| 1. |
- Andriolo, Alessandro, et al.
(författare)
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A century of evolution from Harriss basic lot size model : Survey and research agenda
- 2014
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Ingår i: International Journal of Production Economics. - : Elsevier. - 0925-5273 .- 1873-7579. ; 155, s. 16-38
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Tidskriftsartikel (refereegranskat)abstract
- Determining the economic lot size has always represented one of the most important issues in production planning. This problem has long attracted the attention of researchers, and several models have been developed to meet requirements at minimum cost. In this paper we explore and discuss the evolution of these models during one hundred years of history, starting from the basic model developed by Harris in 1913, up to today. Following Harriss work, a number of researchers have devised extensions that incorporate additional considerations. The evolution of EOQ theory strongly reflects the development of industrial systems over the past century. Here we outline all the research areas faced in the past by conducting a holistic analysis of 219 selected journal papers and trying to give a comprehensive view of past work on the EOQ problem. Finally, a new research agenda is proposed and discussed.
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| 2. |
- Berling, Peter, et al.
(författare)
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Lead-time investigation and estimation in divergent supply chains
- 2014
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Ingår i: International Journal of Production Economics. - : Elsevier. - 0925-5273 .- 1873-7579. ; 157:SI, s. 177-189
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Tidskriftsartikel (refereegranskat)abstract
- This paper investigates the delay experienced by retailers in a distribution system due to shortages at the central warehouse. Simple formulae are developed to estimate the mean and variance of this delay. The formulae are based on replacing the stochastic lead-time demand with a stochastic demand rate, and they differ in how this demand rate is estimated. An extensive numerical study shows improved accuracy compared to existing methods with similar computational complexity. The numerical study also shows that the batch quantities and the service level have a large influence on the delay. Both the mean and variance of a retailer’s delay decrease with the service level and increase with the batch quantities used at the warehouse and at the retailer. No other variables seem to have a significant impact on the delay.
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| 3. |
- Bogataj, Marija, et al.
(författare)
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Efficient location of industrial activity cells in a global supply chain
- 2011
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Ingår i: International Journal of Production Economics. - : Elsevier. - 0925-5273 .- 1873-7579. ; 133:1, s. 243-250
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Tidskriftsartikel (refereegranskat)abstract
- Inefficient locations for production, distribution and reverse logistics plants will result in excess costs no matter how well material requirements planning (MRP), inventory control, distribution and information sharing decisions are optimized. In this paper we study ways in which aspect of activity cell location decisions can be analyzed within an extended MRP model. This model has previously been extended by including distribution and reverse logistics components in a compact form, presented in Grubbstrom et al. (2007). Our aim is to demonstrate the basic differences between an approach to location problems with MRP "under the same roof" as the global supply chain, in which transportation time delays and direct transportation costs have substantial influence. We discuss possibilities of how to present location aspects in the supply chain model obtained from combining input-output analysis and Laplace transforms in four sub-systems, namely manufacturing, distribution, consumption and reverse logistics, and show how the transportation costs and lead time influenced by the location of all these activities affect the resulting net present value (NPV). Our aim is to build a model supporting decisions concerning the structure of a supply chain as an alternative to a mixed integer programming formulation. The model developed is based on the use of continuous functions describing spatial distributions of cost and customer demand. Continuous functions are embedded in the MRP extension previously introduced in Grubbstrom et al. (2007). Location decisions influence (i) production costs, because timing influences the cost of activities involved in creating a product, cf. (Grubbstrom and Bogataj, submitted for publication), and (ii) logistics costs, which refer to the procurement and physical transmission of materials through the supply chain. In this current paper we wish to combine both of these aspects into a comprehensive model, where we show the interaction between the "space of flows" and the "space of places" as Giovanni Arrighi distinguishes one from the other in his book The Long Twentieth Century.
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| 4. |
- Bogataj, Marija, et al.
(författare)
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On the representation of timing for different structures within MRP theory
- 2012
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Ingår i: International Journal of Production Economics. - : Elsevier. - 0925-5273 .- 1873-7579. ; 140:2, s. 749-755
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Tidskriftsartikel (refereegranskat)abstract
- MRP Theory has been developed during the last 25 years for capturing processes concerning multi-level, multi-stage production-inventory systems in a compact way. Input-output analysis has been used to describe structures, and Laplace transforms to describe the timing relations. This theory has mainly dealt with assembly systems, in which each item has only one successor. The lead times for the assembly of an item have usually been constants and equal for all items entering a given successor. For such systems, the equations describing the flows of components may be written to include the generalised input matrix as the product of an input matrix containing needed amounts, and a diagonal lead time matrix with lead time operators along its main diagonal. less thanbrgreater than less thanbrgreater thanOn occasion, there has been a need to deviate from this representation enabling lead times to vary depending on which input item that is considered. This paper deals with how to represent lead times and similar output delays (in diverging, arborescent systems), when the assumption of equal times is relaxed, in order to retain the basic structure of the fundamental balance equations involved. The intention of this paper is to create a general taxonomy for the representation of timing in algebraic form for a variety of systems covering both assembly systems and arborescent systems (such as extraction, distribution and remanufacturing), as well as systems with mixed properties. For instance, this method may be used directly for the evaluation of investments in capacity or in the location of activities in a production network, or even in a global supply chain.
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| 5. |
- Bogataj, Marija, et al.
(författare)
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Transportation delays in reverse logistics
- 2013
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Ingår i: International Journal of Production Economics. - : Elsevier. - 0925-5273 .- 1873-7579. ; 143:2, s. 395-402
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Tidskriftsartikel (refereegranskat)abstract
- In this paper we extend and apply MRP theory towards reverse logistics including the considerations of transportation consequences. Our aim is to demonstrate the versatility obtained from using MRP theory when combining Input-Output Analysis and Laplace transforms. This enables an analysis of a supply chain including four sub-systems, namely manufacturing, distribution, consumption and reverse logistics, where the geographical distance between the activities play an important role. The main focus in this paper is on reverse logistics (recycling, remanufacturing). Especially we wish to model the evaluation of disposal and reverse activities far away from agglomerations, which often means an improved environment for nearby inhabitants. This is also illustrated in a numerical example. We use the Net Present Value as a measure of the economic performance. Our ambition is to show that supply chain sub-systems may accurately be described using input and output matrices collected together in corresponding matrices for the system as a whole. Activity levels in each sub-system govern the speed of the respective processes, and these activity levels, in general, will be considered as decision variables. We now analyse reverse logistics activities in which the flows of materials and goods are typically divergent (arborescent processes), similar to properties of the distribution sub-system, and recent results on the extensions of basic MRP theory introducing the concepts of output delays and the generalised output matrix are also introduced here, when modelling the reverse logistics sub-system.
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| 6. |
- Chen, Lujie, et al.
(författare)
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Manufacturing facility location and sustainability: A literature review and research agenda
- 2014
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Ingår i: International Journal of Production Economics. - : Elsevier BV. - 0925-5273 .- 1873-7579. ; 149, s. 154-163
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Tidskriftsartikel (refereegranskat)abstract
- The perspectives on the manufacturing footprint of global firms are widening from the economic aspects to also include the environmental and social aspects. Thus, sustainability is becoming an important issue for the location of manufacturing facilities. It is therefore timely to review the relevant aspects and dimensions in the extant literature to investigate the relationship between sustainability and facility location. In this paper, we aim to understand how sustainability aspects are included in decision-making concerning manufacturing facility locations and the role of location in evaluating manufacturing sustainability. We examine the literature streams on sustainability and facility location. A comprehensive search includes peer-reviewed literature from 1990 to 2011. We propose a literature classification scheme with respect to focal area and research methodology. The content analysis identifies the environmental, social and economic perspectives and factors affecting location decisions. We synthesize the findings into a framework for taking sustainability aspects into account in manufacturing facility location decision-making. We also propose a research agenda for further research on sustainable locations.
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| 7. |
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| 8. |
- Farvid, Mojtaba, 1975-, et al.
(författare)
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The discounted (R,Q) inventory model : The Shrewd Accountant's Heuristic
- 2014
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Ingår i: International Journal of Production Economics. - : Elsevier. - 0925-5273 .- 1873-7579. ; 149, s. 17-27
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Tidskriftsartikel (refereegranskat)abstract
- The discounted continuous-review (R,Q) inventory model with continuous and stochastic demand is investigated. New optimality conditions are derived, clarifying the difference to the average cost case, also graphically. Supported by depreciation theory, applied to the value of a setup, the results suggest an insightful and very precise approximation – The Shrewd Accountant’s Heuristic – based on a new average-cost model. It deepens and extends the work of Hadley (1964). Three examples are worked out in detail and the model is generalized to Poisson demand and to stochastic lead-times.
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| 9. |
- Figge, Frank, et al.
(författare)
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Is green and profitable sustainable? Assessing the trade-off between economic and environmental aspects
- 2012
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Ingår i: International Journal of Production Economics. - : Elsevier. - 0925-5273 .- 1873-7579. ; 140:1, s. 92-102
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Tidskriftsartikel (refereegranskat)abstract
- Businesses are more and more confronted with demands to play an active role to reduce environmental burdens effectively and to help to achieve environmental sustainability. We question the suitability of the green business case and argue that corporate environmental strategies need to aim at the creation of environmental value alongside economic value rather than the creation of economic value through environmental management. Three shortcomings of the green business case limit its usefulness to develop suitable corporate sustainability strategies. We contrast the green business case with an opportunity cost based approach for assessing the environmental performance of firms. Our argument is then applied to an integrated analysis of the financial, carbon and VOC-performance of 16 major car manufacturers worldwide to illustrate how companies respond to the twofold scarcity of economic capital and natural resources as well as the role of proactive technology choices in this context. Our analysis shows how firms can go beyond the standard green business case that ultimately limits environmental strategies to increasing capital efficiency. We argue that by applying the well established notion of opportunity costs to the assessment of environmental resources besides economic capital, companies can identify strategies that create economic and environmental value and help to maximise the contribution to sustainability rather than to economic capital efficiency alone.
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| 10. |
- Grubbström, Robert
(författare)
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Cumulative staircase considerations for dynamic lotsizing when backlogging is allowed
- 2014
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Ingår i: International Journal of Production Economics. - : Elsevier. - 0925-5273 .- 1873-7579. ; 157, s. 201-211
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Tidskriftsartikel (refereegranskat)abstract
- The dynamic lotsizing problem concerns the determination of optimal batch quantities, when given required amounts appear at discrete points in time. The standard formulation assumes that no shortages are allowed and that replenishments are made instantaneously.For the case when no shortage is allowed, previously it has been demonstrated that the inner-corner condition for an optimal production plan in continuous time reduces the number of possible replenishment times to a finite set of given points at which either a replenishment is made, or not. The problem is thus turned into choosing from a set of zero/one decisions with 2n−1 alternatives, of which at least one solution must be optimal, where n is the number of requirement events. Recently, the instantaneous replenishment assumption has been replaced by allowing for a finite production rate, which turned the inner-corner condition into a condition of tangency between the cumulative demand staircase and cumulative production.In this paper we investigate relationships between optimal cumulative production and cumulative demand, when backlogging is permitted. The production rate is assumed constant and cumulative production will then be a set of consecutive ramps. Cumulative demand is a given staircase function. The net present value (NPV) principle is applied, assuming a fixed setup cost for each ramp, a unit production cost for each item produced and a unit revenue for each item sold at the time it is delivered.Among other results, it is shown that optimal cumulative production necessarily intersects the demand staircase. Instead of having 2n−1 production staircases as candidates for optimality, there are 2n−1 production structures as candidates. These are made up of sequences of batches, of which the set of batches may be optimised individually. Also is shown that the NPV of each batch has a unique timing maximum and behaves initially in a concave way and ends as convex.Results for the average cost approach are obtained from a zeroth/first order approximation of the objective function (NPV).
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