaches using a genetic algorithm and tabu-search. Our computational experiments indicate that the proposed beam search heuristics find efficient schedules optimally in most cases and perform better than the existing heuristics in the literature.

}, url = {http://www.sciencedirect.com/science/article/pii/S0377221709001088}, author = {Erenay, F.S. and Toptal, A. and Sabuncuoglu, I. and Tiwari, M.K.} } @inbook {6856, title = {Operations research models for cancer screening}, booktitle = {Encyclopedia of Operations Research and Management Science}, year = {2010}, abstract = {

Early diagnosis through screening is an effective means of decreasing the death rate from cancer, the second leading cause of death in the US, since most cancers are now curable if detected early. On the other hand, the interventional procedures that result from detected abnormalities (both false and true positives) during screening and the significant cost of population-based screening of asymptomatic individuals require a careful analysis of the benefits and risks of screening in both utility and economic terms. In this article, we summarize the studies applying Operations Research (OR) tools to investigate issues related to cancer screening. In particular, we review OR studies considering cancer screening that are either briefly described or not mentioned in previous review articles. We classify relevant literature by cancer type including breast cancer, colorectal cancer, and cervical cancer. We also discuss several issues for future research in cancer screening.

}, url = {http://onlinelibrary.wiley.com/doi/10.1002/9780470400531.eorms0597/abstract?userIsAuthenticated=false\&deniedAccessCustomisedMessage=}, author = {Alagoz, O. and Ayer, T. and Erenay, F.S.} } @proceedings {6860, title = {Optimal colonoscopy screening policies for colorectal cancer prevention and surveillance}, journal = {32nd Annual Meeting of the Society for Medical Decision Making}, year = {2010}, address = {Proceedings of the 32nd Annual Meeting of the Society for Medical Decision Making}, author = {Erenay, F.S. and Alagoz, O. and Said, A.} } @proceedings {6861, title = {Optimizing liver allocation policy}, journal = {60th Annual Meeting of the American Association for the Study of Liver Diseases}, year = {2009}, address = {Proceedings of the 60th Annual Meeting of the American Association for the Study of Liver Diseases (AASLD)}, author = {Said, A. and Erenay, F.S. and Akan, M. and Ata, B. and Alagoz, O.} } @proceedings {6862, title = {Simulation of secondary colorectal cancer under colonoscopy screenings}, journal = {30th Annual Meeting of the Society for Medical Decision Making}, year = {2008}, address = {Proceedings of the 30th Annual Meeting of the Society for Medical Decision Making}, author = {Erenay, F.S. and Alagoz, O. and Banerjee, R. and Cima, R.R.} }