| 1. |
- Al-Najjar, Basim, 1954-, et al.
(författare)
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Selecting the Most Efficient Maintenance Approach Using Fuzzy Multiple Criteria Decision Making
- 2003
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Ingår i: International Journal of Production Economics. - 0925-5273 .- 1873-7579. ; 84:1, s. 85-100
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Tidskriftsartikel (refereegranskat)abstract
- We assess the most popular maintenance approaches, i.e. strategies, policies, or philosophies, using a fuzzy multiple criteria decision making (MCDM) evaluation methodology. We illustrate with two examples how the suggested evaluation methodology identifies the most informative approach. Using the fuzzy MCDM, it would be possible to select in advance, the most informative (efficient) maintenance approach. Consequently, this leads to less planned replacements, and failures would be reduced to approximately zero and higher utilization of component life can be achieved. Thus, the maintenance department could contribute more to the business objectives throughout participating effectively in adding value to the production activities.
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| 2. |
- Aguilar Sommar, Ruth
(författare)
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Business process modelling : Review and framework
- 2004
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Ingår i: International Journal of Production Economics. - 0925-5273 .- 1873-7579. ; 90:2, s. 129-149
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Tidskriftsartikel (refereegranskat)abstract
- A business process is the combination of a set of activities within an enterprise with a structure describing their logical order and dependence whose objective is to produce a desired result. Business process modelling enables a common understanding and analysis of a business process. A process model can provide a comprehensive understanding of a process. An enterprise can be analysed and integrated through its business processes. Hence the importance of correctly modelling its business processes. Using the right model involves taking into account the purpose of the analysis and, knowledge of the available process modelling techniques and tools. The number of references on business modelling is huge, thus making it very time consuming to get an overview and understand many of the concepts and vocabulary involved. The primary concern of this paper is to make that job easier, i.e. review business process modelling literature and describe the main process modelling techniques. Also a framework for classifying business process-modelling techniques according to their purpose is proposed and discussed. © 2003 Elsevier B.V. All rights reserved.
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| 3. |
- Bengtsson, Jens
(författare)
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Manufacturing flexibility and real options : A review
- 2001
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Ingår i: International Journal of Production Economics. - 0925-5273 .- 1873-7579. ; 74:1-3, s. 213-224
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Forskningsöversikt (refereegranskat)abstract
- This paper considers manufacturing flexibility and real options from an industrial engineering/production management perspective. Real options papers are related to different types of manufacturing flexibility in order to show which types that are considered and in what way they are considered. Flexibility types not valued with real options and real options without any corresponding manufacturing flexibility type are identified and discussed. © 2001 Elsevier Science B.V. All rights reserved.
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| 4. |
- Bengtsson, Jens, 1973-, et al.
(författare)
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Valuation of product-mix flexibility using real options
- 2002
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Ingår i: International Journal of Production Economics. - 0925-5273 .- 1873-7579. ; 78:1, s. 13-28
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Tidskriftsartikel (refereegranskat)abstract
- Flexibility in manufacturing operations is becoming increasingly more important to industrial firms, due to e.g., increasing market demand volatility, internationalisation of markets and competition, and shorter product life cycles. Defining, measuring and evaluating manufacturing flexibility have not been straightforward - neither in theory nor in practice. The use of real options has shown to be an accessible approach for the valuation of certain types of flexibility. When using real options for capital budgeting purposes it is possible to take flexibility options into account in the valuation process. In this paper, we use real options to evaluate one specific type of manufacturing flexibility, i.e., product-mix flexibility. We provide both theoretical and practical perspectives, based on a real case. The main interest of the company under study is to evaluate product-mix flexibility with respect to capacity, set-ups, level of automation and multi-functionality of resources. The case involves multiple products and demand uncertainty, wherefore product demands are used as the underlying asset in the real options models. Thus, the contribution of this paper concerns the combination of real case, multiple products, capacity constraints, and set-up costs. The results of the analysis show that (i) the value of flexibility decreases when demand volatility increases, (ii) flexible resources add substantial value as compared to dedicated resources, and (iii) the flexibility value of marginal capacity decreases with increasing levels of capacity.
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| 5. |
- Grubbström, Robert W., et al.
(författare)
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A stochastic model of multi-level/multi-stage capacity-constrained production–inventory systems
- 2003
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Ingår i: International Journal of Production Economics. - 0925-5273 .- 1873-7579. ; 81-82, s. 483-494
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Tidskriftsartikel (refereegranskat)abstract
- A great deal of research has been done on capacity-constrained production–inventory systems, most of which concerns deterministic demand situations and single-product systems. In this paper we present a model of a multi-level capacity-constrained system when external demand is stochastic. Unlike the traditional total cost objective, adopted in the vast majority of capacity-constrained production–inventory models, the (expected) Net Present Value is here used as the objective function. Dynamic programming is chosen as the solution procedure. Numerical examples are given to explain the model and to illustrate features when changing available capacity.The Laplace transform together with input–output analysis are employed as tools to construct the model. This approach has been used in previous research to formulate a theoretical base for Material Requirements Planning (MRP) systems.The paper provides a further argument for the use of transforms in combination with matrix representations of product structures and capacity requirements, and it extends previous theory in the direction of capacity considerations combined with uncertainty in external demand. Dynamic programming is also shown to be a practical method for the multi-stage optimisation involved.The numerical examples further illustrate, for instance, the natural propensity for subordinate items to be lot sized in a more lumpy way than their parents, and also how the marginal benefit of capacity increments follows the law of diminishing returns. Also comparisons are made with solutions from the deterministic equivalence model, using average demand as a proxy.
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| 6. |
- Grubbström, Robert W., et al.
(författare)
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Igls 2000
- 2002
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Ingår i: International Journal of Production Economics. - 0925-5273 .- 1873-7579. ; 77:3, s. 189-190
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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| 7. |
- Grubbström, Robert W., 1941-, et al.
(författare)
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Modelling Rescheduling Activities in a Multi-Period Production-Inventory System
- 2000
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Ingår i: International Journal of Production Economics. - : Elsevier. - 0925-5273 .- 1873-7579. ; 68:2, s. 123-135
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Tidskriftsartikel (refereegranskat)abstract
- Decisions for planning production activities for multi-period production–inventory systems have been studied in a number of papers applying input–output analysis and the Laplace transform. The decisions have concerned activities spread out over time without having the opportunity to adjust future decisions when the external and/or internal circumstances change. In this paper, we extend the analysis to situations when rescheduling is possible. Firstly, different classes of causes justifying rescheduling activities are presented including periodic rescheduling and “net change”. Secondly, in terms of previously developed theory, we model the behaviour of a simple single-level production–inventory system for which its production plan may be modified at one point in the future.
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| 8. |
- Göthe-Lundgren, Maud, et al.
(författare)
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An optimization model for refinery production scheduling
- 2002
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Ingår i: International Journal of Production Economics. - Amsterdam, Netherlands : Elsevier. - 0925-5273 .- 1873-7579. ; 78:3, s. 255-270
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Tidskriftsartikel (refereegranskat)abstract
- In this paper we describe a production planning and scheduling problem in an oil refinery company. The problem concerns the planning and the utilization of a production process consisting of one distillation unit and two hydro-treatment units. In the process crude oil is transformed to bitumen and naphthenic special oils. The aim of the scheduling is to decide which mode of operation to use in each processing unit at each point in time, in order to satisfy the demand while minimizing the production cost and taking storage capacities into account. The production cost includes costs for changing mode and for holding inventory. We formulate a mixed integer linear programming model for the scheduling problem. The model can be regarded as a generalized lot-sizing problem, where inventory capacities are considered and more than one product is obtained for some modes of operation. A number of modifications and extensions of the model are also discussed. It is shown how the optimization model can be used as a viable tool for supporting production planning and scheduling at the refinery, and that it is possible to analyze scheduling scenarios of realistic sizes. It is also shown that the model can support shipment planning and strategic decisions concerning new products and investments in storage capacity. © 2002 Elsevier Science B.V. All rights reserved.
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| 9. |
- Johansson, Pontus, 1974-, et al.
(författare)
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Industrial service profiling : Matching service offerings and processes
- 2004
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Ingår i: International Journal of Production Economics. - 0925-5273 .- 1873-7579. ; 89:3, s. 309-320
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Tidskriftsartikel (refereegranskat)abstract
- Firms using industrial goods as a resource in their own operations need support and services to maintain an efficient use of these resources. Education, spare parts and maintenance are just some examples of services required by many industrial customers. These services make up a large part of many industrial companies purchase budget, but, even more importantly, for the supplier these services often make up a substantial proportion of the company's profit. There is also a trend towards the integration of goods and services. However, there is little help available on strategies for the efficient supply or manufacture of such services. An operations strategy should not be limited to supporting just new sales if the after-sales market of industrial services has a large impact on the company's competitive advantage. A complete operations strategy should therefore be linked not only to the marketing strategy, but also to a service strategy of the company. In this paper we take the supplier's view on the task of providing industrial services, i.e. the supply of after-sales services, including tangibles such as spare parts and consumables, related to the maintenance of industrial goods. We focus on the positioning of industrial services relative manufacturing, aiming at an integrated approach for manufacturing and service operations management. We extend the product-profiling concept of Hill to service operations, developing the concept of industrial service profiling, providing a detailed analysis of market and service offering characteristics relative production characteristics. The resulting profile reveals possible mismatches in the existing operations, and can also be used to identify areas in need of corrective actions.
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| 10. |
- Levén, Erik, et al.
(författare)
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Inventory control with a modified Croston procedure and Erlang distribution
- 2004
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Ingår i: International Journal of Production Economics. - 0925-5273 .- 1873-7579. ; 90:3, s. 361-367
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Tidskriftsartikel (refereegranskat)abstract
- This paper considers an inventory control system, primarily for a finished goods inventory. The purpose is to create a procedure that can handle both fast-moving items with regular demand and slow-moving items. The suggested procedure should be easy to implement in a modern computerized ERP-system. Essentially, the system is a periodic review system built around a Croston forecasting procedure. An Erlang distribution is fitted to the observed data using the mean and variance of the forecasted demand rate. According to probabilities for stock shortages, derived from the probability distribution, the system decides if it is time to place a new order or not. The Croston forecasting method is theoretically more accurate than ordinary exponential smoothing for slow-moving items. However, it is not evident that a Croston forecasting procedure (with assumed Erlang distribution) outperforms ordinary exponential smoothing (with assumed normal distribution) applied in a “practical” inventory control system with varying demand, automatically generated replenishment, etc. Our simulation study shows that the system in focus will present fewer shortages at lower inventory levels than a system based on exponential smoothing and the normal distribution.
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