This paper presents two models (classical and VMI-CS coordination) for a two-level closed-loop supply chain with a manufacturer and a retailer with a facility to remanufacture used items. The paper ...considers three critical environmental issues, which are the energy used in production (manufacturing and remanufacturing) processes, GHG emissions from production and transportation activities (subject to a penalty tax), and the number of times to remanufacture (recover) a used item. Numerical results show that the traditional optimization approach, which minimises the sum of inventory related costs, suggested less remanufacturing, fewer recovery times and more GHG emissions and energy usage; a result of operating at high production rates. The VMI-CS model was shown to be more economical than the classical model for a wide range of manufacturing rates, but not necessarily a more environmentally responsible choice. An extensive numerical analysis was conducted to enrich the discussion and to draw some managerial insights on how to make environmentally conscious decisions.
•Lot sizing in CLSC with GHG emissions and energy costs is considered.•Used items are remanufactured for a limited number of times.•VMI-CS policy was shown to be economical and, mostly, environmentally responsible.•Managerial insights are provided environmentally conscious decision-making.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Mathematical models of inventory typically include the three inventory associated costs of surplus, shortage and ordering. These classic inventory models are then analysed so as to choose inventory ...parameters that usually minimise the total cost of operating the inventory system being investigated.
Unfortunately, classic inventory models do not provide a meaningful basis for analysing many real and increasingly important practical inventory problems and situations. It is therefore not surprising that over recent years, several authors have discussed these issues in broad terms and suggested that a new paradigm needs to be developed.
This paper develops some specific aspects of this discussion. In particular, the paper identifies a range of inventory problems that are not covered appropriately by traditional inventory analysis. One of these is to design responsible inventory systems, i.e. systems that reflect the needs of the environment. The paper then examines the importance of inventory planning to the environment in greater detail. For example, packaging is important, not only because of its costs and the protection that it provides to the inventory items, but also because of its eventual effects on the environment in terms of the use of resources and potential landfill. For similar reasons, waste, which can result from poor inventory management, is highly important. The location of stores is important because location affects transport costs. Thus the influence of the secondary aspects of most inventory models; packaging, waste and location are important but, even more important are the inter-relations with the total system. In particular, the location of the manufacturing plants and the effect that inventory planning has on the logistics chain, potentially have considerable environmental implications. Inventory is part of a wider system.
However, until the cost charged for an activity reflects the true environmental cost of that activity, it is likely that decisions will be made on the basis of erroneous data. In that situation, we are faced with either determining the environmental cost of specific actions or to use environmental costs that are somewhat contrived; in which case it may be more sensible to use very different performance measures and models. The paper discusses these ideas and ways in which inventory policies may reassure us with our environmental concerns.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Order picking (OP) activities, essential to logistics operations, are laborious and time-intensive. Humans are central actors in the OP process and determine both OP effectiveness and efficiency. ...Many researchers have developed models for planning OP activities and increasing the efficiencies of such systems by suggesting different warehouse layouts, OP routes or storage assignments. These studies have, however, ignored workers' characteristics, or human factors, suggesting that they cannot be substantiated, which led to only partially realistic results. This paper proposes a conceptual framework for integrating human factors into planning models of OP activities and hypothesises that doing so improves the performance of an OP system and workers' welfare. The framework is based on a systematic literature review that synthesises findings documented in the OP and human factors literature. The results of the paper may assist researchers and practitioners in designing OP systems by developing planning models that help in enhancing performance and reducing long-term costs caused by work-related inefficiencies.
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BFBNIB, GIS, IJS, IZUM, KILJ, KISLJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
Vendor managed inventory (VMI) is an approach used by several companies to monitor and control stocks of their products. In this paper, we investigate how VMI with a Consignment Stock (CS) policy may ...exemplify a successful strategy for both buyers and suppliers. CS allows a vendor to stock some or its entire inventory using its buyers’ warehouses. This paper considers the problem of a single vendor with multiple buyers collaborating under VMI with a consignment stock policy. Collaboration between buyers is made possible by allowing transshipments from one buyer to another. Those transshipments pass through multiple redistribution hubs whose locations are determined by considering the inventory levels of buyers and shipment storage capacities between them. This paper shows that transshipments between buyers can be a tool for decreasing the total cost faced by both buyers and their suppliers. Numerical results are also presented to illustrate it and discuss its importance. The cost function is shown to be jointly convex in the shipment sizes between the buyers and them and the vendor under certain conditions, where a genetic algorithm is developed to find the number of shipments between the vendor and buyers.
•Considers a VMI-CS for a vendor-multibuyer system with cross-shipments.•A genetic algorithm is developed to solve the problem.•Cross-shipment between the buyers reduces the joint total cost.•Investment to increase warehouse and shipments capacities reduces costs further.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
It is imperative for contemporary businesses to proactively search for ways of continuously improving the performance of their supply chains. Supply chain coordination and integrated decision making ...across the supply chain among various supply chain partners are frequently employed towards this end. Such supply chain coordination strategies include the use of common cycle time, quantity discounts, optimal lot sizing, quality improvements and inspections, etc. An important issue lacking in the supply chain literature relates to the incorporation of such quintessential and omnipresent human factors as errors in quality inspections and production improvements due to learning. This paper provides a simple but integrated mathematical model for determining an optimal vendor–buyer inventory policy by accounting for quality inspection errors at the buyer’s end and learning in production at the vendor’s end. The objective is to minimize the joint annual cost incurred in the supply chain. A numerical example is presented to illustrate the application and the substance of the proposed model. We discuss how such integrated models can be used for justifying investments in such strategic and operational areas as relationship management, product design, process design, and personnel training. We also provide some very interesting and challenging future research directions.
► Used a conventional stocking policy to study a vendor–buyer supply chain. ► Incorporated two important human factors to a model in the literature. ► Learning in production brought in a substantial drop in the annual cost of the supply chain. ► Type I error has a more pronounced effect on the supply chain costs as compared to the Type II errors. ► This model can be used for justifying investments in relationship management, product/process design and workers’ training.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
This paper presents a joint economic lot size (JELS) model for coordinated inventory replenishment decisions under the vendor-managed inventory (VMI) with consignment stock (CS) agreement and an ...emission-trading scheme. The paper assumes a single product that flows along a two-level supply chain system, with a single vendor and a single buyer. The total cost of the system is the performance measure, which is the sum of the vendor's and the buyer's total costs. The total cost includes the set-up and order costs, inventory holding costs, greenhouse gases (GHG) emissions tax and penalty costs. A mathematical model is proposed to determine: (1) the vendor's production lot size quantity; (2) the number of shipments sent by the vendor to the buyer in a cycle; and (3) the production rate that minimises the total cost of the supply chain. Some numerical examples are carried out, as well as comparisons with the traditional JELS model for a classic two-level supply chain. Results show that the performance of the system is better when it is operated under a VMI with CS agreement, which is capable of reducing the traditional inventory holding costs and, for some values of given parameters, the GHG emissions tax and penalty costs.
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BFBNIB, GIS, IJS, IZUM, KILJ, KISLJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
An approach similar to Salameh and Jaber (2000) has been used in this paper to produce an optimal production/order quantity that takes care of imperfect processes. An imperfect inspection process ...(Raouf et al., 1983) is utilized to describe the defective proportion of the received lot. That is, the inspector may commit errors while screening. The probability of misclassification errors is assumed to be known. The inspection process would consist of three costs: (a) cost of inspection (b) cost of Type I errors and (c) cost of Type II errors. The defective items, classified by the inspector and the buyer would be salvaged as a single batch that is sold at a lower price. A mathematical model is developed to depict this scenario. Numerical examples are provided to illustrate the solution procedure.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
The purpose of this paper is to study the effects of various scenarios of delay-in-payments (a form of trade credit) by a buyer after receiving items, while including various costs such as fuel cost, ...the costs of carbon emissions from manufacturing and transportation activities, order cost, and setup cost in a two-echelon coordinated supply chain. The model developed optimizes the environmental and economic performance of a supply chain. The study presents a comparison of different scenarios through numerical examples and sensitivity analyses. The main contribution of this paper is the joint consideration of delays-in-payments, and the costs of transportation cost, and carbon emissions. The model has been tested with numerical examples, and sensitivity analyses. The findings showed that adopting delays-in-payments improves both environmental and economic performance of a supply chain. The analyses also showed that optimizing one of the parameters from the production rate, the length of delay-in-payments or the lot size provides the optimal solution for carbon emissions and the system cost of a supply chain. This flexibility makes the model easy to use by practitioners.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
•Develops novel MIPP model and heuristic to solve the large-scale instances in liner shipping.•Explores the blockage of the Suez Canal versus rerouting through the Cape of Good Hope.•Results show ...that adjusting vessel speed and/or skipping call-ports mitigates costly disruptions.•Examines temporary cargo storage and accounts for GHG increased from vessel speeding.•Conducts extensive computations to validate and analyze the model.
Disruptions often occur in liner shipping networks, and they are costly. When they occur, freight companies evaluate their effects on freightage in the pipeline and take the appropriate recovery actions by balancing customer service levels and increases in fuel consumption while accounting for environmental impact (greenhouse gas (GHG) emissions). The paper, therefore, develops an integrated mixed-integer programming problem (MIPP) that jointly minimizes the total voyage and transshipment costs and penalty charges for emitting GHG excess amounts beyond what is allowed. It does so by recovering a pre-established schedule of disrupted containerships. The solution to the MIPP suggests how to reconfigure the liner shipping network when skipping one or more call ports and determines the optimal velocity on assigned routes. The paper also develops and proposes a new and efficient algorithm based on the Crowd-Learning Particle Swarm Optimization (CLPSO) to solve this large-scale problem and shows the CLPSO to be superior to the potential ones in the literature. Computational experiments, based on data from a maritime shipping company, demonstrate the effectiveness of both the MIPP and CLPSO using several comparative metrics with suitable assumptions. The numerical results show that the developed MIPP has a potential application in practice.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
This paper proposes a probabilistic model for assessing corporate sustainability performance. The need for probabilistic approaches to sustainability measurement is on the rise. Existing approaches ...to measuring strong sustainability, which emphasize the non-substitutability of resources, overwhelmingly focus on the national- or regional-levels. Few “strong” sustainability models explicitly address performance at the company level. The model proposed in this paper is also unique in that it addresses situations where the variables used to measure performance are dependent on one another. Existing approaches focus on independent variables. The model is provided in a generalized form and offers a straightforward approach to assessing the sustainability performance of corporations. Also discussed in the paper are some managerial and academic implications of the model.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
