@article { author = {Babashahi, M. and Shahanaghi, K. and Gholamian, M.R. and Yavari, A.}, title = {A bi-objective hierarchical hub location model with facility failure}, journal = {Scientia Iranica}, volume = {27}, number = {4}, pages = {2009-2020}, year = {2020}, publisher = {Sharif University of Technology}, issn = {1026-3098}, eissn = {2345-3605}, doi = {10.24200/sci.2018.5358.1229}, abstract = {In the most past hub location problem (HLP) studies, failure probability is limited to a constant value; while in reality, it depends on various factors including natural disasters such as floods and earthquakes, commodity flow, institutional elements such as strikes, and etc. This paper looks into the problem of hub network design through a new model. The problem is to maximize the network reliability and to minimize the total routing cost simultaneously. In order to provide a more realistic model, the hub’s failure probabilities were considered as a function of the hub’s incoming traffic. Reserve hub elements are also taken into account in the model with the aim of increasing network reliability. To solve the model, a non-dominated sorting genetic algorithm (NSGA-II) is presented. The parameters of the algorithm are tuned using Taguchi method. The proposed solution is then carried out in a case study where the results confirm the acceptable performance of the model and also sensitivity analysis is performed in order to describe the effects of critical parameters into objective functions.}, keywords = {Hierarchical Hub Location,Backup Facility,Reliability,Hub Failure,NSGA-II}, url = {https://scientiairanica.sharif.edu/article_21155.html}, eprint = {https://scientiairanica.sharif.edu/article_21155_4a6077c7ed6afa58b40660f358deb3de.pdf} } @article { author = {Kumar Sinha, A. and Anand, A.}, title = {A holistic framework for lot sizing problem for fast-moving perishable products}, journal = {Scientia Iranica}, volume = {27}, number = {4}, pages = {2021-2039}, year = {2020}, publisher = {Sharif University of Technology}, issn = {1026-3098}, eissn = {2345-3605}, doi = {10.24200/sci.2018.5599.1363}, abstract = {One of the major challenges being faced by manufacturing companies today is the issue of addressing various aspects of perishable products in a supply chain environment. To address this issue, the integrated lot size problem for a perishable product has been investigated in the present work. The problem is modeled as a single vendor multiple buyer system. A variant of the truckload discount scheme is applied and the proposed model is formulated as a mixed integer program (MIP). The traditional warehouses are replaced by ‘cross-docks’ and situations in which, cross-docking would be more beneficial are highlighted. The problem of fleet selection is also addressed and various strategies to minimize the vendor cost are also highlighted for centralized and decentralized supply chains. Sensitivity analysis is then carried out on various input parameters such as setup cost at plant, variable transportation cost, fixed transportation cost, setup cost per order, holding cost and, lost cost, which underscores the significant impact of economies of scale in transportation on the total supply chain cost. Analysis of lead time-cost trade-off reveals that alternate modes of transportation could be explored, which significantly reduces the lead time of transportation, thereby minimizing the total supply chain cost.}, keywords = {Lot sizing,Fast moving perishable products,Supply chain,Cross-dock,Truckload discount}, url = {https://scientiairanica.sharif.edu/article_21204.html}, eprint = {https://scientiairanica.sharif.edu/article_21204_e9e761bd4dd552b53f86793bac643419.pdf} } @article { author = {Naz, F. and Abid, M. and Nawaz, T. and Pang, T.}, title = {Enhancing efficiency of ratio-type estimators of population variance by a combination of information on robust location measures}, journal = {Scientia Iranica}, volume = {27}, number = {4}, pages = {2040-2056}, year = {2020}, publisher = {Sharif University of Technology}, issn = {1026-3098}, eissn = {2345-3605}, doi = {10.24200/sci.2019.5633.1385}, abstract = {Numerous ratio-type estimators of the population variance are proposed in the existing literature based on different characteristics of the study as well as the auxiliary variable. However, mostly the existing estimators are based on the conventional measures of the population characteristics and their efficiency is dubious in the presence of outliers in the data. This study presents improved families of variance estimators under simple random sampling without replacement assuming that the information on some robust non-conventional location parameters of the auxiliary variable is known besides the usual conventional parameters. The bias and mean square error of the proposed families of estimators are obtained and the efficiency conditions are derived mathematically. The theoretical results are supplemented with the numerical illustrations by using real datasets which indicates the supremacy of the suggested families of estimators.}, keywords = {Auxiliary variable,Bias,Efficiency,Mean square error,Outliers,Ratio estimators}, url = {https://scientiairanica.sharif.edu/article_21219.html}, eprint = {https://scientiairanica.sharif.edu/article_21219_8eab7c9e67c5dc2885e48684f389c846.pdf} } @article { author = {Mahmoodirad, A. and Niroomand, S. and Hosseinzadeh Lotfi, F.}, title = {An effective solution approach to multi-objective fractional fixed charge problem with fuzzy parameters}, journal = {Scientia Iranica}, volume = {27}, number = {4}, pages = {2057-2068}, year = {2020}, publisher = {Sharif University of Technology}, issn = {1026-3098}, eissn = {2345-3605}, doi = {10.24200/sci.2018.50229.1588}, abstract = {A multi-objective fixed charge problem in existence of several fractional objective functions with triangular fuzzy parameters is considered in this study. The problem previously has been tackled only by Upmanyu and Saxena (2016) with a method containing wrong mathematical concepts (see the commentary of Kaur and Kumar (2017)). To overcome the shortcomings of the literature, an effective solution approach based on a typical goal programming approach is proposed to solve the problem for obtaining a Pareto-optimal solution. The proposed approach considers the shortcomings of the method of Upmanyu and Saxena (2016) and applies no ranking function of fuzzy numbers. In addition, the goal programming stage considers no preference from decision maker. The computational experiments provided by an example of the literature, prove the effectiveness of the proposed approach.}, keywords = {Fixed charge problem,Fractional objective function,Fuzzy theory,Goal,programming}, url = {https://scientiairanica.sharif.edu/article_21207.html}, eprint = {https://scientiairanica.sharif.edu/article_21207_c106eb359d1e0ace76ab5c33e27e1969.pdf} } @article { author = {Wu, Y. and Li, D. and Li, T.}, title = {Coordination of traditional and online group-buying channels considering website promotion effort}, journal = {Scientia Iranica}, volume = {27}, number = {4}, pages = {2069-2092}, year = {2020}, publisher = {Sharif University of Technology}, issn = {1026-3098}, eissn = {2345-3605}, doi = {10.24200/sci.2018.50750.1850}, abstract = {The development of modern technology and e-commerce have given rise to the emergence of many new selling channels. Among one of them, group-buying attracts numerous new customers rapidly due to the characters of deep discounts and great convenience. Although deep discounts create sales growth for sellers, it also causes the loss in their profit margins. Meanwhile, the business model of group-buying websites is not thoroughly understood in literature. Based on a Stackelberg game framework, this paper studies the equilibrium between a group-buying website and a seller. The optimal pricing and channel decisions of the seller and the optimal group-buying pricing and promotion effort decisions for the website are investigated to offer guidance for their businesses. We find that the total profit of the whole system could be hurt when the agreement price or revenue sharing contracts are adopted by the firms. We propose a revenue-cost sharing contract that could coordinate the total profit. Finally, we show how the scale of the seller and the website and the unit cost influence the optimal decisions in the equilibrium.}, keywords = {Group buying,dual channels,channel management,revenue coordination,Promotion effort}, url = {https://scientiairanica.sharif.edu/article_21190.html}, eprint = {https://scientiairanica.sharif.edu/article_21190_1a19fa16692114661d1a1ac2a3274b52.pdf} } @article { author = {Rostami, A. and Paydar, M.M. and Asadi-Gangraj, E.}, title = {Dynamic virtual cell formation considering new product development}, journal = {Scientia Iranica}, volume = {27}, number = {4}, pages = {2093-2107}, year = {2020}, publisher = {Sharif University of Technology}, issn = {1026-3098}, eissn = {2345-3605}, doi = {10.24200/sci.2018.51130.2021}, abstract = {Nowadays, factories should be coordinated with changes in the dynamic environment due to the intense competition in the businesses. Different strategies and systems are existing to help factories in a dynamic situation. In this article, a new multi-objective mathematical model is presented by the implementation of dynamic virtual cellular manufacturing and also considering new product development which enables factories to be successful in their business. This paper contains three objectives including maximizing the total profits of the factory in all the periods, the grouping efficacy and also the number of the new product. After linearization of the proposed model, multi-choice goal programming with utility function is used to solve the model. In addition, a case study has been conducted in the real world to show the effectiveness of the proposed model and finally, the results show that the integration of virtual cellular manufacturing with new product development can be helpful for managers and companies and leads to more efficiency.}, keywords = {Dynamic virtual cell formation,Grouping efficacy,New Product Development,Goal Programming,bi-objective optimization}, url = {https://scientiairanica.sharif.edu/article_21192.html}, eprint = {https://scientiairanica.sharif.edu/article_21192_1b54957eaa664b53b8447fee8a5530c9.pdf} } @article { author = {Sabzevari, M. and Sajadi, S.M. and Hadjimolana, SM.}, title = {Supply chain reconfiguration for new product development through risk management approach}, journal = {Scientia Iranica}, volume = {27}, number = {4}, pages = {2108-2126}, year = {2020}, publisher = {Sharif University of Technology}, issn = {1026-3098}, eissn = {2345-3605}, doi = {10.24200/sci.2019.51175.2039}, abstract = {We are living in an era that innovation is increasingly growing and products’ lifetime is decreasing. In this situation new product development is an advantage that makes it possible to survive in the competitive market. However, risks are unavoidable in new product development in any industries. Therefore, identifying, management and mitigation of risks are considered of high significance for companies. By taking risk management into account, this study introduces a new, multi-objective, mathematical model for supply chain configuration in the presence of a new product. The considered supply chain is multi-echelon, multi-resources, multi-period, and multi-product. In order to manage the risk in this supply chain, appropriate mitigation strategies were chosen from various risk response strategies considering their cost and effectiveness as well as influence of each choice on supply chain was also taken into account in the mathematical model. The assumed model explored the optimum tactical and operational SCM decisions. The ability of the model was assessed by solving an example. The result showed that the choice of various response strategies as well as new product production influenced supply chain configuration.}, keywords = {Supply Chain Reconfiguration,New Product Development,Risk Management,Fast moving consumer goods,Goal Programming}, url = {https://scientiairanica.sharif.edu/article_21267.html}, eprint = {https://scientiairanica.sharif.edu/article_21267_ad4720cbf19af2f7713189286b6ba113.pdf} } @article { author = {Kumar, T. and Bajaj, R.K. and Dilshad Ansari, M.}, title = {On accuracy function and distance measures of interval-valued Pythagorean fuzzy sets with application to decision making}, journal = {Scientia Iranica}, volume = {27}, number = {4}, pages = {2127-2139}, year = {2020}, publisher = {Sharif University of Technology}, issn = {1026-3098}, eissn = {2345-3605}, doi = {10.24200/sci.2019.51579.2260}, abstract = {The notion of interval-valued Pythagorean fuzzy sets permits four important parameters, i.e., membership degree, non-membership degree, and a pair of values strength of commitment and direction of commitment, to a given set to have an interval value in dealing with imprecise information. In the present communication, a new accuracy function is being provided to overcome the shortcomings of the existing score and available accuracy functions for interval-valued Pythagorean fuzzy sets. The validity of the proposed accuracy function has been discussed in detail through the illustrative examples. Further, a new interval-valued Pythagorean fuzzy $p$-distance measure for interval-valued Pythagorean fuzzy numbers has been proposed and used in context with the existing weighted averaging operators. Finally, in view of the proposed accuracy function, distance measure and weighted averaging operators, a numerical example of multi-criteria decision-making problem has been solved to validate the proposed methodology.}, keywords = {Interval-valued Pythagorean Fuzzy Numbers,Score Function,Accuracy Function,distance measures,Weighted Averaging Operators}, url = {https://scientiairanica.sharif.edu/article_21256.html}, eprint = {https://scientiairanica.sharif.edu/article_21256_85c423ff61dd460b24d1d0db8233d0c2.pdf} } @article { author = {Abrishami, S.J. and Vahdani, H. and Rezaee, B.}, title = {An integrated lot-sizing model with supplier and carrier selection and quantity discounts considering multiple products}, journal = {Scientia Iranica}, volume = {27}, number = {4}, pages = {2140-2156}, year = {2020}, publisher = {Sharif University of Technology}, issn = {1026-3098}, eissn = {2345-3605}, doi = {10.24200/sci.2019.5155.1125}, abstract = {Because of growing competition in the global markets and the vital role of suppliers in business success, the subject of supplier selection has attracted many researchers and practitioners during the recent years. In addition to the supplier selection, the order quantity discount provided by the suppliers, is considered through a new mixed-integer linear programming (MILP) model involving a manufacturer with multiple products and multiple purchasing items over multiple periods. According to the proposed model, the manufacturer purchases different amount of raw materials from selected suppliers in order to produce different products. Customers’ demands are fulfilled by minimizing the total purchase, inventory, production, and transportation costs over a multi-period planning horizon. Since the problem is NP-hard, an efficient genetic algorithm (GA) is used to solve the large-scale real-world instances. The results are compared with results from the exact approach wherever possible in order to investigate the efficiency of the algorithm.}, keywords = {Supplier selection,Inventory management,Quantity discounts,Carrier selection,Genetic Algorithm}, url = {https://scientiairanica.sharif.edu/article_21362.html}, eprint = {https://scientiairanica.sharif.edu/article_21362_3942211fa4b951e9d1d7f03fa69a1756.pdf} } @article { author = {Sadjadi, S.J. and Gorji Ashtiani, M. and Makui, A. and Ramezanian, R.}, title = {A mathematical model for competitive location problem with product selection}, journal = {Scientia Iranica}, volume = {27}, number = {4}, pages = {2157-2176}, year = {2020}, publisher = {Sharif University of Technology}, issn = {1026-3098}, eissn = {2345-3605}, doi = {10.24200/sci.2018.51736.2337}, abstract = {In this paper, a new competitive location problem for a chain is considered. The chain’s owner can offer a variety of products. The model’s objective is to determine both the location of the new facilities and the optimal product type for each opened facility. The patronizing behavior of the customers is based on Huff rule and the location of new facilities is selected from a set of potential sites. As a result, the model is a nonlinear integer programming problem and for solving the proposed model, the problem is reformulated as a mixed integer linear programming and therefore a standard optimization solver can be used for obtaining the optimal solutions for small and medium-size problems. To cope with large-size problems, we develop two methods: 1) a heuristic method for a special case and 2) a hybrid heuristic-firefly algorithm for general cases. By using the proposed model, it is shown numerically that in multi-product industries in which owner of the facilities is able to offer different types of products, in addition to the optimal location, it is necessary to determine the best products. In the end, a real-world case study for locating a new bakery is presented.}, keywords = {Competitive location,product variety,Huff rule,mixed integer linear programming,location-product,Hybrid heuristic- filrely algorithm}, url = {https://scientiairanica.sharif.edu/article_21152.html}, eprint = {https://scientiairanica.sharif.edu/article_21152_c6f22af5187780a73473256dedcd2830.pdf} }