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Articles containing the keyword 'optimisation'

Category : Research article

article id 23032, category Research article

Maria Anna Gartner, Matthias Kaltenbrunner, Manfred Gronalt. (2024). Dynamic box assignment planning in log yards. Silva Fennica vol. 58 no. 1 article id 23032. https://doi.org/10.14214/sf.23032

Keywords: storage assignment; seasonality; binary integer program; optimisation model; sawmill storage

Highlights: Seasonal change of assortments calls for dynamic box assignment planning in log yards; Multi-period planning better suited for dynamic problem, however period per period planning improves with decreasing capacity on the log yard; Rearrangement of assortment amounts to 8–11% of total transportation distance (loaded travelled distances of transportation vehicle); Considering separate box allocation (storage and ejection), which results in double stage planning of box allocation, benefits most if 10% additional volume may be cut in to clear the box.

Abstract | Full text in HTML | Full text in PDF | Author Info

The situation on the log yard changes seasonally and also over the years. The quantities of assortments to be stored, their number and also the type of wood can change. To respond to this, we have developed a dynamic log yard planning model for assigning roundwood to specific ejection boxes and storage areas in order to minimise the overall transport distances of the loaded transportation vehicles on the log yard, including any possible re-allocation of assortments. The study centres on the log yard of a medium-sized hardwood sawmill in Europe, with actual cutting data from a six-month period. We are comparing a multi-period binary integer program with a model that operates on a period per period basis and a solution approach that splits the problem into two subproblems and solves them sequentially. The models undergo testing with decreasing space capacities at the storage boxes on the log yard and are compared. If capacity is continuously decreasing from 100% to 80%, then period per period planning is on average 13% worse than multi-period planning. We also investigate how the solutions change when twice as many or half as many assortments are stored at the log yard. In addition, we study how much the solutions improve when logs can be removed from the storage boxes to clear them and release them for other material in the following period.

Gartner, University of Natural Resources and Life Sciences, Department of Economics and Social Sciences, Institute of Production and Logistics, Feistmantelstrasse 4, 1180 Vienna, Austria https://orcid.org/0000-0001-8547-718X E-mail: maria.gartner@boku.ac.at
Kaltenbrunner, improvem GmbH, Holzinnovationszentrum 1a, 8740 Zeltweg, Austria https://orcid.org/0000-0002-1178-0087 E-mail: matthias.kaltenbrunner@improvem.at
Gronalt, University of Natural Resources and Life Sciences, Department of Economics and Social Sciences, Institute of Production and Logistics, Feistmantelstrasse 4, 1180 Vienna, Austria https://orcid.org/0000-0003-0944-4911 E-mail: manfred.gronalt@boku.ac.at

article id 928, category Research article

Rune Simonsen. (2013). Optimal regeneration method – Planting vs. natural regeneration of Scots pine in northern Sweden. Silva Fennica vol. 47 no. 2 article id 928. https://doi.org/10.14214/sf.928

Keywords: optimisation; silviculture; genetically improved planting material

Highlights: Two regeneration methods were modelled on stand level and optimised numerically to maximise present value for a range of site indexes and locations; Natural regeneration was optimal in most cases; Planting was optimal for high site indexes, low rate of seedling mortality and for low discount rates; Using genetically improved plant material greatly shifts the preference towards planting

Abstract | Full text in HTML | Full text in PDF | Author Info

In this study the profitability of regenerating Scots pine (Pinus sylvestris L.) was examined for two methods; planting and natural regeneration with seed trees. The methods were modelled on stand level and optimised numerically using nonlinear optimisation. The analysis includes 7 site indexes, 16 to 28 expressed as dominant height in meters at an age of 100 years; and 8 localities in northern Sweden distributed on two latitudes, 60°N and 64°N and four altitudes, 100 to 400 m.a.s.l. Furthermore, two scenarios of genetically improved planting material were examined. The results show that the optimal choice of regeneration method depends on the location, site index and discount rate. Considering the same genetic regeneration material, natural regeneration was the optimal method for most of the evaluated sites. Planting was optimal only for stands of high site index and low rate of seedling mortality, which is associated with localities on low altitudes. The break even site index, where the two methods yielded the same net present value, was 27 on average (25 to 28). The choice between the two regeneration methods was found to be more economically important when the discount rate was low and for low site indexes. The option of using genetically improved plant material shift the preference towards planting. Thus, the two levels of genetic gain of +4% and +10% to maximum mean annual increment resulted in an average break even site index of 25 and 21 respectively.

Simonsen, Department of Forest Economics, SLU, SE-901 83 Umeå, Sweden E-mail: rune.simonsen@slu.se

article id 109, category Research article

Ann Kristin Raymer, Terje Gobakken, Birger Solberg. (2011). Optimal forest management with carbon benefits included. Silva Fennica vol. 45 no. 3 article id 109. https://doi.org/10.14214/sf.109

Keywords: forest management; Norway spruce; substitution; CO2; greenhouse gas mitigation; optimisation; wood products

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In this paper, we analyse how optimal forest management of even aged Norway spruce changes when economic values are placed on carbon fixation, release, and saved greenhouse gas emissions from using wood instead of more energy intensive materials or fossil fuels. The analyses are done for three different site qualities in Norway, assuming present climate and with a range of CO₂ prices and real rates of return. Compared to current recommended management, the optimal number of plants per ha and harvest age are considerably higher when carbon benefits are included, and increase with increasing price on CO₂. Furthermore, planting becomes more favourable compared to natural regeneration. At the medium site quality, assuming 2% p.a. real rate of return and 20 euros per ton CO₂, optimal planting density increases from 1500 per ha to 3000 per ha. Optimal harvest age increases from 90 to 140 years. Including saved greenhouse gas emissions when wood is used instead of more energy intensive materials or fossil fuels, i.e. substitution effects, does not affect optimal planting density much, but implies harvesting up to 20 years earlier. The value of the forest area increases with increasing price on CO₂, and most of the income is from carbon. By using the current recommended management in calculations of carbon benefit, our results indicate that the forest’s potential to provide this environmental good is underestimated. The study includes many uncertain factors. Highest uncertainty is related to the accuracy of the forest growth and mortality functions at high stand ages and densities, and that albedo effects and future climate changes are not considered. As such, the results should be viewed as exploratory and not normative.

Raymer, Norwegian University of Life Sciences, Department of Ecology and Natural Resource Management, P.O. Box 5003, N-1432 Ås, Norway E-mail: akr@nn.no
Gobakken, Norwegian University of Life Sciences, Department of Ecology and Natural Resource Management, P.O. Box 5003, N-1432 Ås, Norway E-mail: terje.gobakken@umb.no
Solberg, Norwegian University of Life Sciences, Department of Ecology and Natural Resource Management, P.O. Box 5003, N-1432 Ås, Norway E-mail: bs@nn.no

article id 474, category Research article

Tero Heinonen, Mikko Kurttila, Timo Pukkala. (2007). Possibilities to aggregate raster cells through spatial optimization in forest planning. Silva Fennica vol. 41 no. 1 article id 474. https://doi.org/10.14214/sf.474

Keywords: threshold accepting; spatial optimisation; landscape metrics; old forest

Abstract | View details | Full text in PDF | Author Info

Heinonen, University of Joensuu, Faculty of Forestry, P.O. Box 111, FI-80101 Joensuu, Finland E-mail: tero.heinonen@joensuu.fi
Kurttila, Finnish Forest Research Institute, Joensuu Research Unit, P.O. Box 68, FI-80101 Joensuu, Finland E-mail: mk@nn.fi
Pukkala, University of Joensuu, Faculty of Forestry, P.O. Box 111, FI-80101 Joensuu, Finland E-mail: tp@nn.fi

article id 419, category Research article

Tero Heinonen, Timo Pukkala. (2004). A comparison of one- and two-compartment neighbourhoods in heuristic search with spatial forest management goals. Silva Fennica vol. 38 no. 3 article id 419. https://doi.org/10.14214/sf.419

Keywords: simulated annealing; Hero; tabu search; 2-optimal heuristic; spatial optimisation; random ascent

Abstract | View details | Full text in PDF | Author Info

This study presents a comparison of the performance of four heuristic techniques with one- and two-compartment neighbourhoods in harvest scheduling problems including a spatial objective variable. The tested heuristics were random ascent, Hero, simulated annealing and tabu search. All methods seek better solutions by inspecting the neighbourhood solutions, which are combinations that can be obtained by changing the treatment schedule in one (one-compartment neighbourhood) or two (two-compartment neighbourhood) compartments. The methods and neighbourhoods were examined in one artificial and four real landscapes ranging from 700 to 981 ha in size. The landscapes had 608 to 900 stand compartments, and the examined planning problems had 2986 to 4773 binary decision variables. The objective function was a multi-objective utility function. The spatial objective variable was the percentage of compartment boundary that joins two compartments, both of which are to be cut during the same 20-year period. The non-spatial objectives were net incomes of three consecutive 20-year management periods and the remaining growing stock volume at the end of the third 20-year period. In another problem formulation, the total harvest of the first 20-year period was used as an objective variable together with the spatial objective. The results showed that a two-compartment neighbourhood was systematically and often clearly better than a one-compartment neighbourhood. The improvements were greatest with the simplest heuristics, random ascent and Hero. Of the four heuristics, tabu search and simulated annealing proved to be the best methods, but with a two-compartment neighbourhood the differences between methods were negligible.

Heinonen, University of Joensuu, Faculty of Forestry, P.O. Box 111, FI-80101 Joensuu, Finland E-mail: th@nn.fi
Pukkala, University of Joensuu, Faculty of Forestry, P.O. Box 111, FI-80101 Joensuu, Finland E-mail: timo.pukkala@joensuu.fi

article id 438, category Research article

Christina Lundgren. (2004). Cell wall thickness and tangential and radial cell diameter of fertilized and irrigated Norway spruce. Silva Fennica vol. 38 no. 1 article id 438. https://doi.org/10.14214/sf.438

Keywords: cell wall thickness; tangential tracheid diameter; radial tracheid diameter; tracheid dimensions; nutrient optimisation; juvenile wood

Abstract | View details | Full text in PDF | Author Info

Two Norway spruce nutrient trials were used to evaluate the effects of fertilization and irrigation on transverse tracheid dimensions. Three different treatments and a control (C) were used; daily irrigation (I), daily liquid fertilization (IL) and an annual solid fertilization (F). The nutrient optimisation was based on foliage analysis and both liquid and solid fertilization essentially comprised the same amount of nutrients but the latter was applied annually in solid form. The cell measurements; cell wall thickness, radial and tangential cell widths, were obtained using image analysis (SilviScan at CSIRO, Melbourne, Australia). Mean annual cell wall thickness was decreased by fertilization (F and IL) on both sites whereas no effect of the irrigation on wall thickness could be detected. Radial cell width was increased by treatment at Flakaliden but at Asa the effect of irrigation and fertilization was reversed when the data structure i.e. development from pith and out and annual ring width was taken into account. Tangential cell width was not significantly affected by treatment at Flakaliden. At Asa fertilization caused a small increase on tangential cell width. Ring width was positively affected by treatment and is an important factor explaining the effects on primarily cell wall thickness and radial cell width.

Lundgren, SLU, Dept. of Forest Products and Markets, P.O. Box 7060, SE-750 07 Uppsala, Sweden E-mail: christina.lundgren@spm.slu.se

Category : Discussion article

article id 536, category Discussion article

Ian Cowan. (2002). Fit, fitter, fittest; where does optimisation fit in? Silva Fennica vol. 36 no. 3 article id 536. https://doi.org/10.14214/sf.536

Keywords: survival; optimisation; growth; assimilation; nitrogen-use; water-use

View details | Full text in PDF | Author Info

Cowan, Research School of Biological Sciences, Australian National University, Canberra, ACT 0200, Australia E-mail: iancowan@bigpond.com.au

Category : Commentary

article id 528, category Commentary

Annikki Mäkelä, Thomas J. Givnish, Frank Berninger, Thomas N. Buckley, Graham D. Farquhar, Pertti Hari. (2002). Challenges and opportunities of the optimality approach in plant ecology. Silva Fennica vol. 36 no. 3 article id 528. https://doi.org/10.14214/sf.528

Keywords: models; acclimation; adaptation; optimisation; evolution; hypotheses; evaluation

Abstract | View details | Full text in PDF | Author Info

A meeting was held in Hyytiälä, Finland 10–12 April 2000 to assess critically the current challenges and limitations of the optimality approach in plant ecophysiology and botany. This article summarises the general discussions and views of the participants on the use of optimisation models as tools in plant ecophysiological research. A general framework of the evolutionary optimisation problem is sketched with a review of applications, typically involved with balanced regulation between parallel processes. The usefulness and limitations of the approach are discussed in terms of published examples, with special reference to model testing. We conclude that, regardless of inevitable problems of model formulation, wider application of the optimality approach could provide a step forward in plant ecophysiology. A major role of evolutionary theory in this process is simply the formulation of testable hypotheses, the evaluation of which can lead to important advances in our ecophysiological understanding and predictive ability.

Mäkelä, University of Helsinki, Dept. of Forest Ecology, P.O. Box 27, FIN-00014 University of Helsinki, Finland E-mail: annikki.makela@helsinki.fi
Givnish, University of Wisconsin, Department of Botany, Madison, WI 53706 USA E-mail: tjg@nn.us
Berninger, University of Helsinki, Dept. of Forest Ecology, P.O. Box 27, FIN-00014 University of Helsinki, Finland E-mail: fb@nn.fi
Buckley, Cooperative Research Centre for Greenhouse Accounting and Environmental Biology Group, and Research School of Biological Sciences, Australian National University, ACT 2601, Australia E-mail: tnb@nn.au
Farquhar, Cooperative Research Centre for Greenhouse Accounting and Environmental Biology Group, and Research School of Biological Sciences, Australian National University, ACT 2601, Australia E-mail: gdf@nn.au
Hari, University of Helsinki, Dept. of Forest Ecology, P.O. Box 27, FIN-00014 University of Helsinki, Finland E-mail: ph@nn.fi

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