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  • 1.
    Etembad, Soma
    et al.
    University of Guilan, Sowmeh Sara, Iran.
    Mohammadi Limaei, Soleiman
    University of Guilan, Sowmeh Sara, Iran.
    Olsson, Leif
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    Yousefpour, Rasoul
    University of Freiburg, Freiburg, Germany.
    Decision making on Sustainable Forest Harvest Production Using Goal Programming Approach: Case study: Iranian Hyrcanian Forest2018Conference paper (Refereed)
    Abstract [en]

    This paper aims to determine the optimal stock level in Hyrcanian forest of Iran. In this study, a goal programming techniques used to estimate the optimum stock level of different tree species considering economics, environmental and social issues. We consider multiple objectives in the process of decision making to realize the balance of maximizing annual growth, net present value, carbon sequestration and labor. We use regression analysis to develop a forest growth model using allometric functions for the quantification of carbon budget. The expected mean price was estimated to determine the net present value of forest harvesting. We use Expert knowledge to weight the goals in order to generate the optimal stock level. Results show that the total optimum stock is 0.5% lower than based on questioners. The results indicate that goal programming is a suitable methodology in this case. 

  • 2.
    Gustavsson, Klas
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    L'Ecuyer, Pierre
    Université de Montréal, Canada.
    Olsson, Leif
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    Modeling bursts in the arrival process to an emergency call centerIn: Article in journal (Refereed)
  • 3.
    Gustavsson, Klas
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    Olsson, Leif
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    Gidlund, Mikael
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    Andersson, U
    SOS Alarm Sverige AB, Stockholm, Sweden.
    Simulating traffic management strategies at the Swedish emergency call centerIn: Article in journal (Refereed)
    Abstract [en]

    In telecommunication research, the assessment of strategic and operational performance has gained a lot of interest. So far, the variability within the operational research of telecommunication derives from the stochastic nature of call arrivals, call duration and abandonments. This study extends the stochastic drivers to capacity by incorporating agent behavior. In this study, we model a Discrete-Event-Simulation model of the Swedish emergency call service provider to assist the strategic issue of skills-based routing. Because of the pull system, we designed skills-based routing using an event-dependent overflow setting with a fixed waiting time threshold, where calls become visible to extended agent classes after a threshold value, providing an advantage to primary idle agents to answer before idle secondary agents. Our model mimics the tail of waiting times better than conventional methods. Because of the accompanied calculation opportunities, the model has assisted both strategic and operational issues in the organization. In addition to practical implications, the study proves that the stochastic nature of agent behavior is crucial. From a queueing theory perspective, the study provides interesting routing effects for an event-dependent overflow setting using a fixed waiting time threshold in a combined “X-N-design”, previously unexplored in research.

  • 4.
    Gustavsson, Klas
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    Olsson, Leif
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    Gidlund, Mikael
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    Andersson, Ulf
    SOS Alarm Sverige AB, Stockholm, Sweden.
    Simulating routing strategies of inbound calls at the Swedish emergency call centerIn: European Journal of Industrial Engineering, ISSN 1751-5254, E-ISSN 1751-5262Article in journal (Refereed)
  • 5.
    Hjalmarsson, Victoria
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    Olsson, Leif
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    Quantifying Leanness combining Value Stream Mapping with a Data Envelopment Analysis based method: A case study at a Swedish Logistics Company2017Conference paper (Refereed)
    Abstract [en]

    By describing companies through their processes it is possible to get a well-established overall understanding of the company. This case study is based on the daily operations of a small logistics company specialized in international transportation. We perform Value Stream Mapping in order to propose improvements leading to reduced processing time. Afterwards a Data Envelopment Analysis based method is used to calculate the leanness score of the current system and estimate how much the leanness can increase by the proposed improvements. Results show that waste produced by bad workplace layout and over-processing can be eliminated. A suggested solution is to introduce standardized processes and to invest in technical instruments in order to automate production. According to this study the business is 45 percent lean at present and could with simple improvements soon become 61 percent lean and finally reach an ideal state at 100 percent leanness if production is automated.

  • 6.
    Hultqvist, Daniel
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Physics and Mathematics.
    Olsson, Leif
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Physics and Mathematics.
    A demand-based scenario optimization model for supply of raw material to the forest industry2005In: USDA Forest Service - General Technical Report PNW, ISSN 0887-4840, no 656, p. 331-340Article in journal (Refereed)
    Abstract [en]

    There are usually many sources for the supply of raw material to a pulp or paper mill in Sweden. The decision-maker can procure raw material from the company's own forest(s), buy in from the owners of small forests, swap with other forest operators or purchase on the international market. Wood chips for these mills are brought from sawmills and have their own transportation system, but are included in the model presented here. Optimizing the supply of raw material at a tactical planning level is a challenging task, and can only be managed properly if elements of uncertainty are considered. The solution would otherwise give few options when disturbances occur, for example when weather conditions change. The deterministic equivalent of the scenario model is formulated and solved as a convex mixed integer quadratic model. In this paper, we have focused on model building since this is a challenging task in itself. The model is tested on one small sample problem and one full-scale problem. We show how to simulate and evaluate different strategies in the flow of raw materials, from harvesting operations to delivery at the mills. In our study, the full-scale problem has been solved within reasonable time using commercially available software, and the solution indicates that the hedging effect in the stochastic solution adds flexibility. Future work will involve the development of stochastic programming algorithms to solve large-scale instances of the problem using parallel computing.

  • 7.
    Hultqvist, Daniel
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Physics and Mathematics.
    Olsson, Leif
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Physics and Mathematics.
    Demand based tactical planning of the roundwood supply chain with respect to stochastic disturbances2004Report (Other academic)
  • 8.
    Hultqvist, Daniel
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Physics and Mathematics.
    Olsson, Leif
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Physics and Mathematics.
    Optimization of the raw material procurement at pulp or paper mills: The influence of weather-related risks2006In: International Journal of Systems Science, ISSN 0020-7721, Vol. 37, no 4, p. 253-269Article in journal (Refereed)
    Abstract [en]

    There are usually many sources for the supply of raw material to a pulp or paper mill in Sweden. Optimization of this supply is therefore a challenging task, and can only be managed properly if all aspects of risk are considered. In our study, these risks are related to when the weather reduces the load-bearing capacity of the ground or the roads. A stochastic and a deterministic model have been formulated, and they have been solved with mixed-integer quadratic programming and tested with data from a Swedish forest company. The results of this study show that the option value is greater than zero and that both the optimal policy and the option value change whenever the storage cost is altered. This shows that the optimal planning policy obtained from the stochastic model differs from the solution of the deterministic model.

  • 9.
    Johansson, Jonas
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology. SCA Timber AB.
    Strandberg, Christer
    Mid Sweden University, Faculty of Human Sciences, Department of Business, Economics and Law.
    Olsson, Leif
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    Swedish consumers’ of durable wood materials – value, knowledge and satisfactionArticle in journal (Refereed)
  • 10.
    Kalinina, Maria
    et al.
    Dept. of Computer and Systems Sciences, Stockholm University.
    Larsson, Aron
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information and Communication systems.
    Olsson, Leif
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information and Communication systems.
    Easy-Interactive Ordering of the Pareto Optimal Set with Imprecise Weights2013In: World Academy of Science, Engineering and Technology: An International Journal of Science, Engineering and Technology, ISSN 2010-376X, E-ISSN 2070-3740, no 76, p. 643-648Article in journal (Refereed)
    Abstract [en]

    In the multi objective optimization, in the case when generated set of Pareto optimal solutions is large, occurs the problem to select of the best solution from this set. In this paper, is suggested a method to order of Pareto set. Ordering the Pareto optimal set carried out in conformity with the introduced distance function between each solution and selected reference point, where the reference point may be adjusted to represent the preferences of a decision making agent. Preference information about objective weights from a decision maker may be expressed imprecisely. The developed elicitation procedure provides an opportunity to obtain surrogate numerical weights for the objectives, and thus, to manage impreciseness of preference. The proposed method is a scalable to many objectives and can be used independently or as complementary to the various visualization techniques in the multidimensional case.

  • 11.
    Kalinina, Maria
    et al.
    Inst. för data- och systemvetenskap, Stockholms universitet.
    Larsson, Aron
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Olsson, Leif
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Generating and Ordering of Transport Alternatives in Inter-Modal Logistics in the Presence of Cost, Time, and Emission Conflicts2012In: Proceedings of the 2012 IEEE International Conference on Industrial Engineering and Engineering Management, IEEE conference proceedings, 2012, p. 131-135Conference paper (Refereed)
    Abstract [en]

    Intelligent matching of goods and freight transports is a complex task since different transport modes, such as trains, vessels and trucks have different strengths and weaknesses. Today, however, not only transport cost and time are considered but also the low emission is regarded as an important objective in intermodal freight logistics. The paper describes an approach for generating and ordering transports alternatives in the presence of cost, time, and emission conflicts. In order to obtain a reasonable ordering for generated alternatives we propose the use of the normalized Chebyshev distance between an alternative and a reference point, herein defined as a middle point. By doing so, preference information from a decision maker may be taken into account. The approach is tested on a medium sized problem. The results are promising and indicate the possibility of using the developed method in a decision support system. 

  • 12.
    Kalinina, Maria
    et al.
    Dept. of Computer and Systems Sciences, Stockholm University.
    Olsson, Leif
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information and Communication systems.
    Larsson, Aron
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information and Communication systems.
    A Multi Objective Chance Constrained Programming Model for Intermodal Logistics with Uncertain Time2013In: International Journal of Computer Science Issues, ISSN 1694-0784, E-ISSN 1694-0814, Vol. 10, no 6, p. 35-44Article in journal (Refereed)
    Abstract [en]

    This paper presents a multi objective chance constrained programming model for matching of goods and transports in an intermodal transport chain under uncertain delivery time. The objectives in the proposed model are cost, emission, and transport time, where time is considered as an uncertain parameter. An approach to solve the model is proposed, and this approach has been implemented in a web-based system for transport matching in order to provide clients with alternative transport routes in a large system of possible transport solutions. A case study of a Swedish shipping company is analyzed, and the results are presented through comparisons of results from deterministic and stochastic models. The suggested model can help a decision maker to select transport alternative compromising between time, cost, emission, and with respect to uncertainty in transport time parameters.

  • 13.
    Larsson, Aron
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology. Stockholms Universitet.
    Ibrahim, Osama
    Stockholms Universitet.
    Olsson, Leif
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    van Laere, Joeri
    Högskolan i Skövde.
    Agent Based Simulation of a Payment System for Resilience Assessments2017Conference paper (Refereed)
    Abstract [en]

    We provide an agent based simulation model of the Swedish payment system. The simulation model is to be used to analyze the consequences of loss of functionality, or disruptions of the payment system for the food and fuel supply chains as well as the bank sector. We propose a gaming simulation approach, using a computer based role playing game, to explore the collaborative responses from the key actors, in order to evoke and facilitate collective resilience.

  • 14.
    L'ecuer, Pierre
    et al.
    University of Montreal.
    Gustavsson, Klas
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    Olsson, Leif
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    Modeling Bursts In The Arrival Process To An Emergency Call Center2018In: Proceedings of the 2018 Winter Simulation Conference / [ed] M. Rabe, A. A. Juan, N. Mustafee, A. Skoogh, S. Jain, and B. Johansson, eds, IEEE, 2018, p. 525-- 536Conference paper (Refereed)
    Abstract [en]

    In emergency call centers (for police, firemen, ambulances) a single event can sometimes trigger many incoming calls in a short period of time. Several people may call to report the same fire or the same accident, for example. Such a sudden burst of incoming traffic can have a significant impact on the responsiveness of the call center for other events in the same period of time. We examine data from the SOS Alarm center in Sweden. We also build a stochastic model for the bursts. We show how to estimate the model parameters for each burst by maximum likelihood, how to model the multivariate distribution of those parameters using copulas, and how to simulate the burst process from this model. In our model, certain events trigger an arrival process of calls with a random time-varying rate over a finite period of time of random length.

  • 15.
    Lohmander, Peter
    et al.
    Optimal Solutions.
    Mohammadi, Soleiman
    University opf Guilan, Iran.
    Olsson, Leif
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information and Communication systems.
    Mohammadi, Zohreh
    University of Guilan, Iran.
    Optimal forest management based on growth data from the Iranian Caspian Forest2016Conference paper (Refereed)
    Abstract [en]

    Forest management in the Iranian Caspian Forest is optimized via harvesting decisions based on individual trees. The theory of optimal control in discrete time, stochastic dynamic programming, is applied. The optimization program utilizes new basal area growth and volume functions for beech, estimated via data from the Iranian Caspian forest.

    Recent information about the degree of price variation is used in the optimizations. The optimal control function is defined as a reservation price function, which is determined via backward recursion. The optimal reservation price function and the optimal expected present value function are determined for alternative levels of interest rate and risk. Furthermore, the optimal harvest year and optimal harvest diameter frequency distributions are determined for different degrees of risk and rate of interest. 

  • 16. Lohmander, Peter
    et al.
    Olsson, Leif
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Physics and Mathematics.
    Adaptive optimisation in the roundwood supply chainManuscript (preprint) (Other academic)
  • 17.
    Meng, Xiaozhou
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Thörnberg, Benny
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Olsson, Leif
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Component obsolescence management model for long life cycle embedded system2012In: AUTOTESTCON (Proceedings), Anaheim, California: IEEE conference proceedings, 2012, p. 19-24Conference paper (Refereed)
    Abstract [en]

    This paper discusses the component obsolescence problem and presents a mathematic model for life cycle analysis of long life cycle embedded system maintenance. This model can estimate minimized management costs for different system architecture. Matlab is used to generate a graph and Lingo is used for linear programming. A simple CAN controller system case study is shown to apply this model. A minimized management cost and an optimized management time schedule are given as the result. The responses from the experiments of the model meet our expectation. Although the model has lots of simplifications and limitations, it can give management strategy guidance to the designers who suffer from component obsolescence problems. 

  • 18.
    Meng, Xiaozhou
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Thörnberg, Benny
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Olsson, Leif
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information and Communication systems.
    Strategic Proactive Obsolescence Management Model2014In: IEEE Transactions on Components, Packaging, and Manufacturing Technology, ISSN 2156-3950, E-ISSN 2156-3985, Vol. 4, no 6, p. 1099-1108Article in journal (Refereed)
    Abstract [en]

    When there is a demand larger than the corresponding number of components in stock, obsolescence problems may occur for those systems with a life cycle longer than that of one or more of their components, such as automotive, avionics, military application, etc. This paper discusses the electronic component obsolescence problem and presents a formal mathematical strategic proactive obsolescence management model for long life cycle systems.

    The model presented in this paper utilizes redesign and last-time-buy (LTB) as two management methods. LTB cost is estimated by unit cost, demand quantities, buffer, discount rate and holding cost. Redesign cost is associated with component type and quantities.

    This model can estimate the minimum management costs for a system with different architectures. It consists of two parts. The first is to generate a graph, which is in the form of an obsolescence management diagram. A segments table containing the data of this diagram is calculated and prepared for optimization at a second step. This second part is to find the minimum cost for system obsolescence management. Mixed integer linear programming (MILP) is used to calculate the minimum management cost and schedule. The model is open sourced allowing other research groups to freely download and modify it.

    A display and control system case study is shown to apply this model practically. A reactive manner is presented as a comparison. The result of the strategic proactive management model shows significant cost avoidance as compared to the reactive manner.

  • 19.
    Mohammadi Limaei, Soleiman
    et al.
    University of Guilan, Iran.
    Lohmander, Peter
    Optimal Solutions; Linnéuniversitetet.
    Olsson, Leif
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    Dynamic growth models for continuous cover multi species forestry in Iranian Caspian forests2017In: Journal of Forest Science, ISSN 1212-4834, E-ISSN 1805-935X, Vol. 63, no 11, p. 519-529Article in journal (Refereed)
    Abstract [en]

    This study concerns some of the relevant topics of the Iranian Caspian forestry planning problem, in particular the first central components in this modelling process, such as forest modelling, forest statistics and growth function estimations. The required data such was collected from Iranian Caspian forests.  To do so, 201 sample plots were determined and the parameters such as number of tree, tree diameter at breast height  and trees height were measured at each sample plot. Three sample plots at different 3 elevations were chosen to measure the tree increment. Data has been used to estimate a modified logistic growth model and a model that describes the growth of basal area of individual trees as a function of basal area. General function analysis has been applied in combination with regression analysis. The results are interpreted from ecological perspectives. Furthermore, a dynamic multi species growth model theory is developed and analyzed with respect to dynamic behavior, equilibria, convergence and stability. Logistic growth models have been found useful in continuous cover forest management optimization. Optimization of management decisions in a changing and not perfectly predictable world should always be based on adaptive optimization.

  • 20.
    Mohammadi Limaei, Soleiman
    et al.
    University of Guilan, Iran.
    Lohmander, Peter
    SLU.
    Olsson, Leif
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information and Communication systems.
    SUB MODELS FOR OPTIMAL CONTINUOUS COVER MULTI SPECIES FORESTRY IN IRAN2015In: Proceeeding , 2015Conference paper (Refereed)
    Abstract [en]

    Forestry in Iran is based on continuous cover forestry (CCF) management principles. CCF often leads to higher expected present values than rotation forestry (RF) with clear cuts. Furthermore, CCF has environmental advantages of several kinds. Many different species of trees grow together in large parts of these forests in Iran. Mixed species forests give advantages compared to monocultures, such as options to adapt harvesting of different species to changes in market prices, climate, species specific damages etc. In order to optimize multi species CCF in Iran, it is necessary to develop mathematical models for operations research studies that represent the relevant parts of the Iranian forestry planning problem. This presentation includes central components in this modelling process: Forest statistics, growth function estimations and the links to forest harvesting, logistics and the forest industry mills.  

  • 21.
    Mohammadi, Zohreh
    et al.
    University of Guilan, Iran.
    Mohammadi Limaei, Soleiman
    University of Guilan, Iran.
    Lohmander, Peter
    Optimal Solutions; Linnéuniversitetet.
    Olsson, Leif
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    Estimating the aboveground carbon sequestration and its economic value: case study: Iranian Caspian Forests2017In: Journal of Forest Research, ISSN 1341-6979, E-ISSN 1610-7403, Vol. 63, no 11, p. 511-518Article in journal (Refereed)
    Abstract [en]

    The aim of the study is to estimate the aboveground carbon sequestration and to determine the economicvalue of forests in carbon sequestration as a way of mitigating climate change. This research was conductedat Asalem forests in the north of Iran. In order to estimate the amount of annual carbon sequestration, theannual volume growth of stand was determined using the diameter increment data and tariff. The amount ofcarbon sequestration was estimated based on wood density and using the allometric equation. The carbonmodel was obtained for each species. The value of sequestrated carbon in stumpage and the net present valueof carbon sequestration were determined in order to estimate the economic value of carbon sequestration.Results indicated that the annual volume growth per hectare and the carbon stored are 6.023 m3·yr–1 and2.307 t·ha–1, respectively. Finally, the carbon sequestration value of stumpage and the net present value ofcarbon sequestration are 11,023.753 and 790.361 (10,000 IRR·t–1·ha–1), respectively. Our results are very usefulin estimating the total economic value of Asalem forests and other Iranian Caspian forests in the future.

  • 22.
    Mohammadi, Zohreh
    et al.
    University of Guilan, Iran.
    Mohammadi Limaei, Soleiman
    University of Guilan, Iran.
    Lohmander, Peter
    Optimal Solutions in Cooperation with Linnaeus University, UmeåSweden.
    Olsson, Leif
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    Estimation of a basal area growth model for individual trees in uneven-aged Caspian mixed species forests2018In: Journal of Forestry Research, ISSN 1007-662X, E-ISSN 1993-0607, Vol. 29, no 5, p. 1205-1214Article in journal (Refereed)
    Abstract [en]

    The aim of this study was to estimate a basal area growth model for individual trees in uneven-aged Caspian forests. A survey was conducted in order to find a natural forest without any harvesting activities, a so called ‘untouched forest’ and an area was selected from the Iranian Caspian forest. Three sample plots in the same aspect and of the same forest type were selected. In each plot, total tree height, diameter at breast height, distance of neighbor trees and azimuth were measured. Thirty trees were selected and drilled with increment borer to determine the increment model. Regression analysis was used to estimate the growth model. Results show that, for individual trees, there is a significant nonlinear relationship between the annual basal area increment, as the dependent variable, and the basal area. The results also show that the basal area of competing trees has a positive influence on growth. That the increment is higher with more competing neighboring trees is possibly because plots with higher volume per hectare and more competition, most likely also have higher site index or better soil or better site productivity than the plot with lower volume per hectare.

  • 23.
    Mohammadi, Zohreh
    et al.
    University of Guilan, Iran.
    Mohammadi Limaei, Soleiman
    University of Guilan, Iran.
    Lohmander, Peter
    Optimal Solutions; Linnéuniversitetet.
    Olsson, Leif
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    Estimation of growth model in uneven – aged forests: Case study: Iranian Caspian forests)2017Conference paper (Refereed)
    Abstract [en]

    The aim of this study was to estimate a diameter growth model for individual trees inuneven –aged Caspian forests. Three sample plots in the same aspect and of the same foresttype were selected. In each sample plot, full callipering was conducted and the parameterssuch as total tree height, diameter at breast height, distance of neighbor trees and azimuthwere measured. In each plot, 30 trees were selected and drilled with increment borer, inorder to determine the growth model. Regression analysis was used to estimate the growthmodel. The analysis shows that, for individual trees, there is a strongly significant nonlinearrelation between the annual basal area increment, as the dependent variable, and the basalarea of the individual trees. The results also show, that the basal area of competing trees, inthe sample, has a positive influence on growth. The estimated result that increment is higherwith more competing neighbor trees is probably obtained because of the following reason:The plots with higher volume per hectare, and more “competition”, most likely also havehigher “site index” or “better soil” or “better forest production conditions” than the plotwith lower volume per hectare.

  • 24.
    Olsson, Leif
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Physics and Mathematics.
    Dator beräknar snabbt vilka vägar som bör rustas upp2004Report (Other academic)
  • 25.
    Olsson, Leif
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Physics and Mathematics.
    Hur Meråkersbanan påverkar godstransporterna för Eka Chemicals: Bilaga till NECL slutrapport2006Report (Other scientific)
  • 26.
    Olsson, Leif
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Physics and Mathematics.
    Hur påverkar en ny färjelinje mellan Sundsvall och Kaskö godstransporterna mellan Sverige och Finland?: Del 1: SCA Transforests godsvolymer från Sverige till Finland 20052006Report (Other scientific)
  • 27.
    Olsson, Leif
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Physics and Mathematics.
    Optimal road investments - A forest company case studyManuscript (preprint) (Other academic)
  • 28.
    Olsson, Leif
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Physics and Mathematics.
    Optimal road investments -: A forest company case study2003In: 2nd forest engineering conference, 12-15 may 2003, Växjö Sweden: proceedings : posters : technique and methods, Uppsala Skogforsk: Skogforsk , 2003, p. 138-Conference paper (Refereed)
  • 29.
    Olsson, Leif
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Physics and Mathematics.
    Optimal upgrading of forest road networks: scenario analysis vs stochastic modelling2007In: Forest Policy and Economics, ISSN 1389-9341, E-ISSN 1872-7050, Vol. 9, no 8, p. 1071-1078Article in journal (Refereed)
    Abstract [en]

    A two-stage stochastic model with binary choice in the first stage has been developed to optimise the upgrading of a real-world forest road network, geographically located in the middle of Sweden. We have compared the model with solutions to the same problem from deterministic scenario analysis. Upgrade policies can be achieved swiftly using both approaches, since the road network is of moderate size. However, a deterministic approach is considerably faster when larger problems are involved. The study here, furthermore, indicates that deterministic scenario analysis provides us with quick, near-optimal solutions to the stochastic model, which are of reasonable good quality. We conclude that the model used here is rather insensitive to uncertainty in critical period length, such as the length of spring thaw, at least when applied to the medium-sized problem presented here. Nevertheless, we strongly recommend the use of the stochastic model whenever possible, since the stochastic and deterministic solutions differ, due to the hedging effect in the stochastic solution.

  • 30.
    Olsson, Leif
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Physics and Mathematics.
    Optimisation of Forest Road Investments and the Roundwood Supply Chain2004Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    In a pre-study, concerning roundwood freshness, performed by the Forestry Research Institute of Sweden during the spring of 2000, the quality on the forest road network was identified as a major problem for the Swedish forest sector. These problems mostly occur during spring thaw, but also when rains give muddy gravel roads. The Swedish forest company Holmen Skog decided to support the PhD project presented here with harvest and road data from a forest district, and expert knowledge of road investments.

     

    Upgrading of forest roads has been studied in a major part of this thesis, with two case studies at a forest district of average size located around Sveg in Härjedalen. Deterministic scenario analysis has been used and compared to a two-stage stochastic model. Cost functions, assortment mixtures and scenarios have been analysed, and results have been evaluated together with the staff at Holmen Skog. These case studies indicate that the problem can swiftly be solved, at least at average size forest districts.

     

    In the last paper a model of the roundwood supply chain is developed and tested via a sample problem. The problem is restricted to the supply chain with fixed harvesting and fixed demand at the mills. The considered uncertainty is load-bearing capacity on the road network, which depends on the water content in the road body and the bearing layer quality.

     

    In contrast to the road investment which are long-term decisions, this planning problem is short-term, and in our paper between half a year and one year. One difficult part in this model is the estimation of storage costs. This study, therefore, puts forward the need of measurements of storage costs. Otherwise, it is not possible to optimise the roundwood supply chain in a consistent way. Storage costs should, for that reason, be analysed in the future.

     

     

  • 31.
    Olsson, Leif
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Physics and Mathematics.
    Road investment scenarios in Northern Sweden2005In: Forest Policy and Economics, ISSN 1389-9341, Vol. 7, no 4, p. 615-623Article in journal (Refereed)
  • 32.
    Olsson, Leif
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Larsson, Aron
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Matching of Intermodal Freight Transports Using Optimization in a Decision Support System2012In: Proceedings of the 2012 IEEE International Conference on Industrial Engineering and Engineering Management, IEEE conference proceedings, 2012, p. 313-317Conference paper (Refereed)
    Abstract [en]

    We describe the computational methods to be used in a web based transport matching system in order to providing clients alternative transport routes, and a model for support of combined intermodal transports where time, emissions and costs are jointly handled. We use network optimization and a mixed integer linear model together with subsequent results from a feasibility test carried out within a transport corridor ranging from the west coast of Norway to Finland through Sweden. The test indicates that network optimization is a well suited methodology for this type of problem, providing swift solutions for the selected problem which is of a medium size with respect to the network size. Future development will be focused on the extension and implementation of this model in a web-based multi-criteria decision support system, able to handle conflicts between cost, time, and emissions in the recommendation of admissible transport solutions.

  • 33.
    Olsson, Leif
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Physics and Mathematics.
    Lohmander, P.
    Optimal forest transportation with respect to road investments2005In: Forest Policy and Economics, ISSN 1389-9341, Vol. 7, no 3, p. 369-379Article in journal (Refereed)
  • 34.
    Olsson, Leif
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Physics and Mathematics.
    Ohmander, P
    Adaptive optimisation in the roundwood supply chain2002In: Bornholm '02 / Nordic summer course on applied optimization and modeling, May 5 - 11, 2002: Nordic summer course on applied optimization and modeling (2002 : Bornholm), Linköping: Univ., Dept. of mathematics , 2002, p. 193-Conference paper (Refereed)
  • 35.
    Olsson, Leif
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information and Communication systems.
    Zadmirzaei, Majid
    University of Guilan, Iran.
    Mohammadi, Soleiman
    University of Gulan, Iran.
    Amirteimoori, Alireza
    University of Guilan, Iran.
    Measuring the performance and returns to scale of forest management units in the north of Iran based on the non-parametric approach (DEA)2015Conference paper (Refereed)
    Abstract [en]

    The aim of this study is to assess the relative efficiency of Iranian forest management units using the non-parametric method Data envelopment analyses (DEA). To this end, DEA as a well-known and robust technique for measuring the relative efficiency of organizations is used. The relative efficiency of comparable forest plans was calculated with the most frequently used DEA models – CCR, BCC and SE[LO1] . According to the results of global technical efficiency (CCR) and local pure technical efficiency (BCC), the efficiency averages were 0.83 and 0.93, respectively. The results of scale efficiency (SE) discussed a worrying aspect of these units’ efficiency; namely, there were only 3 efficient forestry plans (Shafaroud, Nav and Fiyab). However, using the Scale Efficiency Index (SEI) or FGL-DEA model brings out some interesting points; there were approximately 58% (7 units out of 12) under Increasing Returns to Scale (IRS). Thus, the managers of forest plans should more focus on forest plans under IRS so that they have the opportunity to become more efficient through growth, otherwise managers will not be able to promote their overall productivity.   

  • 36.
    Thörnberg, Benny
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Physics and Mathematics.
    Olsson, Leif
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Physics and Mathematics.
    O'Nils, Mattias
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Optimization of memory allocation for real-time video processing on FPGA2005In: 16th International Workshop on Rapid System Prototyping, Proceedings - SHORTENING THE PATH FROM SPECIFICATION TO PROTOTYPE, IEEE conference proceedings, 2005, Vol. 2005, p. 141-147Conference paper (Refereed)
    Abstract [en]

    We present an optimization model for the allocation of shift registers to dual ported FPGA memory blocks. Shift registers are used in real-time video processing for the storage of data flow dependencies. The model is formalized into a mixed integer linear program that can be executed using a general solver. Allocation results from realistic video systems verify the correctness of the model. This model serves as a formal specification and setup for the development of an efficient allocation heuristic.

  • 37.
    Thörnberg, Benny
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Palkovic, Martin
    Hu, Qubo
    Olsson, Leif
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Physics and Mathematics.
    Kjeldsberg, Per Gunnar
    O'Nils, Mattias
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Catthor, Francky
    Bit-Width Constrained Memory Hierarchy Optimization for Real-Time Video Systems2007In: IEEE Transactions on Computer-Aided Design of Integrated Circuits and Systems, ISSN 0278-0070, E-ISSN 1937-4151, Vol. 26, no 4, p. 781-800Article in journal (Refereed)
    Abstract [en]

    The great variety of pixel dynamics of real-time video processing systems, ranging from color, grayscale or binary pixels, means that a careful design and specification of bit-widths is required. It is obvious that the bit-width specification will affect the total memory storage requirement. However, what is not so obvious is that the bit-width specification will also affect the design of the memory hierarchy, an impact similar for both hardware and software implementations. We have developed an Integer Non Linear Program (INLP) formulation for the optimization of the memory hierarchy of real-time video processing systems. An active surveillance video camera is introduced as a test case. We demonstrate how the optimization model can reduce the on-chip memory storage by 61 percent compared to a non optimal memory hierarchy.

  • 38. Timpe, Daniel
    et al.
    Olsson, Leif
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Sidén, Johan
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Cost analysis of introducing a log identification system using RFID in the wood supply chain: A case study at a Swedish forest company2012In: American Journal of Industrial and Business Management, ISSN 2164-5167, Vol. 2, no 4, p. 128-135Article in journal (Refereed)
    Abstract [en]

    A cost analysis for the possibility of a log identification system using Radio Frequency Identification (RFID) is presented in this paper. The introduction provides a brief description of the RFID technology and its usefulness within the area of forest logistics. Information network mapping is used to facilitate an understanding of the current information flow and identification requirements along the supply chain. The cost analysis is performed using the method of break-even analysis using nine different scenarios by means of a case study at the Ortviken paper mill, which is located in central Sweden. The analyses of the processes in the supply chain revealed that the potential exists to streamline operations and to make more efficient use of the available resources by implementing an open loop RFID-based log tracking system in the supply chain using read only tags. Furthermore, this study indicates that even in those cases in which RFID does not provide any major improvements to the firm’s inventory management; it is still possible to achieve economic benefits. However, implementation of such a system will require further development of, in particular, the RFID tags to satisfy the feasibility requirements in the wood supply chain.

  • 39.
    Truex, Duane
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Olssson, Leif
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Lindblad-Gidlund, Katarina
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Sefyrin, Johanna
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Larsson, Aron
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Nilsson, Olof
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Anderson, Karen
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Borglund, Erik
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Asproth, Viveca
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Position Statement: Sustainable Information and Information Systems (SIIS)2011In: Governance and Sustainability in Information Systems: Managing the Transfer and Diffusion of ITManaging the Transfer and Diffusion of IT, IFIP / [ed] Karlheinz Kautz, Markus Nüttgens, & Andreas Gadatsch, Hamburg Germany: Springer, 2011, p. 306-309Conference paper (Refereed)
    Abstract [en]

    In this position statement we provide our understanding of the relation between the IS field and the notion of sustainability, and present our focus through a characterization of the “sustainability research” construct. By doing so, we hope to contribute to the discourse on a clarification of the construct itself in our research community.

  • 40.
    van Laere, Joeri
    et al.
    University of Skövde.
    Berggren, Peter
    Linköping University.
    Gustavsson, Per
    Combitech.
    Ibrahim, Osama
    Stockholm University.
    Johansson, Björn
    Linköping University.
    Larsson, Aron
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    Lindqwister, Towe
    Combitech.
    Olsson, Leif
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    Wiberg, Christer
    Combitech.
    Challenges for critical infrastructure resilience: cascading effects of payment system disruptions2017In: Proceedings of the International ISCRAM Conference, ISCRAM, 2017, Vol. 2017-May, p. 281-292Conference paper (Refereed)
    Abstract [en]

    Critical infrastructures become more and more entangled and rely extensively on information technology. A deeper insight into the relationships between critical infrastructures enables the actors involved to more quickly understand the severity of information technology disruptions and to identify robust cross-functional mitigating actions. This study illustrates how and why disruptions in the payment system in Sweden could create cascading effects in other critical infrastructures with potentially severe consequences for many citizens, government institutions and companies. Data from document studies, interviews and workshops with field experts reveal seven challenges for collective cross-functional critical infrastructure resilience that need to be dealt with: 1)Shortage of food, fuel, cash, medicine; 2) Limited capacity of alternative payment solutions; 3) Cities are more vulnerable than the countryside; 4) Economically vulnerable groups in society are more severely affected; 5)Trust maintenance needs; 6) Crisis communication needs; 7) Fragmentation of responsibility for critical infrastructures across many actors.

  • 41.
    van Laere, Joeri
    et al.
    Högskolan i Skövde.
    Ibrahim, Osama
    Stockholms Universitet.
    Larsson, Aron
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    Olsson, Leif
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    Johansson, Björn
    Linköpings Universitet.
    Gustavsson, Per
    Combitech AB, Skövde.
    Analyzing the implications of design choices in existing simulation-games for critical infrastructure resilience2018In: Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics), Springer, 2018, Vol. 10825, p. 15-23Conference paper (Refereed)
  • 42.
    Vickman, Sara
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Larsson, Aron
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Olsson, Leif
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Prerequisites for decision aid in socially responsible investment appraisals2012In: International Journal of Engineering Management and Economics (IJEME), ISSN 1756-5154, E-ISSN 1756-5162, ISSN 1756-5154, Vol. 3, no 4, p. 359-377Article in journal (Refereed)
    Abstract [en]

    This paper explores investment appraisals restrained by various sources of uncertainty and influenced by socially responsible investment (SRI) thinking. Of particular interest in this paper is to assess the additional aspects of investment appraisals that derive from SRI thinking together with the multiple sources of uncertainty arising in such decision problems. We assess characteristics of how managers' try to account for corporate social responsibility, how they cope with evaluating upon objectives beyond monetary return on investment and how they manage uncertainty and the source of the uncertainties they emphasise. We conclude that organisations are generally exposed to and also consider both aleatory and epistemic uncertainty. There is a mix of macro and micro variables creating a diversified environment where valuation methods such as real options in combination with decision analysis modelling could help in structuring the problem and provide informed decision making.

  • 43.
    Zadmirazaei, Majid
    et al.
    University of Guilan, Iran.
    Mohmmadi Limaei, Soleiman
    University of Guilan, Iran.
    Olsson, Leif
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    Amirteimoori, Alireza
    Islamic Azad University, Iran.
    Assessing the impact of the external non-discretionary factor on the performance of forest management units using DEA approach2017In: Journal of Forest Research, ISSN 1341-6979, E-ISSN 1610-7403, Vol. 22, no 3, p. 144-152Article in journal (Refereed)
    Abstract [en]

    The purpose of this paper is to measure the relative performance of forest management units, and to analyze the impact of the external non-discretionary (ND) factors on these units' technical efficiency. Toward this end, data envelopment analysis (DEA) technique in variable returns to scale environment with both discretionary and ND factors has been used. The required data are collected from 24 Iranian forest management units (as decision-making units (DMUs)) and included four inputs and two outputs. The ND factors are first ignored and it is shown that most of the forest management units are operating at high efficiency levels. Then the variable area is considered as the exogenously fixed (or the external ND) input in a modified ND model because it is outside of the forest manager's control. The results indicate that the number of efficient units and the average technical efficiency score are reduced to 12 (approximately 50%) and 0.85, respectively. The forest management units should therefore increase their average efficiency score by 0.15 to move onto the new efficient frontier which is made by applying this strict criterion. As a consequence, it is recommended to apply the ND models for controlling the exogenously fixed factors and carrying out a correct and accurate evaluation, because the traditional DEA approaches may overestimate the efficiency of DMUs.

  • 44.
    Zadmirazei, Majid
    University of Guilan, Iran.
    Olssson, Leif (Contributor)
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information and Communication systems.
    Amitermoori, Alireza (Contributor)
    Islamic Azad Universityof Rasht, Iran.
    Measuring the performance and returns to scale of forest management plans using data envelopment analysis approach: Case study; Iranian Caspian forests2016In: Caspian Journal of Environmental Sciences, ISSN 1735-3033, Vol. 14, no 2, p. 155-164Article in journal (Refereed)
    Abstract [en]

    The aim of this study was to assess the relative efficiency of the Iranian forest management plans using the non-parametric method – Data Envelopment Analysis (DEA) as a well-known and robust technique for measuring the relative efficiency of organizations. The relative efficiency of forest management plans was calculated using the most frequency DEA models such as global technical efficiency (CCR), local pure technical efficiency (BCC) and Scale Efficiency (SE) on 12 units in Guilan Province, Iran. According to the results of CCR and BCC models, the efficiency averaged 0.83 and 0.93, respectively. The results of SE discussed a worrying aspect of these units efficiency; namely, there were only 3 efficient forest management plans (Shafaroud, Nav and Fiyab). However, the Scale Efficiency Index (SEI) brings out some interesting points; there were approximately 58% (7 units out of 12) under Increasing Returns to Scale (IRS). Therefore, the managers of forest management plans should  focus more on the plans under IRS, so that they will have the opportunity to become more efficient through growth, otherwise managers will not be able to promote their overall productivity.

  • 45.
    zadmirzaei, Majid
    et al.
    University of Guilan.
    Mohammadi Limaei, Solieman
    University of Guilan.
    Amirteimoori, Alireza
    Olsson, Leif
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    Measuring the relative performance of forest management units: A chance-constrained DEA model in the presence of the non-discretionary factor2019In: Canadian Journal of Forest Research, ISSN 0045-5067, E-ISSN 1208-6037Article in journal (Refereed)
    Abstract [en]

    In this study, we develop a marginal chance-constrained data envelopment analysis model in the presence of non-discretionary inputs and hybrid outputs for the first time. We call it a stochastic non-discretionary DEA model (SND-DEA), and it is developed to measure and compare the relative efficiency of forest management units under different environmental management systems. Furthermore, we apply an output-oriented DEA technology to both deterministic and stochastic scenarios. The required data are collected from 24 forest management plans (as decision-making units and included four inputs and equal amount of outputs. The findings of this practical research show that the modified SND-DEA model in different probability levels give us apparently different results compared to the output from pure deterministic models. However, when we calculate the correlation measure, the probability levels give us a strong positive correlation between stochastic and deterministic models. Therefore, approximately 40% of the forest management plans based on the applied SND-DEA model should substantially increase their average efficiency score. As the major conclusion, our developed SND-DEA model is a suitable improvement over previous developed models to discriminate the efficiency and/or the inefficiency of decision-making units to hedge against risk and uncertainty in this type of forest management problems.

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