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European Journal of Industrial Engineering

European Journal of Industrial Engineering (EJIE)

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European J. of Industrial Engineering (24 papers in press)

Regular Issues

  • The impact of online sales in centralized and decentralized dual-channel supply chains   Order a copy of this article
    by Subrata Saha 
    Abstract: This paper studies a supply chain structure featuring two different types of distribution channels through which manufacturers sell products. The centralised and decentralised distribution channels considered in this study are affected by online sales outside the structured channels. In the centralised distribution channel, two retail stores located in geographically distinct markets are operated by a single owner. In the decentralised distribution channel, two retailers independently operate two retail stores. In the non-cooperative scenario, the manufacturer always prefers the decentralised distribution channel irrespective of whether an online channel is used. To achieve channel coordination, a revenue-sharing contract is applied, but it can be used to coordinate only the decentralised distribution system. Therefore, a modified revenue-sharing contract is proposed to coordinate the centralised distribution system. The analytical study reveals that without coordination among the channel members, the manufacturer always earns maximum profit in decentralised distribution systems. However, if the supply chain is coordinated, then the manufacturer receives more benefits from using the centralised distribution systems under certain conditions. Propositions are presented to describe the characteristics of distribution structures, and to provide meaningful management guidelines for coordinating them. Extensive numerical investigations are also presented.
    Keywords: Supply chain management; Dual-channel supply chain; Revenue sharing contract; Pricing strategy; Stackelberg.
    DOI: 10.1504/EJIE.2018.10011153
  • A decision-support model for dock and transport management after inbound logistics disruptions in the automotive sector   Order a copy of this article
    by Mohammadtaghi Falsafi, Davide Masera, Julien Mascolo, Rosanna Fornasiero 
    Abstract: One of the major disruptions in automotive supply chain is related to the on-time arrival of components from suppliers to assembly plants. In this paper, we develop an operative decision-support model to avoid ripple effect of these disruptions on production scheduling. In particular, based on strategies for truck-dock re-assignment and transport mode selection, the model is applied to a case study at Fiat Chrysler Automobiles (FCA). Moreover, the paper elaborates on the resilience and robustness of the supply chain in dealing with vulnerabilities in different phases of decision-making. The model allows supply chain managers to efficiently organise the transport modes of delayed orders, the in-plant material handling equipment, the arrival of trucks in the parking lot, and the use of inbound docks. [Submitted: 10 January 2021; Accepted: 5 April 2021]
    Keywords: disruption management; automotive sector; inbound logistics; dock management; transport management; supply chain resilience; truck-dock rescheduling; mixed-integer linear programming; MILP.
    DOI: 10.1504/EJIE.2022.10039350
  • Heuristic Procedure for Bi-capacitated Multiple-trip Vehicle Routing Problem   Order a copy of this article
    by Tarit Rattanamanee, Suebsak Nanthavanij 
    Abstract: The multiple-trip vehicle routing problem with physical workload (MTVRP-WL) or bi-capacitated MTVRP is intended to find an optimal number of delivery trucks and their travel routes to serve a set of customers having constant load demands within a given time limit. Delivery workers who are pre-assigned to trucks must manually unload goods at customer locations. Both trucks and workers are heterogeneous in terms of the load capacity and working energy capacity, respectively. Initially, the random nearest neighbourhood search technique is employed to generate an initial feasible solution. Then, the solution is improved using two local search operators, namely, greedy swap and 2-opt. The improvement algorithms are repeated for a number of iterations until no further improvement is obtained. From a computation experiment, the heuristic procedure is found to be efficient since it can obtain near-optimal MTVRP solutions in reasonable computation time. [Submitted: 5 November 2020; Accepted: 7 April 2021]
    Keywords: multiple-trip vehicle routing problem; bi-capacitated problem; heuristic algorithm; local search; physical workload; intra-city logistics.
    DOI: 10.1504/EJIE.2022.10039898
  • Supply chain optimal ordering policy under two-level trade credit with default risk   Order a copy of this article
    by Chengfeng Wu, Qiuhong Zhao, Chunfeng Xu 
    Abstract: The paper assumes that the manufacturer offers the wholesaler trade credit, and the wholesaler provides the retailer with trade credit in a three-echelon supply chain. First, we formulate the mathematical models that include the time value of capital and the partial default risk for the three members, respectively. Second, we derive the existence and uniqueness conditions of the optimal lot-size or production quantity for the members under decentralised replenishment policy. Finally, we present the sensitivity analysis of the optimal solution with respect to the parameters to provide managerial insights. The results show that the larger standard deviation of the demand, the more effective trade credit as the settlement method. The key contribution of the paper is that we present an ordering model that optimises lot sizes with two-level trade credit and investigate the transmission effect of default credit risk in a three-echelon supply chain under an uncertain market environment. [Submitted: 23 September 2020; Accepted: 8 April 2021]
    Keywords: supply chain; two-level trade credit; default risk; newsvendor model.
    DOI: 10.1504/EJIE.2022.10039901
  • Joint ordering policy for a conditional trade credit model with two retailers   Order a copy of this article
    by Zhen Zhang, Song-Tao Zhang, Ming-Shi Yue 
    Abstract: This paper focuses on the cooperation mechanism between two retailers. To reduce the average processing cost, the supplier usually sets a threshold for trade credit to stimulate retailers’ orders. Retailers can enjoy permissible delay in payments only when their order quantities are more than or equal to the given threshold. However, considering the diversity of retailers, the motivation effect of the threshold is limited. To resolve the problem, the supplier can additionally provide its retailers with a joint-ordering policy under which they can make delayed payments as long as their total order quantity meets the required threshold. We provide a mutually acceptable order-allocation scheme for two retailers, and determine the optimal payment methods for them. In addition, an optimal threshold is identified for the supplier to maximise the total order quantity of retailers. Based on this, some managerial insights are obtained. [Submitted 27 February 2020; Accepted 8 April 2021]
    Keywords: inventory; economic order quantity; EOQ; supply chain management; conditional trade credit; joint-ordering policy; cooperation mechanism; non-cooperative game; tacit bargaining.
    DOI: 10.1504/EJIE.2022.10039903
  • Optimization of a sustainable fuzzy EPQ inventory model using sextic equation   Order a copy of this article
    by Ganesan Subburaj, R. Uthayakumar 
    Abstract: We develop a fuzzy EPQ inventory model to achieve sustainability and profit maximisation. Cost measures are included at every stage of the production and inventory process to handle carbon emissions safely. Fuzzy number representation of the input parameters helps to accommodate uncertainties in the inventory decision-making process. The fuzzy net profit function’s ambiguity level determines the degree of uncertainty in the net profit. Descartes’ rule of signs is used in a sextic equation to establish a solution to the optimal length of the production run. The numerical results show that increasing ambiguity in the fuzzy profit function will decrease the net profit. Accuracy in predicting production cost, setup cost, and annual demand is essential as the net profit is more sensitive to these parameters. A multivariate regression equation is fitted to estimate a possible crisp net profit from the corresponding fuzzy net profit for given demand and production rates.
    Keywords: sustainability; EPQ inventory; trapezoidal fuzzy number; Descartes’ rule of signs.
    DOI: 10.1504/EJIE.2022.10040121
  • An Economic Order Quantity Model for Pareto Distribution Deterioration with Linear Demand under Linearly Time-Dependent Shortages   Order a copy of this article
    by Sindhuja. S, P. Arathi 
    Abstract: The inventory models for deteriorating items aim to reduce the total cost under normal market conditions. This paper focuses on the possible effects of minimising total cost by developing an economic order quantity (EOQ) model, where the deterioration is considered as Pareto distribution with linear demand. This model is applicable for vegetable vendors to make inventory decisions in the inventory system under the influence of optimal values. The linear demand and shortage of cost are also taken into consideration. To illustrate the proposed EOQ model, numerical examples and corresponding sensitivity analysis on the parameters A, c, d, pc, h, s, ? and ? are discussed and compared with the existing models. The result of the model developed in this paper is based on the deterioration leading to significant effects of the Pareto distribution deterioration variables ? and ? on the
    Keywords: economic order quantity; EOQ; Pareto distribution; deterioration; linear demand; shortage.
    DOI: 10.1504/EJIE.2022.10040122
  • An original approach to assess robustness of Road Freight Transport plannings based on a Dynamic Risk Identification   Order a copy of this article
    by Antoine CLEMENT, Didier Gourc, Daouda Kamissoko, François Marmier 
    Abstract: The road freight transport sector contributes significantly to the delivery of goods. Today, more than 90% of goods are conveyed using the road transport mode. In the same time, customers requirements become more and more numerous and accurate, which increases the complexity of planner work. The aim of this work is to propose to planners robustness indicators measuring the chance the planned tour could respect the requirements. Based on a planning system giving several feasible daily schedules, our approach allows to dynamically identify the risks that could impact each planning and then simulate the influence of those risks on the plans’ activities to assess robustness indicators. They are composed of an indicator measuring the probability to respect the customers’ requirements and two actionable data. These actionable data give to planners information on levers he could use to increase the robustness of the plan. [Submitted: 11 September 2020; Accepted: 27 April 2021]
    Keywords: risk identification; robustness; decision making; danger; daily schedule; road freight transport.
    DOI: 10.1504/EJIE.2022.10040419
  • New approach for quality function deployment with an extended alternative queuing method under linguistic Pythagorean fuzzy environment   Order a copy of this article
    by Ye-Jia Ping, Ran LIu, Ze-Ling Wang, Hu Chen Liu 
    Abstract: As a customer-driven tool to support the development of new products or services, quality function deployment (QFD) is able to transform customer requirements (CRs) into suitable engineering characteristics (ECs) to maximise the customer satisfaction. However, the conventional QFD method has some weaknesses limiting its effectiveness in the real applications. In this study, a new QFD approach based on linguistic Pythagorean fuzzy sets (LPFSs) and alternative queuing method (AQM) is constructed to enhance the performance of the traditional QFD. First, we express the assessments from experts on the relationships between CRs and ECs using the LPFSs. Second, we apply an extended AQM to determine the importance prioritisation of ECs. Additionally, a consensus reaching algorithm is adopted to dynamically determine the relative weights of experts considering their inconsistent judgements. An illustrative application of 5G smartphone development is conducted to demonstrate the feasibility and ef?ciency of our proposed QFD approach. Through the empirical case with a comparative analysis, the proposed approach is proved to be useful and practical for capturing experts’ opinions and prioritising ECs in QFD. [Submitted: 19 March 2020; Accepted: 11 April 2021]
    Keywords: quality function deployment; QFD; linguistic Pythagorean fuzzy set; LPFS; alternative queuing method; AQM; consensus reaching method; product development.
    DOI: 10.1504/EJIE.2022.10040422
  • Scenario-based stochastic shelter location-allocation problem with vulnerabilities for disaster relief network design   Order a copy of this article
    by Sweety Hansuwa, Usha Mohan, Viswanath Kumar Ganesan 
    Abstract: We formulate the shelter location-allocation problem considering the vulnerability of the demand locations and their network connectivities with the shelter locations for disaster management’s preparedness and response phase. We propose a scenario-based stochastic model that assigns the set of candidate locations evaluating operational, budgetary limitations, and service level expectations. The solution presents an evacuee-allocation plan considering the best collection of less vulnerable network connectivities between the demand areas and the shelter locations. We present a linear relaxation heuristic and compare the heuristic performance with the scenario-based formulation solved using CPLEX 12.8 optimisation solver for various problem sizes. We finally apply and solve the problem using real-life case data obtained during the major flooding event in and around the Chennai Metropolitan Development Area during 2015 to present our model’s applicability and emergency response requirements. [Submitted: 12 November 2020; Accepted: 19 April 2021]
    Keywords: disaster management; shelter location-allocation; stochastic programming; linear relaxation heuristic.
    DOI: 10.1504/EJIE.2022.10040737
  • An empirical analysis of the effect of customizing project management tools and techniques on industrial SMEs project success   Order a copy of this article
    by Eduardo Garcia-Escribano, Adolfo Lopez-Paredes, Javier Pajares 
    Abstract: Project managers have access to many tools and techniques to plan, monitor, and control their projects. However, not all of these project management tools and techniques (PMTT) are suited to the management of projects in all contexts and they may need to be customised or adjusted from the standard methodologies. The paper presents a comprehensive study with a duration of almost three years that used several research methods to answer the research questions posed. The study was made in 35 small and medium enterprises (SMEs), involving 94 projects in total and 54 project managers, focused on the manufacturing, healthcare, and telecommunications sectors. Although the results cannot be generalised, it is an interesting contribution relating to the tailoring of PMTT in SMEs and its correlation with a set of key performance indicators (KPIs) that measure project management performance.
    Keywords: empirical analysis; project management tools and techniques; PMTT; project success; project management standard methodologies; project monitoring; industrial SMEs.
    DOI: 10.1504/EJIE.2022.10041622
  • An improved AHP approach to select appropriate location sites for infectious medical waste disposal companies   Order a copy of this article
    by Hela Moalla Frikha, Frikha Ahmed 
    Abstract: Nowadays, infectious healthcare waste management has become a challenge task for the municipal authorities especially in developing countries including Tunisia, which considers this concern as one of the environmental priorities. Since these wastes have resistant impacts on public health and the deleterious effects on the environment, government authorities have deployed efforts to improve healthcare waste management. Locating infectious healthcare disposal firms is a sophisticated multi-criteria decision-making problem, which requires a compromise solution chosen according to conflicting criteria. This paper addresses the use of a modified analytic hierarchy process approach to select objectively the best sites for installing infectious healthcare waste disposal firms in Tunisia. A number of criteria and their sub-criteria are considered, several locations are evaluated, and the most appropriate ones are selected. Moreover, using expert choice software, sensitivity analysis is performed to show how sensitive the results are to the removal of one or more criteria. [Submitted: 21 January 2021; Accepted: 27 June 2021]
    Keywords: decision analysis; multiple criteria decision aid; waste disposal firm; infectious healthcare waste management; location problem; analytic hierarchy process.
    DOI: 10.1504/EJIE.2022.10041647
  • An efficient mat-heuristic algorithm for the dynamic disassembly assembly routing problem with returns   Order a copy of this article
    by Sana Frifita, Hasan Murat Afsar, Faicel Hnaien 
    Abstract: We study a static and dynamic disassembly assembly routing problem with returns (2D-ARP-R). The problem presents the case where a set of disassembled components and raw materials are converted into a final product. By regrouping production and routing decisions, it is possible to synchronise different activities (assembly, disassembly, inventory management, and vehicle routing) and build a global optimal solution. A mixed integer linear programming (MILP) is presented to solve this new variant. A mat-heuristic based on integer programming and variable neighborhood search algorithm (VNS) is also developed to solve the larger size instances. Numerical results show that the mat-heuristic approach improves the upper bounds obtained by CPLEX in a much shorter time, in most cases. We also evaluate the benefits of coordination of the production and routing decisions within the same optimisation model. This benefit can reach up to 117.38% compared to the hierarchical approach. [Submitted: 4 April 2020; Accepted: 27 June 2021].
    Keywords: supply chain management; assembly routing problem; ARP; disassembly problem; returns; mat-heuristic.
    DOI: 10.1504/EJIE.2022.10042377
  • Task dispatching in reconfigurable seru production systems to minimize total earliness and tardiness   Order a copy of this article
    by Jie Lian, ChenGuang Liu, Wenjuan Li, Juning Su, Hongquan Xue 
    Abstract: Owing to movable workstations, light equipment and multi-skilled workers, serus can be constructed, modified and dismantled rapidly. Taking over such an advantage, serus can be reconfigured in response to frequent changes in product types. The issue is how to arrange the configuration of seru with the tasks assigned to it. To this end, we focus on solving the task dispatching, product sequencing and seru reconfiguration problems simultaneously. A nonlinear mathematical model with objective of minimising the total earliness and tardiness is formulated. In order to verify the proposed model, small-size numerical examples are solved by Lingo. A genetic algorithm is developed due to its NP-hardness, and the algorithm is tested by numerical examples in different sizes. Based on the computational results, the performance of seru production systems and assembly lines is compared, and the impact of parameters on system performance is analysed. [Submitted 6 January 2020; Accepted 4 April 2021]
    Keywords: seru production; cell loading; seru reconfiguration; product sequencing; genetic algorithm.
    DOI: 10.1504/EJIE.2022.10042457
  • A Novel Two-Phase Algorithm for a Centralized Production Planning Problem by Symmetric Weighted DEA Approach: A Case Study in Energy Efficiency   Order a copy of this article
    by Elham Shadkam 
    Abstract: This paper proposes a novel two-phase algorithm for a centralised production planning problem that covers both long-term and mid-term planning simultaneously. Mid-term decisions (first phase) include determining the amount of new inputs and outputs of units in the next production period and long-term decisions (second phase) are related to planning to create a new efficient production unit. The first phase includes a data envelopment analysis approach with symmetric weights through the penalty function. The second phase includes combining data envelopment analysis and response surface methods. In order to evaluate the proposed method, the National Iranian Gas Company is considered as a real case problem. The results show the superiority of the algorithm in both phases over similar methods. The main advantage of the first phase is the realistic production plan. Also, the main advantage of the second phase is optimising the response surface functions and maximising the efficiency of the unit at the same time using one model.
    Keywords: production planning; symmetric weighted approach; data envelopment analysis; DEA; response surface method; gas company.
    DOI: 10.1504/EJIE.2022.10043239
  • Simultaneous Remanufacturing and Government Incentives in Remanufacturing Systems   Order a copy of this article
    by Mehmet ALEGOZ 
    Abstract: Remanufacturing has been receiving a growing attention in both academia and industry due to its economic and environmental benefits. This study investigates the effects of simultaneous remanufacturing, i.e., the effects of entrance of an actor to remanufacturing business when there is already one actor making remanufacturing. To this end, three remanufacturing systems are considered as only the manufacturer remanufactures (case 1), only the retailer remanufactures (case 2) and both the manufacturer and the retailer simultaneously remanufacture (case 3) the used products. Stackelberg Game models are proposed for each of these cases and the performances of the actors are compared. The role of the government in remanufacturing systems is also investigated and the question, to whom should the government provide incentives in order to maximise the remanufactured product quantity, is discussed. Computational results bring various managerial insights regarding the simultaneous remanufacturing decisions of the actors and the role of the government. [Submitted: 1 May 2021; Accepted: 4 October 2021]
    Keywords: remanufacturing; competition; government incentive; closed-loop supply chain.
    DOI: 10.1504/EJIE.2022.10043396
  • The Charging Infrastructure Design Problem with Electric Taxi Demand Prediction Using Convolutional LSTM   Order a copy of this article
    by Seong Wook Hwang, Sunghoon Lim 
    Abstract: The authors present a charging infrastructure design problem with electric taxi demand prediction. Due to environmental concerns, electric vehicle adoption has significantly increased in the transportation sector. However, the use of electric vehicles is not highly commercialised in the taxi industry, because the immature charging network and frequent charging decrease taxi revenue efficiency. Therefore, charging infrastructure needs to be built in urban areas in consideration of operational requirements of the taxi industry. The authors first design a convolutional long short-term memory model that predicts taxi demand, along with hotspots. Then, based on the predicted taxi demand in hotspots, a mixed integer linear programming model is proposed to optimise the location of recharging stations to minimise the cost of locating stations and charging service. Also, we propose a heuristic algorithm to solve realistic and practical problems. Lastly, a case study is presented to validate the proposed research. [Submitted: 28 April 2021; Accepted: 5 September 2021]
    Keywords: OR in service industries; transportation; heuristics; machine learning; artificial intelligence.
    DOI: 10.1504/EJIE.2022.10043497
  • Effects of variable setup cost, reliability, and production costs under controlled carbon emission in a reliable production system   Order a copy of this article
    by Ilkyeong Moon, Won-Young Yun, Biswajit Sarkar 
    Abstract: Although important for production industries to reach fully sustainable manufacturing processes, those implementing production systems face challenges in reaching this reliability goal. In this direction, a production system is modelled through a basic economic-production paradigm under carbon emissions with a storage constraint and demand-dependent unit production cost. More reliable production houses produce fewer defective products than the unreliable production system. As the model contains a power-function, a geometric programming procedure is employed to obtain a quasi-closed form of the optimal solution. A numerical example based on data from the literature and a case study based on industry data, are provided to demonstrate geometric programming as a valuable analytical tool to resolve this type of problem for a production system under carbon emissions. Finally, a sensitivity analysis and graphical illustration are provided to illustrate the model. Numerical results show that the production system becomes completely reliable when the recommended model is used. [Submitted: 18 May 2019; Accepted: 8 March 2021]
    Keywords: manufacturing systems; production design; geometric programming; inventory; variable production cost.
    DOI: 10.1504/EJIE.2022.10043835
  • Solving airline crew pairing problems through constraint partitioning   Order a copy of this article
    by Maryam Radman, Kourosh Eshghi 
    Abstract: In this paper, a decomposition technique based on constraint partitioning is developed to solve the crew pairing problem (CPP) which has an overriding importance in the airline industry as it determines the crew cost. The method is based on the observation that in large-scale problems the constraints can be partitioned to some sub-problems which involve special subsets of variables. The resultant structure is called the
    Keywords: crew pairing problems; CPPs; constraint partitioning; decomposition technique; sub-problem; airline industry.
    DOI: 10.1504/EJIE.2023.10044607
  • Waiting time distribution in single-channel deterministic flow lines with discrete inter-arrival time distributions   Order a copy of this article
    by Woo-sung Kim, Kyungsu Park 
    Abstract: Although previous studies proved that deterministic flow lines can be analysed separately by an exact decomposition method called a channel method and that the delay an item experiences in each machine possesses a Markovian property, the exact performance measures for the system with general arrival process cannot be obtained due to the lack of the results on relevant GI/D/1 queue. The solution obtained only for the system with specific arrival patterns such as geometric distribution or JIT arrivals considering setups. In this paper, exact decomposition methods are investigated through the systems consisting of one channel. Assuming general and discrete inter-arrival times, we introduce a procedure to calculate the equilibrium probabilities for waiting time distributions. It is demonstrated that probabilities can be computed by a matrix analytic method and recursions based on the decomposition methods. Inspired by the steel product manufacturing process, two-stage conveyor belt systems are analysed as an application. [Received: 28 July 2020; Accepted: 1 March 2021]
    Keywords: flow line model; stochastic modelling; Markov chain model; steel manufacturing system; tandem queue.
    DOI: 10.1504/EJIE.2022.10039905
  • Inventory control for the closed-loop supply chain with technological progress and planned shortages   Order a copy of this article
    by Shih-Pin Chen, Yu-Min Lin 
    Abstract: The impact of Industry 4.0 has received much attention in academic and practice fields. Therefore, understanding the effects of technological progress in production on closed-loop supply chain (CLSC) inventory management is critical. In view of profit efficiency, this paper investigates the effects of technological progress in production on inventory policies in a CLSC considering planned shortages. A CLSC production-inventory model is proposed to jointly determine sale and collection prices and production time points. The representative numerical results show that technological progress in manufacturing inconsistently has a positive impact on the NPU because the total quantity produced and cycle length vary. The impact of technological progress may be greater in the manufacturing process than in the remanufacturing process. The results can aid production managers in finding optimal production-inventory strategies considering technological progress and planned shortages. Additionally, the results provide useful information regarding the impact of technological progress in selecting investment targets. [Received: 5 August 2020; Accepted: 16 March 2021]
    Keywords: inventory; technological progress; remanufacturing; sequential quadratic programming; supply chain management; learning effects.
    DOI: 10.1504/EJIE.2022.10040426
  • A mathematical model for the optimal robust design of cause selecting control charts   Order a copy of this article
    by Salih O. Duffuaa, Ahmed M. Ghaithan, Ahmed M. Attia 
    Abstract: Cause selecting charts (CSC) are statistical control-charts for monitoring multiple sequential processes; in contrast, Shewhart control-charts are useful for monitoring independent processes. The economic-statistical design of CSC involves the selection of the optimal design parameters that include the width of the chart, sample size, and sampling interval. The application of economic-statistical criteria is a well-established and active research field. However, these design approaches may not be reliable for a dynamic production environment due to the uncertainty associated with the values of the model parameters. The purpose of this paper is to develop a robust economic-statistical model for the design of CSC. The model is intended to minimise the risk associated with the incidence of different scenarios in a real production environment. Through the use of examples and sensitivity analysis, it is demonstrated that the model provides design parameters that are more sensitive to shifts, protect against the occurrence of other scenarios, and results in charts with a higher power. [Received: 21 July 2018; Accepted: 24 March 2021]
    Keywords: quality; cause selecting chart; CSC; control charts; robust design; dependent processes.
    DOI: 10.1504/EJIE.2022.10040836
  • Synthetic control chart with curtailment for monitoring shifts in fraction non-conforming   Order a copy of this article
    by Salah Haridy, Nger Ling Chong, Michael B.C. Khoo, Mohammad Shamsuzzaman, Philippe Castagliola 
    Abstract: The integration of the curtailment method with control charts considerably improves the detection speed by signalling an out-of-control condition prior to the inspection of the whole sample. To date, few research works have focused on the incorporation of the curtailment method to improve the performance of control charts. Thus, this paper incorporates the curtailment approach with the synthetic chart to propose a synthetic with curtailment (Curt_Syn) control chart for detecting upward shifts in the fraction non-conforming, p. We compare the newly developed Curt_Syn chart with the synthetic, exponentially weighted moving average (EWMA), cumulative sum (CUSUM), EWMA with curtailment (Curt_EWMA), and CUSUM with curtailment (Curt_CUSUM) charts. From an overall perspective, the results reveal that the Curt_Syn chart surpasses the synthetic chart by 38% under various conditions. For all p shifts, the Curt_Syn chart outperforms the CUSUM and EWMA charts. When the p shift is large, the Curt_Syn chart is superior to the Curt_CUSUM and Curt_EWMA charts. To demonstrate the implementation of the Curt_Syn chart, an illustrative example is provided. [Received: 30 April 2019; Accepted: 7 April 2021]
    Keywords: control chart; synthetic chart; curtailment; fraction non-conforming; quality control; statistical process control; SPC; monitoring; attribute chart.
    DOI: 10.1504/EJIE.2022.10039904
  • Solving an integrated mathematical model for crew pairing and rostering problems by an ant colony optimisation algorithm   Order a copy of this article
    by Saeed Saemi, Alireza Rashidi Komijan, Reza Tavakkoli-Moghaddam, MohammadMohammad Fallah 
    Abstract: The crew pairing problem (CPP) and the crew rostering problem (CRP) are two sub-problems of a crew scheduling problem (CSP). Solving these problems based on a sequential approach may not yield the optimum solution. Therefore, the present study aims to consider the integrated CPP and CRP and present a new mathematical formulation. Due to its NP-hardness complexity, a meta-heuristic algorithm based on ant colony optimisation (ACO) is designed and used to solve the integrated problem and sequential approach (CRP followed by CPP) in some test problems extracted from a data set. The solutions provided by ACO for the integrated problem show 21.64% cost reduction in a reasonable time increase in comparison with those obtained by the sequential approach. Also, the ACO algorithm can provide solutions with a 2.96% average gap to the optimal solutions (by the exact method) for small-sized problems. Also, the proposed integrated approach leads to solutions with the best/optimal number of crew members to be assigned. The findings indicate that the proposed ACO has an efficient performance in solving the integrated problem. [Received: 20 May 2020; Accepted: 8 April 2021]
    Keywords: crew pairing and crew rostering; crew scheduling; inseparable flights; ant colony optimisation; ACO.
    DOI: 10.1504/EJIE.2022.10040418