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Rönnqvist, Mikael
Publications (10 of 65) Show all publications
Gunnarsson, H. & Rönnqvist, M. (2008). Solving a multi-period supply chain problem for a pulp company using heuristics—An application to Södra Cell AB. International Journal of Production Economics, 116(1), 75-94
Open this publication in new window or tab >>Solving a multi-period supply chain problem for a pulp company using heuristics—An application to Södra Cell AB
2008 (English)In: International Journal of Production Economics, ISSN 0925-5273, E-ISSN 1873-7579, Vol. 116, no 1, p. 75-94Article in journal (Refereed) Published
Abstract [en]

In this paper, the integrated planning of production and distribution for a pulp company is considered. The tactical decisions included regard transportation of raw materials from harvest areas to pulp mills; production mix and contents at pulp mills; inventory; distribution of pulp products from mills to customers and the selection of potential orders and their levels at customers. The planning period is one year and several time periods are included. As a solution approach we make use of two different heuristic approaches. The main reason to use heuristics is the need for quick solution times. The first heuristic is based on a rolling planning horizon where iteratively a fixed number of time periods is taken into consideration. The second heuristic is based on Lagrangian decomposition and subgradient optimization. This provides optimistic bounds of the optimal objective function value that are better than the LP relaxation value, which can be used as a measure of the heuristic (pessimistic) solution quality. In addition, we apply the proposed rolling horizon heuristic in each iteration of the subgradient optimization. A number of cases based on real data is analysed which shows that the proposed solution approach is simple and provides high quality solutions.

Place, publisher, year, edition, pages
Elsevier, 2008
Keywords
Supply chain modelling, Production planning, Heuristics, Lagrangian decomposition
National Category
Social Sciences
Identifiers
urn:nbn:se:liu:diva-14850 (URN)10.1016/j.ijpe.2008.07.010 (DOI)000261007900006 ()
Note

Original publication: Helene Gunnarsson and Mikael Rönnqvist, Solving a multi-period supply chain problem for a pulp company using heuristics—An application to Södra Cell AB, 2008, International Journal of Production Economics. http://dx.doi.org/10.1016/j.ijpe.2008.07.010. Copyright: Elsevier B.V., http://www.elsevier.com/

Available from: 2008-09-26 Created: 2008-09-26 Last updated: 2017-12-13Bibliographically approved
Lidestam, H. & Rönnqvist, M. (2008). Solving a multi-period supply chain problem for a pulp company using Lagrangian heuristics based on physical stages. In: Beyond Business Logistics (pp. 233-248). Helsinki, Finland: Anniversary NOFOMA
Open this publication in new window or tab >>Solving a multi-period supply chain problem for a pulp company using Lagrangian heuristics based on physical stages
2008 (English)In: Beyond Business Logistics, Helsinki, Finland: Anniversary NOFOMA , 2008, p. 233-248Conference paper, Published paper (Other academic)
Abstract [en]

  

Place, publisher, year, edition, pages
Helsinki, Finland: Anniversary NOFOMA, 2008
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-43592 (URN)74347 (Local ID)74347 (Archive number)74347 (OAI)
Available from: 2009-10-10 Created: 2009-10-10 Last updated: 2011-05-11
Bredström, D. & Rönnqvist, M. (2007). A branch and price algorithm for the combined vehicle routing and scheduling problem with synchronization constraints. Social Science Research Network, 7
Open this publication in new window or tab >>A branch and price algorithm for the combined vehicle routing and scheduling problem with synchronization constraints
2007 (English)In: Social Science Research Network, Vol. 7Article in journal (Refereed) Published
Abstract [en]

In this paper we present a branch and price algorithm for the combined vehicle routing and scheduling problem with synchronization constraints. The synchronization constraints are used to model situations when two or more customers need simultaneous service. The synchronization constraints impose a temporal dependency between vehicles, and it follows that a classical decomposition of the vehicle routing and scheduling problem is not directly applicable. With our algorithm, we have solved 44 problems to optimality from the 60 problems used for numerical experiments. The algorithm performs time window branching, and the number of subproblem calls is kept low by adjustment of the columns service times.

Keywords
Routing, Scheduling, Synchronization, Branch and Price
National Category
Mathematics
Identifiers
urn:nbn:se:liu:diva-13129 (URN)
Available from: 2008-04-02 Created: 2008-04-02 Last updated: 2009-04-15
Gunnarsson Lidestam, H., Rönnqvist, M. & Carlsson, D. (2007). Integrated production and distribution planning for S¨odra Cell AB. Journal of Mathematical Modelling and Algorithms, 6(1), 25-45
Open this publication in new window or tab >>Integrated production and distribution planning for S¨odra Cell AB
2007 (English)In: Journal of Mathematical Modelling and Algorithms, ISSN 1570-1166, Vol. 6, no 1, p. 25-45Article in journal (Refereed) Published
Abstract [en]

In this paper we consider integrated planning of transportation of raw material, production and distribution of products of the supply chain at Södra Cell AB, a major European pulp mill company. The strategic planning period is one year. Decisions included in the planning are transportation of raw materials from harvest areas to pulp mills, production mix and contents at pulp mills, distribution of pulp products from mills to customer via terminals or directly and selection of potential orders and their levels at customers. Distribution is carried out by three different transportation modes; vessels, trains and trucks. We propose a mathematical model for the entire supply chain which includes a large number of continuous variables and a set of binary variables to reflect decisions about product mix and order selection at customers. Five different alternatives regarding production mix in a case study carried out at Södra Cell are analyzed and evaluated. Each alternative describes which products will be produced at which pulp mills.

Keywords
supply chain management; production planning; modelling; transportation; distribution, integer programming
National Category
Mathematics
Identifiers
urn:nbn:se:liu:diva-14463 (URN)10.1007/s10852-006-9048-z (DOI)
Available from: 2007-05-14 Created: 2007-05-14
Gunnarsson, H. & Rönnqvist, M. (2007). Solving a multi-period supply chain problem for a pulp industry using Lagrangian heuristics based on time periods. Linköping: Linköpings universitet
Open this publication in new window or tab >>Solving a multi-period supply chain problem for a pulp industry using Lagrangian heuristics based on time periods
2007 (English)Report (Other academic)
Place, publisher, year, edition, pages
Linköping: Linköpings universitet, 2007
Series
LiTH-MAT-R ; 5
National Category
Mathematics
Identifiers
urn:nbn:se:liu:diva-38248 (URN)LiTH-MAT-R-2007-08 (ISRN)43185 (Local ID)43185 (Archive number)43185 (OAI)
Available from: 2009-10-10 Created: 2009-10-10
Gunnarsson (Lidestam), H., Rönnqvist, M. & Carlsson, D. (2006). A combined terminal location and ship routing problem. Journal of the Operational Research Society, 57(8), 928-938
Open this publication in new window or tab >>A combined terminal location and ship routing problem
2006 (English)In: Journal of the Operational Research Society, ISSN 0160-5682, Vol. 57, no 8, p. 928-938Article in journal (Refereed) Published
Abstract [en]

In this paper, we consider a combined terminal location and ship routing problem at Södra Cell AB. The purpose is to supply the customers' annual demand for pulp products while minimizing the distribution costs. Customers are supplied with various pulp products from pulp mills in Scandinavia by ships, trains, or lorries. The ship routes go from the pulp mills to terminals in Europe. From each terminal, the products are transported to customers by lorry, train, or barge. Some customers can be supplied directly from the pulp mills by trains or lorries. We have developed a mathematical model to select which terminals to use and, at the same time, determine the shipping routes. The mixed integer programming model was solved directly using a commercial solver. When the number of routes generated is large, the time required to obtain an optimal solution is too long. Hence, we have developed heuristics in order to obtain an acceptable solution in reasonable time. In addition to the basic case, five different scenarios were tested. Our heuristics provide solutions that are within 0.12% of the optimal ones.

Keywords
mixed integer programming, facility location, transportation, ship routing
National Category
Mathematics
Identifiers
urn:nbn:se:liu:diva-14462 (URN)10.1057/palgrave.jors.2602057 (DOI)
Available from: 2007-05-14 Created: 2007-05-14 Last updated: 2013-11-07
Bredström, D. & Rönnqvist, M. (2006). Combined vehicle routing and scheduling with temporal precedence and synchronization constraints. EconPapers, 18
Open this publication in new window or tab >>Combined vehicle routing and scheduling with temporal precedence and synchronization constraints
2006 (English)In: EconPapers, Vol. 18Article in journal (Other academic) Published
Abstract [en]

We present a mathematical programming model for the combined vehicle routing and scheduling problem with time windows and additional temporal constraints. The temporal constraints allow for imposing pairwise synchronization and pairwise temporal precedence between customer visits, independently of the vehicles. We describe some real world problems where the temporal constraints, in the literature, usually are remarkably simplified in the solution process, even though these constraints may significantly improve the solution quality and/or usability. We also propose an optimization based heuristic to solve real size instances. The results of numerical experiments substantiate the importance of the temporal constraints in the solution approach. We also make a computational study by comparing a direct usage of a commercial solver against the proposed heuristic where the latter approach can find high quality solutions within distinct time limits.

Keywords
Routing; Scheduling; Temporal Constraints; Synchronization; Branch and Bound
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-13128 (URN)
Available from: 2008-04-02 Created: 2008-04-02 Last updated: 2009-02-17
Eveborn, P., Flisberg, P. & Rönnqvist, M. (2006). Laps Care: an operational system for staff planning of home care. European Journal of Operational Research, 171(3), 962-976
Open this publication in new window or tab >>Laps Care: an operational system for staff planning of home care
2006 (English)In: European Journal of Operational Research, ISSN 0377-2217, E-ISSN 1872-6860, Vol. 171, no 3, p. 962-976Article in journal (Refereed) Published
Abstract [en]

The health care system in Sweden and many other countries is facing increasing costs. The major reason is the changing age distribution of the population with more elderly people in need of support. At the same time, health care systems are often very labor and staff intensive. In this paper, we focus on a staff planning problem arising in Sweden where people receive home care from the local authorities. The objective is to develop visiting schedules for care providers that incorporate some restrictions and soft objectives. Each visit has a particular task to be performed, for example: cleaning, washing, personal hygiene and/or nursing activities. Each staff member has skills and each client should, if possible, be visited by the same contact person. The operational situation is continuously changing and planning is done each day. We describe the development of a decision support system Laps Care to aid the planners. The system consists of a number of components including information data bases, maps, optimization routines, and report possibilities. We formulate the problem using a set partitioning model and, for a solution method, we make use of a repeated matching algorithm. The system is currently in operation at a number of home care organizations. We report on the practical impact of the system in the health care organization which was involved in the development. The savings are considerably in terms of saved planning time and in the quality of the routes, as well as the measured quality for the clients. Numerical experiments of the system are presented.

Keywords
health care; home care; staff planning; modelling; heuristics; optimization; practice of OR
National Category
Social Sciences
Identifiers
urn:nbn:se:liu:diva-53494 (URN)10.1016/j.ejor.2005.01.011 (DOI)
Available from: 2010-01-25 Created: 2010-01-25 Last updated: 2017-12-12
Bredström, D. & Rönnqvist, M. (2006). Supply chain optimization in pulp distribution using a rolling horizon solution approach. , 17
Open this publication in new window or tab >>Supply chain optimization in pulp distribution using a rolling horizon solution approach
2006 (English)Report (Other academic)
Abstract [en]

In this paper we consider a combined supply chain and ship routing problem for a large pulp producer in Scandinavia. The problem concerns the distribution of pulp to customers, with route scheduling of ships as a central part of modeling. It is an operative planning problem with daily ship routing decisions over a 40 days period. The pulp supply is determined by fixed production plans, and the transport flows and storages are modeled with the requirement to satisfy the demand in a cost-optimal way. We develop a mixed integer programming model with binary variables for route usage of a vessel.

The problem is solved with a heuristic solution method, based on a rolling time horizon and a standard branch and bound algorithm. We apply the heuristic on problem instances with real world data, and compare results from reduced problem instances with the results from an exact branch and bound search. The computational experiments indicate that real world problems are solvable with the solution method and that it in many cases can be very effcient.

 

Series
LiTH-MAT-R ; 2003-25
Keywords
Supply chain, Ships, Scheduling, Mixed integer programming
National Category
Mathematics
Identifiers
urn:nbn:se:liu:diva-13131 (URN)
Available from: 2008-04-02 Created: 2008-04-02 Last updated: 2013-11-05
Bredström, D., Rönnqvist, M. & Carlsson, D. (2005). A hybrid algorithm for a pulp distribution problem. IEEE Intelligent Systems, 20(4), 19-25
Open this publication in new window or tab >>A hybrid algorithm for a pulp distribution problem
2005 (English)In: IEEE Intelligent Systems, ISSN 1541-1672, Vol. 20, no 4, p. 19-25Article in journal (Refereed) Published
Abstract [en]

Distribution is a major factor in the supply chain for Sodra Cell, a leading manufacturer of pulp intended for paper production. Each year, the company transports large quantities of pulp using ships, trains, and trucks; here we focus on scheduling the ships and optimizing deliveries to minimize distribution costs.

National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-13132 (URN)10.1109/MIS.2005.59 (DOI)
Available from: 2008-04-02 Created: 2008-04-02 Last updated: 2015-12-29
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