RAIRO - Operations Research (28047303)58(3)pp. 2445-2479
This paper aims to develop and simulate a green automotive supply chain model (ASC) consisting of one supplier, one manufacturer, and two types of products (green and non-green) under disruption risks (DRs). The greening effort (i.e., electric vehicle production) is considered for both the supplier and the manufacturer. In our modeling, we include the local government intervention (GI) and their incentivization of manufacturers to produce greener products. Moreover, the effectiveness of centralized versus decentralized supply chain integration strategies in coping with disruption consequences was explored. A mathematical pricing model based on game theory is designed to maximize the total profit for both integrated and decentralized systems. The model examines the effects of the greening effort on the supply chain (SC) members with eight disruption scenarios, including Extra Production and Surplus Inventory. Simulating numerical examples reveals that the Extra Production type of disruption increase the profitability in different scenarios. Conversely, the Surplus Inventory disruption reduces profitability. Moreover, a channel coordination through cost sharing contract in the presence of disruption sharing was developed. GI and the cost-sharing contract increase the SC profit. The managerial implications of our findings are also discussed in this paper. © The authors. Published by EDP Sciences, ROADEF, SMAI 2024.
Computers and Industrial Engineering (03608352)181
This paper presents a game-theoretic framework of competition for two packaging companies. The first one is a traditional packaging firm that employs new raw materials in its packaging and invests in innovative packaging solutions. In contrast, the other takes advantage of a combination of new and post-consumer-recycled (PCR) material based on a cost saving strategy. The model incorporates the price and quality of the product as well as its packaging and is implemented on packaging firms with the same source of manufacturer/importer. Two different scenarios are considered with the potential to push companies towards sustainable solutions; namely the existence of eco-conscious consumers and government tax on the new raw material packaging. The problem is established as a two-stage game, and the optimal level of investment in packaging innovation, the optimal ratio of PCR material and the optimal retail prices are derived, all in equilibrium. A real-world example and also parametric and sensitivity analysis are provided and valuable insights are derived. The results indicate that current proposed virgin tax plans do not provide a strong incentive towards sustainable packaging, whereas eco-conscious customers give this impetus. It was also observed that the imposed virgin tax does not impede innovation investment in virgin packaging companies. © 2023 Elsevier Ltd
International Journal of Management Science and Engineering Management (17509653)18(4)pp. 249-265
This article investigates inventory replenishment, advertising, and pricing decisions for perishable products with fixed expiration dates. Specifically, the problem is modelled using mixed-integer nonlinear programming to maximize the retailer’s total profit on an infinite planning horizon. Several assumptions are made to formulate the problem: i) the demand is considered a multivariate function of freshness, selling price, displayed inventory level, and advertisement frequency; ii) the holding cost of inventory increases linearly as the product ages; iii) the ending inventory is not necessarily zero. A search algorithm is proposed to solve this problem. The impact of each parameter on the optimal solution is investigated using sensitivity analysis. The advertising frequency determined via this model is an optimal compromise between advertising costs and yield. This model can be applied to reduce perishable food waste and meet the rising demand for fresh food. © 2022 International Society of Management Science and Engineering Management.
International Journal of Services and Operations Management (17442370)45(3)pp. 332-354
This paper considers a green inventory-routing problem (IRP) for perishable items in a two-level supply chain including a distributor (manufacturer/plant) and some retailers. Each item has a fixed expiry date. The product price depends on its age. The retailer demand for each product is fixed. The product cannot be sold after the expiry date. The possibility of hiring extra space for holding excessive amounts of inventory and hiring vehicles to exploit the advantage of the higher number of deliveries are considered. The problem is formulated to a mixed-integer linear programming (MILP) model. Some small, medium and large-sized random generated samples are solved using OPL software and a proposed combined ant-generic algorithm. The results show the positive effect of partial outsourcing on the amount of profit. Furthermore, the volume of orders is influenced by taking the environmental effects of transportation into account. Copyright © 2023 Inderscience Enterprises Ltd.
International Journal of Management Science and Engineering Management (17509653)18(2)pp. 77-87
One of the most important tools is an appropriate pricing mechanism to attract more customers and increase profits. The retailers’ main question is how to set the prices and inventory policies to maximize profit in a competitive heterogeneous market in presence of non-zero lead time and lost sales. A reinforcement learning algorithm is proposed to create appropriate decision-making mechanisms for pricing. A coordinated inventory policy in a competitive environment reduces logistic costs and leads to a higher profit. We use a reinforcement learning algorithm to investigate the performance of a retailer in a competitive environment. An agent-based modeling experimental environment combined with a simulation-optimization method in which a virtual market has been reproduced is used. The market is not homogeneous with respect to customer behavior. It is assumed that the retailer uses (R, Q) policy where the lead time is a fixed amount (L), and the shortage is permissible. The quality, distance, service level, and price are factors that influence customers’ choices. The simulation results for some randomly generated examples show that the algorithm in the competitive environment can make more profit than other available methods and the combined utilization of simulation-optimization methods has been able to find better solutions for the hybrid model of pricing and inventory management considering customer behavior. The results of simulation for three different categories of customers (more sensitive to price, equally sensitive to price, quality and service level, and more sensitive to quality (indicate that the average profit for the proposed algorithm is higher than that of other examined algorithms. © 2023 International Society of Management Science and Engineering Management.
Operational Research (11092858)23(4)
The range-adjusted measure (RAM) as one of the non-radial data envelopment analysis (DEA) models has been broadly used in the assessment of decision-making units (DMUs). In many situations, the DMUs have a multi-component (network) structure, where the output of each component can be used as the input of another component, which is referred to as intermediate output. Various methods with different forms of production possibility sets (PPSs) have been suggested to formulate the intermediate output in efficiency calculations that link network components and each of these methods leads to different efficiency scores. These different forms of PPSs include independent, relational, and cooperative, which can appraise the efficiency of a DMU from internal and external perspectives. This paper aims to clarify the relationship among different forms of PPSs for the network RAM-DEA model from internal and external perspectives by emphasizing the development of a network RAM-DEA model. This study shows that from internal evaluation, a DMU with a network structure may operate efficiently while it is inefficient from external evaluation. This study proves that to evaluate a DMU with a network structure, the cooperative form of PPS is more suitable from both internal and external perspectives. The independent form of PPS does not exactly define the relationships among the components, so it is not recommended for computing the efficiency of a network. Models associated with the relational form of PPS may cause excess supply (waste) in the network, which is not appropriate for internal evaluation. Finally, a real example illustrates the applicability of the presented model. © 2023, The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.
Computers and Industrial Engineering (03608352)170
In this article, we integrate dynamic slot allocation and inventory management to improve liner shipping decisions. Multi-leg revenue management concepts are used to model the problem of marine transporting full and empty containers. The model considers market distinctions, service diversity, and no-shows. The transportation of empty containers is planned to balance the inventory of empty containers in the ports. The problem is formulated as an integer program. Our objective is to maximize the total profit (revenue from shipping full containers minus the overall costs of transporting, leasing, and holding empty containers). An illustrative example based on Iranian liner shipping is solved, and the sensitivity of the results is analyzed. To evaluate the proposed deterministic model, we compare its results to those of the first come first serve (FCFS) method in a stochastic environment using simulation. A comparison between the proposed and traditional FCFS models shows a significant increase in profit. © 2022
Sustainable Energy Technologies and Assessments (22131388)52
Iran's electricity distribution network (EDN) includes three stages of generation, transmission, and distribution, with different types of input and output criteria and complex communications with both parallel and serial structures. This study formulates a Fuzzy Network DEA (FNDEA) model for assessing the efficiency of Iran's EDNs components with sustainability considerations and uncertain data. In order to utilize all input and output criteria, this study also proposes a fuzzy linear programming model to determine the optimal lower bound for all input and output weights. Furthermore, appropriate policies are suggested based on the strengths and weaknesses of each EDN to improve its efficiency. Finally, a sensitivity analysis has been implemented to validate the proposed model. The results of the present study reveal that the transmission stage performed better than the generation and distribution stages. It also shows that the distribution stage has the greatest impact on the overall performance of Iran's EDN. © 2022 Elsevier Ltd
International Journal of Mathematics in Operational Research (17575850)22(1)pp. 1-25
Managing the inventory of perishable items is a vital task in the supply chain. The demand for some deteriorating items is influenced by many factors that make their management a complicated task. Therefore, it is important to take multiple key factors into account to develop a more realistic model. In this paper, an inventory model for non-instantaneous deteriorating items is proposed, for the case where the quality and quantity of the item decrease over time. The demand is an additive, continuous, and differentiable function of price, stock level, and also age of the product. The deterioration starts after a fixed period with a constant rate and the shortage is not allowed. Permissible delay in payment and time value of money are also considered in the model. First, we formulate the problem in a piecewise mixed-integer nonlinear programming model. We then propose an algorithm to solve a number of examples. Copyright © 2022 Inderscience Enterprises Ltd.
Journal of Engineering Design (14661837)33(1)pp. 15-38
Considering the integrative design, production, and marketing policies for a configurable product family (CPF) (such as automobile, computer, cell phone) in decision making in a simultaneous manner is essential. This paper aims to provide a profit-maximisation model for integrating policies for CPFs by optimising the main variables of product configuration selection, components’ supply policy, price, and modules warranty lengths for each product. The existing models are not concerned with all these variables. Discrete decisions should be made on selecting the appropriate components for different modules and whether to buy or make them; simultaneously, the price and warranty are determined. The proposed model is a mixed-integer nonlinear problem and solved through a Genetic Algorithm (GA) and an adapted Particle Swarm Optimization (PSO) algorithm. The results of applying GA and PSO for different numerical cases and sensitivity analyses indicate the model's abilities and the algorithms’ effectiveness. The findings can introduce new insights for managers and engineers and a focal point for researchers to run new and extensive studies in this field. © 2021 Informa UK Limited, trading as Taylor & Francis Group.
International Journal of Services and Operations Management (17442370)39(2)pp. 262-282
The facility layout problem (FLP) is concerned with finding the optimal facility arrangement in the existing layout. A layout generation and its evaluation are often challenging and time consuming due to their inherent multiple objectives in nature and their data collection process. This paper aims to propose an integrated approach of fuzzy analytic hierarchy process (AHP), computer simulation and data envelopment analysis (DEA) for facility layout design improvement and optimisation. Computer simulation is used to determine quantitative measures. AHP is used to determine first, the weight of qualitative measures for layout alternatives and second, their qualitative measures. DEA is performed by employing total cost and wait time as the input variables, accessibility and flexibility as the output variables to evaluate different layouts. Then, the alternative layouts are ranked by solving the super-efficiency DEA model for the layouts. The results imply that the proposed methodology is more reliable compared to the existing approaches. © 2021 Inderscience Enterprises Ltd.. All rights reserved.
International Journal of Management Science and Engineering Management (17509653)16(1)pp. 43-57
The growing diversity in demand and the shorter life cycle of products necessitate integrating policies of design, production, and marketing to decide on which products, with which attributes should be designed and by which strategies should be supplied to the market. This necessity increases in the manufacturing of the Configurable Products Family (CPF) such as cars, laptops, cell phones. The existing decision-making models either do not deal with all the three policies or are not concerned with the main variables. This study aims to develop a profit maximization model to integrate policies for CPFs by optimizing the main variables: the product’s configuration, supply policy of components, price, and warranty lengths for product’s modules. A new demand function is developed for such decision-making as well. The model is mixed-integer nonlinear programming, so an adapted Particle Swarm Optimization (PSO) is applied to solve different numerical cases and perform several sensitivity analysis. The results depict significant changes in the company’s policy and profitability due to applying the model. The findings can introduce new insights for managers and engineers and a focal point for researchers to run further studies. © 2020 International Society of Management Science and Engineering Management.
International Journal of Electrical Power and Energy Systems (01420615)122
Purpose: In recent years, most organizations have been dealing with many economic, environmental and social problems. Iran's Electricity Distribution Network (EDN) with different supply stages involving generation, transmission, and distribution is a good case of a complex system engaging in sustainable activities; they must incorporate environmental and social concerns into traditional economic objectives. Assessing the sustainability of EDNs is complicate because it involves a variety of inputs, outputs and inter-related inputs/outputs at any stage of the network for which the importance of each stage may vary. Methodology: This paper proposes a new network data envelopment analysis (NDEA) model for assessing the sustainability of EDNs and their components. The proposed method has the following characteristics: All generation, transmission, and distribution stages, as well as the overall performance of the network, are evaluated in a unified framework; Undesirable outputs, re-work, and external inputs are considered in the model; Different weights for stages, determined by decision-makers, have been implemented to cause different effects on the network performance; The strengths and weaknesses of EDNs’ components are identified; The effect of each dimension of sustainability on the performance of EDNs’ components is investigated. Finding: The result of this study indicates that the Gharb EDN with an efficiency score of 0.8487 has the best performance and Mazandaran EDN with an efficiency score of 0.4667 has the worst performance. Based on the results, the paper proposes how to reduce inefficiencies in each stage of the network. © 2020 Elsevier Ltd
International Journal of Services and Operations Management (17442370)32(3)pp. 269-284
One of the important issues in the framework of supply chain is to determine the inventory control policy. In this regard, perishable goods are highly important due to their specific characteristics. In the present study, an inventory model for deteriorating items will be proposed considering constant demand, time value of money, and inflation. Deterioration begins immediately after the entrance of inventory into the warehouse. Delayed payment is allowable and degree of deterioration is fixed. Partially backlogged shortage is also considered and the purpose is to minimise total cost of the inventory system in a finite planning horizon. An exact algorithm was developed in this study for solving the problem and finally some numerical examples were presented. Sensitivity analysis was carried out on some of the important and basic parameters and the results were compared with the state where there is no partial backlogging. © Copyright 2019 Inderscience Enterprises Ltd.
International Journal of Engineering Systems Modelling and Simulation (17559766)7(4)pp. 256-261
This study aims at investigating the possible economical solutions to reduce the waiting times of the trucks that enter to factory to load the final products. To do so, the simulation of the system which is under study will be used. According to the recording time in the release and storage information of the factory's system, loading lines were the most time consuming sections, as a result this study focused on the existing lines. The study begins with timing the docks and different stations to access the system's factors which are under study. To simulate the system, ARENA 14 software was used. After validating the proposed model and confirming its validation, scenarios will be made in order to remove the obstacles while the trucks are loaded. Finally, some scenarios that decrease the trucks-wait time significantly were compared and prioritise among most economical solutions will be presented. © 2015 Inderscience Enterprises Ltd.
International Journal of Productivity and Quality Management (17466474)14(2)pp. 166-178
In today's competitive market, companies are trying to create distribution centres in different areas to attract more market. Given that the rival companies in that areas have a share of market, it will be important to establish these centres in different locations. The purpose of this article, is to get more distribution centres to attract new retailers, despite the competitive nature of the market, therefore a mathematical model, with two objective functions of maximising the market capture and the other minimising the sum of the cost of waiting and the travel time or distance of customers, the fixed purchasing costs and ordering costs is presented. Finally, objective functions of the considered model became an objective function using goal programming, Due to the complexity of the model and the lack of accurate and appropriate algorithms to solve them, using meta-heuristic algorithms such as tabu search algorithm, suitable locations for these centres is obtained. Copyright © 2014 Inderscience Enterprises Ltd.
As we know, in hospitals, the demand for drugs is unclear and change seasonal frequently. In medicine Providing a high level of service is needed. When there is a shortage in the local warehouse and we need to emergency deliver, emergency ordering is very costly and can be dangerous for the patient. Thus to minimum number of emergency orders and how much medication is needed for each location for each day is important. In fact, we seek to protect decisions for the pharmaceutical supply chain and find optimal variables inventory models. The physical size of the area should be considered as a limitation. When the inventory level is less than the order point, ordering is done automatically. Order point is the difference between high level of order and available inventory in time of the order. For each drug, separately, may choose the order level, and proved its value and also reduction of the workload (rework daily) and reduction of the cost of ordering and reduction of maintenance costs also should be considered that all of this, requires a management information system that is able to provide comprehensive information to the user. © 2014 IEEE.
Education, Business and Society: Contemporary Middle Eastern Issues (17537991)7(1)pp. 57-74
Purpose: The purpose of this study is to identify and rank the effective factors on customer values from the perspective of banking customers. Design/methodology/approach: This study is a practical and descriptive survey. In order to rank the factors affecting customer values, a fuzzy analytical hierarchical process has been used. The data were gathered through Delphi method and questionnaires. Findings: The results of this study indicate that the factors affecting customer values include costs, relational benefits, brand perceptions, and services quality. These factors influence customer values, respectively. The results also indicate that financial costs among costs, operational benefit among relational benefits, trust in employee behavior in customer brand perceptions, and finally confidence in service quality dimensions have the highest priority. Research limitations/implications: The proposed model and research findings will greatly help researchers and practitioners understand the factors influencing customer value using a fuzzy analytic hierarchy process (FAHP) in the banking industry. Originality/value: In this study, for the first time, factors influencing customer value are studied by using a FAHP in the banking industry. The use of this method in this study has a certain authenticity. © Emerald Group Publishing Limited.
Scientia Iranica (23453605)15(5)pp. 652-660
In this paper, a new approach to formulate a class of scheduling problems is introduced, which can be applied to many other discrete problems with complicated structures. The concept of graph circular coloring is applied to develop a model for the special case of an open shop scheduling problem. In this problem, there are some independent jobs to be processed in a shop with dedicated renewable resources. Each job consists of several tasks with no precedence restriction. Each task is processed without preemption. The processing time of the tasks is given. Processing each task requires using some multiple specified types of resource, while no more than one task can use each resource, simultaneously. Some tasks can be shared by more than one job and the process may be repeated more than once. The objective is to develop a schedule which yields the minimal makespan length of all jobs, as well as the number of cycles. The model is first developed for cases when the processing time of each task is one unit and, then, it is generalized by relaxing this restriction. In both cases, a circular coloring formulation is shown in comparison with traditional formulation (single process execution) results in an improved makespan and also the required information regarding the optimum number of cycles to repeat the process. © Sharif University of Technology, October 2008.
Afshani, P.,
Ghandehari, M.,
Ghandehari, M.,
Hatami h., H.,
Tusserkani, R.,
Zhu, X. Journal of Graph Theory (03649024)49(4)pp. 325-335
This paper proves that if G is a graph (parallel edges allowed) of maximum degree 3, then χc′(G) ≤ 11/3 provided that G does not contain H1 or H2 as a subgraph, where H1 and H2 are obtained by subdividing one edge of K23 (the graph with three parallel edges between two vertices) and K4, respectively. As χc′(H1) = χ c′(H2) = 4, our result implies that there is no graph G with 11/3 < χc′(G) < 4. It also implies that if G is a 2-edge connected cubic graph, then χc′(G) ≤ 11/3. © 2005 Wiley Periodicals, inc.
Discrete Mathematics (0012365X)293(1-3)pp. 121-127
A critical set in an n×n array is a set C of given entries, such that there exists a unique extension of C to an n×n Latin square and no proper subset of C has this property. For a Latin square L, scs(L) denotes the size of the smallest critical set of L, and scs(n) is the minimum of scs(L) over all Latin squares L of order n. We find an upper bound for the number of partial Latin squares of size k and prove thatn2-(e+o(1))n10/6≤maxscs(L)≤n2- π2n9/6.This improves on a result of Cavenagh (Ph.D. Thesis, The University of Queensland, 2003) and disproves one of his conjectures. Also it improves the previously known lower bound for the size of the largest critical set of any Latin square of order n. © 2005 Elsevier B.V. All rights reserved.
Linear Algebra and Its Applications (00243795)390(1-3)pp. 345-355
Let R be a non-commutative ring. The commuting graph of R denoted by Λ (R), is a graph with vertex set R \ Z(R), and two distinct vertices a and b are adjacent if ab = ba. In this paper we investigate some properties of Λ(R), whenever R is a finite semisimple ring. For any finite field F, we obtain minimum degree, maximum degree and clique number of Λ(M n (F)). Also it is shown that for any two finite semisimple rings R and S, if Λ(R) ≃ Λ(S), then there are commutative semisimple rings R1 and S1 and semisimple ring T such that R ≃T × R1, S ≃ T × S1 and |R1| = |S1|. © 2004 Elsevier Inc. All rights reserved.
