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  • 101.
    Blomqvist, Lars
    et al.
    Linneaus University.
    Johansson, Jimmy
    Linneaus University.
    Sandberg, Dick
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Moisture-induced distortion of laminated veneer products.2014Inngår i: 68th Forest Products Society International Convention, Quebec City, Canada, August 10-13, 2014, 2014Konferansepaper (Annet vitenskapelig)
  • 102.
    Blomqvist, Lars
    et al.
    Linnéuniversitetet.
    Johansson, Jimmy
    Linnéuniversitetet.
    Sandberg, Dick
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Shape stability of laminated veneer products: How to decrease the negative effects of fibre deviation?2013Konferansepaper (Fagfellevurdert)
    Abstract [en]

    A shortcoming of the laminated bending process is that the products may become distorted after moulding and during use. Annually, significant financial losses have incurred in the furniture and interior design industries as a result of distorted products. In this study, we have examined the influence of deviation of fibre orientation of individual veneers on distortion of a moulded shell to find ways to improve shape stability of laminated veneer products.Ninety cross-laminated shells, consisting of 7 veneers of Birch (Betula pubescens Ehrh.) with a total thickness of 3.6 mm, were studied. The in-plane dimensions of the veneer were 400x660 mm. All the veneers were straight-grained, but to simulate deviation in fibre orientation some of the individual veneers were oriented 7 degrees relative to the main orientation of the other veneers in the laminate. Distortion was determined directly after moulding and after storage in a changing relative humidity.The results show the well-known fact that deviation of fibre orientation of the veneers in the laminate influences the shape stability of the product. The results from this study, however, also show how the placement of the abnormal veneers in the laminated veneer products influences the degree of distortions. From this basic knowledge some improvements for production of laminated veneer products were suggested.

  • 103.
    Blomqvist, Lars
    et al.
    Linneaus University.
    Johansson, Jimmy
    Linneaus University.
    Sandberg, Dick
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Veneer modification for improved formability when moulding laminated veneer products.2014Inngår i: 68th Forest Products Society International Convention, Quebec City, Canada, August 10-13, 2014, 2014Konferansepaper (Annet vitenskapelig)
  • 104.
    Blomqvist, Lars
    et al.
    Forest and Wood Technology, Linnæus University.
    Sandberg, Dick
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Johansson, Jimmy
    Linnæus University, Forestry and Wood Technology.
    Influence of veneer orientation on shape stability of plane laminated veneer products2014Inngår i: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280, Vol. 9, nr 4, s. 224-232Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    One of the most important quality aspects of a laminated veneer product is its shape stability under changing relative humidity (RH). This study aimed to establish an understanding of how the orientation of individual veneers in the laminate, i.e., orientation according to fibre orientation and orientation of the loose (the side with ‘lathe checks’) or tight side of the veneer, affects the shape stability. Three-ply laminates from peeled veneers of beech (Fagus sylvatica L.) were studied. The four types of laminate were the following: loose sides of all veneers in the same direction (cross and parallel centre ply) and loose sides of the outer veneers facing inward (cross and parallel centre ply). Four replicates of each type yielded 16 samples. The samples were exposed to RH cycling at 20% and 85% RH at 20°C, and the shapes of the samples were determined. The shape stability was influenced by the veneer orientation. Laminations with the middle veneer perpendicular to the top and bottom veneer (cross-laminated) showed the best shape stability, especially when the loose sides of the veneers were oriented the same direction. In parallel-laminated veneers, the laminates with opposite directions of the loose sides in the two outermost veneers showed the best shape stability. The major explanation of the behaviour of the laminates is that the loose side expanded more than the tight side from the dry to the humid climate, which was shown by optical 3D deformation analysis (ARAMISTM). After RH cycling, the laminates with cross plies showed visible surface checks only when the tight side was facing outwards.

  • 105.
    Blomqvist, Lars
    et al.
    Linneaus University.
    Sterley, Magdalena
    SP Technical Research Institute of Sweden, SP Wood Technology, Skellefteå.
    Sandberg, Dick
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Johansson, Jimmy
    Department of Forestry and Wood Technology, Linnæus University.
    The effect of veneer-modifcation on the bond-strength in laminated veneer products2015Inngår i: Pro Ligno, ISSN 1841-4737, E-ISSN 2069-7430, Vol. 11, nr 4, s. 43-49Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A major problem in the manufacture of three-dimensional laminated veneer products (LVP) is damage due to stretching and/or buckling of the veneer. To reduce or eliminate this problem, veneer densification or adding a strengthening layer to the veneer can be an alternative. To study how veneer modification influences the veneer-to-adhesive bond strength, three methods of modification were studied in relation to an unmodified reference veneer: (1) densified veneer, (2) veneer pre-bonded with paper and hot melt adhesive (HMA), (3) veneer pre-bonded with non-woven polypropylene (NW) fabric glued to the veneer (a) with a urea formaldehyde (UF) adhesive, (b) with a mixture of UF and polyvinyl acetate (PVAc) adhesive, and (c) with a PVAc adhesive. Densification, pre-bonding with paper, and NW with UF/PVAc adhesive mixture resulted in no or only a slight decrease in strength of the bond-line compared to the reference. NW glued with UF or PVAc adhesive showed a considerable reduction in the strength of the bond-line. The climatic cycling had no significant influence on the bond strength.

  • 106.
    Blomqvist, Lars
    et al.
    Department of Forestry and Wood Technology, Linnæus University.
    Sterley, Magdalena
    SP Technical Research Institute of Sweden, Wood Technology.
    Sandberg, Dick
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Johansson, Jimmy
    Department of Forestry and Wood Technology, Linnæus University.
    The influence of veneer modification on adhesive bond strength2014Inngår i: Proceedings of 10th Meeting of the Northern European Network for Wood Science & Engineering (WSE) / [ed] Peter Wilson, Edinburgh: Edinburgh Napier University. , 2014, s. 150-155Konferansepaper (Fagfellevurdert)
  • 107.
    Bomark, Peter
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Towards better understanding of forestry-wood chain simulation through visualization and interactivity2014Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Simulation studies performed on the forestry-wood chain trend towards either complicated calculations on large data-sets, statistical exercises on endless production data, optimisations on specific sub domains, or a combination of the above. The studies are often presented through graphs showing how scalars such as value, profit, or yield fluctuate when parameters of the simulation model are tweaked.The simulation models are usually stringed together from a series of operations performed in various software packages, scripts, macros and purpose written code. Reusing code from past studies is common practise, either as part of the new program, or by simply running the data through an executable and parsing the results in the next operation. Since there is no framework built around the operations, changing the input data will often mean that you have to start again from the top, guiding the data through all the different steps manually. To make things worse; the simulation model, the experiment code, and the analysis code tend to be mixed together making validation and verification difficult.Keeping track of how each operation impacts the result is difficult, and understanding how different parameters interact with each other on a system-wide basis is hopeless.Despite already being complex, most studies omit important aspects of the system they are modelling. Processing time, stochastic behaviour, separation of experimental data from model data, and so on. At the same time, if the fidelity of the simulation models continue to increase, they will eventually become too unwieldy to comprehend.Despite this, simulation is one of the most important tools available when trying to improve the forestry-wood chain, and the results that have been produced through the use of simulation are awe-inspiring. With proper tools and methodology, the integrated simulation model of the forestry-wood chain is not far away.This document is an attempt at finding tools that help design understandable simulation models of the complex systems in the forestry-wood chain. The hypothesis is that visualisation and interactivity can give alternative feedback on simulation models, providing better foundations for decisions than scalar measures like profit or yield.

  • 108.
    Bomark, Peter
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Evertsen, Gunn
    Northern Research Institute.
    Brox, Ellen
    Northern Research Institute.
    Hirche, Johannes
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Datavetenskap.
    Yliräisänen-Seppänen, Pia
    Rovaniemi University of Applied Sciences.
    A prototype social learning platform for children with diabetes type 12012Inngår i: Proceeding of the 16th International Academic MindTrek Conference 2012: Envision Future Media Environments, New York: Association for Computing Machinery, Inc. , 2012, s. 211-213Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Children diagnosed with diabetes type 1 are bombarded with information and have a hard time understanding it all. Existing information material consists mostly ofbrochures and textbooks, giving little opportunity for testing and trial-and-error without consequences. A social platform with learning games gives the children an opportunity to experiment and find peer support, which is important for coping with a life long disease.

  • 109.
    Bomark, Peter
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Hirche, Johannes
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Datavetenskap.
    Hagman, Olle
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Colour visualisation of real virtual timber using image quilting2015Inngår i: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 73, nr 6, s. 837-839Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    When presenting images of wood obtained through x-ray computed tomography to an audience inexperienced in interpreting radiological images, explaining the correspondence between mass attenuation and features of wood could be time consuming and confusing. Realistically colourised attenuation images might be a suitable option in order to facilitate understanding of the images. Mass attenuation and colour of wood does not have a simple correlation, so naive grey-scale to colour conversion does not work. This paper describes how image quilting can be used to transfer colour information from a image pair where both mass attenuation and colour is known to a target mass attenuation image. An example of this method applied on scots pine shows that it is capable of retaining the major structures of wood, such as year rings and knots. The method could allow for easier understanding of simulation studies where logs scanned using x-ray computed tomography are virtually sawn.

  • 110.
    Boonstra, M.J.
    et al.
    Plato International AV, Arnhem.
    Blomberg, Jonas
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Semi-isostatic densification of heat-treated radiata pine2007Inngår i: Wood Science and Technology, ISSN 0043-7719, E-ISSN 1432-5225, Vol. 41, nr 7, s. 607-617Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Semi-isostatic densification is a useful method to increase the density and to improve the mechanical properties of fast-grown softwood species like radiata pine. A major disadvantage of this method is the almost complete recovery of the original dimensions when densified wood is exposed to moisture. Heat treatment improves the dimensional stability of wood and might be a useful method to prevent this shape-recovery after densification. However, no or only a limited effect on the shape-recovery was found when densified radiata pine was exposed to moisture.

  • 111.
    Breinig, Lorenz
    et al.
    Forstliche Versuchs- und Forschungsanstalt Baden-Württemberg (FVA).
    Berglund, Anders
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Grönlund, Anders
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Bruechert, Franka
    Forstliche Versuchs- und Forschungsanstalt Baden-Württemberg (FVA).
    Sauter, Udo
    Forstliche Versuchs- und Forschungsanstalt Baden-Württemberg (FVA).
    Effect of knot detection inaccuracy on value recovery improvement when using a CT log scanner for sawing control2013Inngår i: Forest products journal, ISSN 0015-7473, Vol. 63, nr 7-8, s. 263-274Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Roundwood scanners utilizing X-ray computed tomography (CT) provide the information required for individual log-sawing optimization. However, errors in the automated detection of quality-relevant internal wood features for sawing control may lead to improper log positioning at breakdown, impairing the realization of value recovery potential. It is thus of interest to have an estimation of the impact of feature detection errors on the performance of sawing optimization. A sensitivity analysis was conducted to quantify the effect of errors in knot detection on a breakdown optimization by adjustment of log rotation. Therefore, sawing simulations were performed with the geometric descriptions of log shape and internal knots extracted from the CT scans of 57 Norway spruce (Picea abies (L.) Karst.) logs. Three types of artificially set knot description errors were tested under different pricing and product scenarios, each in different magnitudes as systematic or random error. Errors in knot diameter were found to have the greatest impact for both systematic and random errors. The effect of errors in dead knot border radial position was less pronounced but still substantial for higher error levels, while errors in knot rotational position could be neglected even for the highest magnitudes of error tested. The assumed price differentiation between product qualities had a major influence on the impact of the errors. It could be observed that with errors of higher magnitudes than those reported for present knot detection algorithms, an improvement in value recovery compared with outer-shape–based optimization still resulted in the simulated rotation optimization.

  • 112.
    Breinig, Lorenz
    et al.
    Forest Research Institute of Baden-Württemberg, 79100 Freiburg.
    Broman, Olof
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Brüchert, Franka
    Forest Research Institute of Baden-Württemberg, 79100 Freiburg.
    Becker, Gero
    Institute of Forest Sciences, University of Freiburg.
    Optimization potential for perception-oriented appearance classification by simulated sawing of computed tomography-scanned logs of Norway spruce2015Inngår i: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280, Vol. 10, nr 4, s. 319-334Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Wood, as a natural material, has favourable properties in both technical and aesthetic aspects. Due to its inherent variability,production of high-quality sawn timber demands adequate control of log conversion, which is feasible with computedtomography (CT) log scanning. Existing appearance grading rules for sawn timber might not fully reflect people’s visualperception of wood surfaces, and therefore, an alternative, more perception-oriented appearance classification could bebeneficial. An appearance classification of sawn timber based on partial least squares discriminant analysis (PLS-DA) ofknot-pattern variables was developed and tested. Knot-pattern variables derived from images of board faces were used intraining PLS-DA models against an initial classification of the board faces previously established by aid of cluster analysis.Virtual board faces obtained from simulated breakdown of 57 CT-scanned Norway spruce logs were graded according tothe developed classification. Visual assessment of the grading results indicated that the classification was largely consistentwith human perception of board appearance. An initial estimation of the potential to optimize log rotation, based on CTdata, for the established appearance grades was derived from the simulations. Considerable potential to increase the yield ofa desired appearance grade, compared to conventional log positioning, was observed.

  • 113.
    Breinig, Lorenz
    et al.
    Forest Research Institute of Baden-Württemberg, 79100 Freiburg.
    Leonhart, Rainer
    Institute of Psychology, University of Freiburg.
    Broman, Olof
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Manuel, Andreas
    University of Freiburg, Institute of Forest Sciences, University of Freiburg.
    Brüchert, Franka
    Forest Research Institute of Baden-Württemberg, 79100 Freiburg.
    Becker, Gero
    Institute of Forest Sciences, University of Freiburg.
    Classification of wood surfaces according to visual appearance by multivariate analysis of wood feature data2015Inngår i: Journal of Wood Science, ISSN 1435-0211, E-ISSN 1611-4663, Vol. 61, nr 2, s. 89-112Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Its natural aesthetics make wood an attractivematerial for construction and design. However, there is nodetailed understanding of the relationships between humanperception of the appearance and measurable features ofwood surfaces that could be used for controlling sawntimber production. This study investigated whether woodsurfaces can be classified according to their visualappearance on the basis of wood feature measurements.Cluster analysis was used to discover a classification basedon a set of feature pattern variables in a sample of 300softwood floorboards. A finely graded visual appearancesorting provided a reference. Discriminant analysis wasapplied to identify the relevant variables from the tested setand to assess predictability of the classification. The resultsindicated that visual appearance sorting could be approximatedquite well by the variable-based classification afterpregrouping according to board position in the log.Ambivalent results were obtained for group predictionwithin the validation sample. While for boards from somegroups prediction was mostly or entirely correct, boardsfrom other groups were largely misclassified. An effect ofthe available sample was one of the surmised causes,making repetition of the analysis based on a larger sample adesirable focus of further research.

  • 114.
    Broman, Olof
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Aesthetic properties in knotty wood surfaces and their connection with people's preferences2001Inngår i: Journal of Wood Science, ISSN 1435-0211, E-ISSN 1611-4663, Vol. 47, nr 3, s. 192-198Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    For wood products that contain visible wood surfaces it is important to be able to describe, measure, and communicate the aesthetic properties desired. The aims of this investigation were to shed light on how people's preferences toward different wood appearances containing knots can be described and to create a better understanding of how to measure those preferences. A total of 215 persons from Sweden with different backgrounds were interviewed as to their preferences for 10 Scots pine wood surfaces containing knots. Their impressions and preferences were documented by a questionnaire with 54 questions and analyzed by a principal component analysis. A thorough description of what people see and value in a wood surface with knots is given in the body of the text. People's preferences are affected by a balance between two main properties: the degree of harmony and activity, and the importance of avoiding a state of disharmony when composing wood surfaces. When investigating people's preferences toward a knotty wood appearance, 13 of 54 questions proved to be important. Three questions detect the final assessment, and four describe the reasons for the final assessment. Finally, six questions describe the blend of wood properties in a more objective way and are to only a minor extent connected with the final assessments.

  • 115.
    Broman, Olof
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Attitudes toward Scots Pine wood surfaces: a multivariate approach1995Inngår i: Mokuzai Gakkaishi, ISSN 0021-4795, E-ISSN 1880-7577, Vol. 41, nr 11, s. 994-1005Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Wood as a material has inherent aesthetic features which, rightly used, give the final product competitive advantage over other materials. The aim of this investigation was to find relevant questions to ask when measuring people's preferences for different looks of wood and to reveal the relationship between the mixture of features in a wood surface and people's attitudes. A total of 344 persons participated in the study judging the look of 16 wood surfaces made of Scots pine (Pinus sylvestris). Their impressions and feelings were analysed by three multivariate methods; correlation, principal component and partial least squares analysis. The study shows that it is possible to measure people's feelings for different looks of wood surfaces. The results show that there are differences in people's judgements for surfaces with knots and without knots. The results also show that there are about 15 questions needed to detect people's preferences for a wood surface.

  • 116.
    Broman, Olof
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Means to measure people's attitudes towards wood1995Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Wood is a material with many faces. It evokes feelings in us that no artificial material can do. Wood has inherent aesthetic features which, rightly used, give the final product competitive advantage over other materials.In this thesis people's feelings and preferences for Scots pine (Pinus sylvestris) wood surfaces have been examined. It comprises a qualitative study of what people see and evaluate in wood and two separate investigations aiming at quantifying people's preferences for wood. Those two investigations were analysed by multivariate techniques.The results show that people prefer different blends of wood features. There are two qualitative differences that are of importance for people's impression and valuation of wood: The overall blending of wood features and divergent features that mismatch in a surface. It was found that divergent features are more important than the overall mixture of features. But if there are no defects that mismatch, the overall mixture will then be the key to a person's appreciation of a wood surface. Other results from the qualitative study are a map of wood features that people see and a description of the phenomenon Attitudes Toward Wood divided into properties and aspects.The quantitative studies show that it is possible to measure people's attitudes toward wood by a questionnaire technique. The results also show that there are differences in people's judgements for surfaces with knots and without knots and that there are about 10 questions needed for detecting people's preferences for wood. A wood surface that people prefer should have at least one of the following characteristics:- Have a fresh look - Be restful- Be in harmony - Have an eventful look- Be interesting to look at - Not look like an imitation- Be elegant - Be imaginative- Be exciting to look at - Not be gaudyTwo interviewing methods were compared. The first method used wood surfaces and the second used computer images with the same wood surfaces applied to an example product, a kitchen cabinet. The result shows that the two methods are comparable and useful.

  • 117.
    Broman, Olof
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Means to measure the aesthetic properties of wood2000Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Wood is a biological material with inherent aesthetic properties which can give the final product a competitive advantage over other materials. In this thesis, people’s feelings and preferences for Scots pine (Pinus sylvestris) wood surfaces have been examined. The main objectives of this thesis are to develop methods for measuring people’s preferences toward different looks of wood and to connect the subjective preference data with objective measurements of wood features. It comprises both qualitative and quantitative methods for collecting preference data. Two projection methods, PCA and PLS, were used to analyze the quantitative studies. Interviews made clear that people prefer different blends of wood features. There are two qualitative differences that are of importance for people's impressions and valuations of wood: The overall blend of wood features and divergent features that mismatch in a surface. It was found that divergent features are more important than the overall mixture of features. But if there are no defects that mismatch, the overall mixture will then be the key to a person's appreciation of a wood surface. Wood surfaces should stimulate people's interest and be fresh looking. A clear surface is naturally rather harmonious, elegant and easy to look at. On the other hand, a clear surface should be stimulating to look at, should be exciting and it should not look like an imitation. Knotty surfaces usually are less harmonious. Therefore, questions about harmony, easiness to look at and balance are of importance. Just as for clear surfaces, a knotty surface should also stimulate people's interest, have a fresh look, be exciting and stimulating to look at. The quantitative studies show that it is possible to measure people’s preferences toward wood by a questionnaire technique. The results also show that there are differences in people’s judgments for surfaces with knots and for those without knots. There are stronger connections between questions regarding the overall impression and the final assessment than there are for detailed questions regarding certain wood features. Thirteen questions were pointed out as relevant to use with interviews. Two interview methods were compared. The first method used wood surfaces and the second used computer images with the same wood surfaces applied to an example product, a kitchen cabinet. The results show that the two methods are comparable and useful. It was shown that it is possible to some extent to connect subjective preference data with objective wood feature measurements. Results show that a lot of wood feature measurements are needed and that it is a multivariate problem. Concerning the measurements, it seems easier to find features that negatively affect people’s liking than to find the opposite. Among the most important variables were those that detect different kinds of feature distribution over a wood surface, and especially those variables that detect a deviation in center of gravity. Increased knowledge about people’s preferences for the aesthetic properties of wood will lead to a better understanding of which wood features should be measured and controlled in the future.

  • 118.
    Broman, Olof
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    The measurement of wood features in knotty Scots pine wood surfaces and the connection with people´s preferences2003Inngår i: Developments in image processing and scanning of wood: selected and edited papers from the 4th International Conference on Image Processing and Scanning of Wood, Mountain Lake, Virginia, USA, 21 - 23 August, 2000, 2003Konferansepaper (Fagfellevurdert)
  • 119.
    Broman, Olof
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    The measurement of wood features in knotty Scots pine wood surfaces and the connections with people's preferences2000Inngår i: Developments in image processing and scanning of wood: selected and edited papers from the 4th International Conference on Image Processing and Scanning of Wood, Mountain Lake, Virginia, USA, 21 - 23 August, 2000 / [ed] Earl D. Kline, Virginia Tech , 2000Konferansepaper (Fagfellevurdert)
    Abstract [en]

    For wood products that contain visible wood it is important to be able to describe the aesthetic properties desired, to measure and communicate them. The aim of this investigation was to shed light on the connections between people's preferences and the physical blend of wood features measured in digital images of Scots pine wood surfaces.  A total of 215 persons from Sweden with different backgrounds were interviewed regarding their preference for ten Scots pine wood surfaces containing knots. Their impressions and preferences were documented by a questionnaire. Many texture features (140 variables) were extracted from grayscale images of the wood surfaces and the connections with the preference data were modeled by partial least square analysis. Results from detail questions concerning what people thought about specific wood features were used as guidelines for the variable extraction. Prediction models for the preference questions were established and reported. For each prediction model, the 30 most robust wood feature variables were sorted out before the modeling. The results show that the wood feature variables varied in importance and all but one model was significant. The most important variables were those that detect different kinds of feature distribution over a wood surface and especially those variables that detect a deviation in center of gravity. The results illuminate the use of subjective preference data regarding the aesthetic properties of wood and give rise to some ideas of how to implement them in a production process.

  • 120.
    Broman, Olof
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Two methods for measuring people's preferences for Scots pine wood surfaces: a comparative multivariate approach1996Inngår i: Mokuzai Gakkaishi, ISSN 0021-4795, E-ISSN 1880-7577, Vol. 42, nr 2, s. 130-139Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The aim of this investigation was to compare two methods for measuring people's attitudes toward different appearances of Scots pine (Pinus sylvestris L.) and to determine relevant questions to ask them. Interviews were made at a fumiture exhibition in Sweden, and people were asked to evaluate different appearances of wood used in a kitchen cabinet. The first method used plain wood surfaces, and the second method used computer images of the same wood surfaces used in a kitchen cabinet.The results showed that it is possible to measure people's feelings and preferences for wood and that people's preferences for different appearances of wood are not affected if their judgements are based on computer images or if they are based on real wood surfaces. There are about ten questions needed to describe people's attitudes towards wood. A wood surface that people prefer should :-Have a fresh appearance -Be restful-Be in harmony -Have an eventful appearance-Be interesting to look at -Not look like an imitation-Be elegant -Be imaginative-Be exciting to look at -Not be gaudyThis study was the third part in a major project "price sensitivity for wood features".

  • 121.
    Broman, Olof
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Visual impression of features in Scots pine wood surfaces: a qualitative study1995Inngår i: Forest products journal, ISSN 0015-7473, Vol. 45, nr 3, s. 61-66Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Wood has inherent aesthetic features which give the final product competitive advantage over other materials. The goal of this study was to describe and create understanding of people's feelings and attitudes toward wood in order to develop quantitative studies in the future. Ten persons with different backgrounds were interviewed regarding 27 wood surfaces made of Scots pine. Their impressions and feelings were documented and analyzed with a qualitative method. The result is a map describing what features people see in wood. Depending on the mixture of wood features the impression will differ. Interviews made clear that people prefer different blends of wood features. There are two qualitative differences that are of importance for people's impression and valuation of wood. First there is the overall blending of wood features and second, if there are divergent features that mismatch in the surface. The latter factor can be divided into two ; - Distinguishing natural defects. - Technical defects made by machine or the carpenter. It was found that divergent features are more important than the overall mixture of features. But if there are no defects that mismatch, the overall mixture will then be the key to a person's appreciation of a wood surface. Wood features can be seen as input data for interpretation and valuation by a person and the impression of sight should be seen as output data from the valuation process. Input data are quite objective and can be measured automatically by scanning techniques. Interviews have to be used to measure the subjective output data. The results of this investigation point toward useful queries or measurements to be made in future qualitative or quantitative studies.

  • 122.
    Broman, Olof
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Fredriksson, Magnus
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik.
    Wood material features and technical defects that affect the yield in a finger joint production process2011Konferansepaper (Fagfellevurdert)
    Abstract [en]

    A cost efficient process is the goal for every production process. In wood manufacturing, each step in the process may affect the material utilization and the cost efficiency. Wood as a material has got high diversity in its inherent features and the different manufacturing steps must be able to handle this. In most end products the proportion of the raw material cost is high. Thus, material utilization and cost efficient processes are of great importance. The overall aim of the project was to study the potential and problems in manufacturing production processes in terms of material utilization efficiency. A production process of finger jointed bed sides for IKEA was chosen as a study case and its chain of production units are; a sawmill for plank production, a finger joint company producing components and finally a furniture company that produce the end product. The aim of this article is to describe the impact of different raw material and what wood and technical defects that affect the total yield of a manufactured product. In total 177 logs of three different log types were tested; butt logs, intermediate logs and fresh knot logs. The quality of the wood material was detected and measured by aid of 3D-scanning and X-ray (logs), FinScan (planks), and WoodEye (planks/components) and manual inspection of the final products. With a full traceability data collection the quality of the test material was followed through all steps in the manufacturing chain. The result show differences between log types in down-grade causes, reject volume and the final yield of accepted products. Also, the test material showed high levels of reject with non-biological background which suggest the need of technical improvements in the finger joint and the furniture manufacturing process. The intermediate log group showed overall the best result.

  • 123.
    Broman, Olof
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Fredriksson, Magnus
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Wood material features and technical defects that affect yield in a finger joint production process2012Inngår i: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280, Vol. 7, nr 4, s. 167-175Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A cost efficient process is the goal of all production, and each manufacturing step affects the material utilization and cost efficiency. There is high diversity in the inherent features of wood, and manufacturing steps must be able to handle this. The overall objective was to study the potential and problems in manufacturing production processes in terms of material utilization efficiency. The production of finger jointed bed sides was chosen as a study case, where the chain of production units are the sawmill, finger joint plant and furniture plant. This article describes the impact of raw material and wood defects that could affect the total yield. A total of 177 logs of three types were tested: butt, intermediate and fresh knot logs. The test material quality was detected and measured through all steps in the manufacturing chain. The results show differences between log types in down-grade causes, reject volume and final yield. Also, the test material showed high levels of defective components with process-related defects, which suggested the need for technical improvement in the manufacturing process. The intermediate log group showed the overall best result.

  • 124.
    Broman, Olof
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Grönlund, Anders
    The end-users´ requirements for the aesthetical features of scots pine wood1996Inngår i: Connection between silviculture and wood quality through modelling approaches and simulation softwares: Second Workshop, Berg-en-Kruger, Kruger National Park, South Africa, August 26-31, 1996 : proceedings / [ed] Gérard Nepveu, Nancy: INRA Editions, 1996, s. 343-352Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Wood has inherent aesthetic features which can give the final product competi­tive advantage over other materials. It is therefore important for the forest products industries to take advantage of those features of wood that have great influence on customers' choice of product. It is the final consumer's willingness to buy a product that is the motive power for the whole production process. Today, the forest products industry is not using any scientific method in order to utilize the aesthetic features of wood. Therefore methods to measure people's preferences for different wood features and also methods to measure these features in an objective way are needed.We have in an earlier study shown that it is possible to measure people's attitudes toward wood by a questionnaire technique. The results show that people prefer different blends of wood features. There are two qualitative differences that are of importance for people's impression and valuation of wood: The overall blending of wood features and divergent features that mismatch in a surface. It was found that divergent features are more important than the overall mixture of features. But if there are no defects that mismatch, the overall mixture will then be the key to a person's appreciation of a wood surface. In a new study, we have started to measure the different wood features in an objective way and developed statistical models of the relationship between the objective parameters and people's subjective preferences for different wood surfaces made of Scots pine (Pinus sylvestris). In this first attempt we have made very simple manual measurements of parameters such as knot size, knot type, knot shape and distribution of knots over the surface.The statistical analyses show that it is difficult to find any significant relation­ships between people's subjective preferences and the simple objective para­meters we have measured. It is evident that more sophisticated measure­ment tech­nique is needed. We must be able to measure parameters such as colour, grain pattern etc. Therefore we will use colour camera technique in future studies.

  • 125.
    Broman, Olof
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Grönlund, Anders
    Nordvik, Enar
    Lundahl, Carl Gustav
    Estetiska kvaliteter och skillnader i preferenser för limfog: en jämförelse mellan två intervjumetoder2008Rapport (Annet vitenskapelig)
    Abstract [sv]

    Den produktgrupp som här studerats är limfog för Gör-Det-Själv-marknaden. Limfog är en vanlig produkt som konsumenter köper styckevis och där träets estetiska blandning av träegenskaper kan vara av betydelse för ett aktivt val eller köp av kunden. Projektets övergripande mål var att studera vanliga konsumenters olika känslighet (smakprofiler) för olika utseenden på trä. Huvudmålet med studien var att jämföra två metoder för preferensmätning; dels användandet av riktiga träytor (limfog) och dels digitala bilder av desamma för rangordning av produktalternativ. För att validera användbarheten av de båda metoderna jämfördes deras rangordningsresultat. Ett delmål med studien var att studera skillnader mellan preferenser för limfog som producerats enligt alternativa produktionssätt med traditionellt producerad limfog. Femton personer intervjuades i två omgångar. I den första intervjun fick personerna rangordna 11 limfogsytor med hjälp av datorbilder och en webapplikation. I den andra intervjun två veckor senare fick samma personer rangordna samma limfogsytor fast nu med riktiga träytor. Resultaten från intervjuerna visar att de båda metoderna gav likvärdiga resultat. Det fungerade bra att använda digitala bilder och utföra preferensstudier via utvecklad web-applikation. För båda metoderna gällde att 11 stycken produktalternativ var på gränsen till för många att ta ställning till för de intervjuade personerna. Detta gällde båda intervjumetoderna. Bildernas kvalitet visade sig vara viktigt och de små skillnader i rangordningsresultat mellan de två intervjumetoderna kan till viss del förklaras av bristande återgivning av färgnyanser. Metoden att rangordna de verkliga limfogsskivorna fungerade mycket bra. Principen att välja ömsom bäst och sämst och kontinuerligt plocka bort valda produktalternativ fungerade bra. Följande estetiska kvalitetsskillnader visade sig vara viktiga för intervjupersonerna: En jämn fördelning av kvistar över ytan (limfogen) tillika blandning av kvistutseende är viktigt för helhetsintrycket. Märgstråk upplevdes starkt negativt då de ses som streck i ytan, en artefakt. Detta gäller också hög grad av randighet som upplevdes negativt. Detta kan orsakas av splint-/kärnvedsvariationer, speciellt när limfogen producerats med låg lamellbredd. Negativt var också tjurvedsstråk som orsakar randighet i en yta, vilket stör den visuella balansen och harmonin. Den limfog som producerats inom ramen för en ny högutbytesstrategi rankades högre än den traditionellt tillverkade limfogen som var inköpt. Detta kan förklaras främst av en hög grad av färska kvistar (ej svarta och eller döda kvistar), som kommer sig av valet av råvara. Råvaran utgjordes av klentimmer medan råvaran till den traditionellt tillverkade limfogen kom från plank med ursprung från osorterat timmer. Slutsatsen är att för limfog så har valet av råvara minst lika stor betydelse än produktionssätt (lamellbredd, koniska lameller etc) för det estetiska uttrycket och kundtillfredsställelse.

  • 126.
    Broman, Olof
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Nordvik, Enar
    Fjellner, Bengt-Arne
    Means for measuring people's preferences for visual wood with aid of Internet2006Inngår i: Wood resources and panel properties :: Conference Proceedings ; Valencia, Spain, 12-13. Juni 2006 / [ed] Joris Van Acker;, AIDMA , 2006Konferansepaper (Fagfellevurdert)
    Abstract [en]

    It is of interest to study and analyse the consumer market for visual wood so as to produce the right "look" of wood to the right product and the right group of customer. The choice of wood quality to a certain product is often decided at the production site without good information of people's sensitivity (taste profiles) for different blending of wood features. Today, regarding the issue of wood quality, there are no established techniques for detecting people's taste profiles.The aim of the work has been to develop a method for preference studies where visible wood is in focus. The aim was also to present interview results showing differences in acceptance among interviewed people just to persuade the readers about the usability of the methodology.In this investigation only wood floors of parquet type have been examined. Only one room type has been used. The interior was changed over time to study possible affect on parquet flooring preferences. About 50 persons participated in the study and they answered three times each during the development process.The interview concept is interactive and self instructive to measure preferences of different appearances of wood (in this study floor). The same room is shown but with different wood flooring and the floors is ranked with aid of paired comparison. When the ranking is completed, questions with both open and given answer alternatives are asked, just to get a description of the cause of preferences.Principal Component Analysis together with simple statistics was used to envisage the reader about the usability of the method. Perhaps the most important results of the research is that it is possible to measure what people prefer and to a certain extent why. Groups of peoples with different taste profiles can be found even if the number of interviewed people was small. The different wood species was described in words of the interviewed people, which of course from a wood producing company view, can be valuable in a market communication situation.

  • 127.
    Broman, Olof
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Nordvik, Enar
    Fjellner, Bengt-Arne
    Metod för mätning av människors preferenser för synligt trä med hjälp av Internet2003Rapport (Annet vitenskapelig)
    Abstract [sv]

    Detta utvecklingsarbete är finansierat av Svenskt Trä och arbetet faller inom två prioriterade FoU områden, synligt trä och marknad. Det är av intresse att studera och analysera marknaden för synligt trä för att på så sätt producera rätt träutseende till rätt produkt och till rätt kund. Val av träkvalitet till en produkt bestäms alltför ofta i produktionsledet utan god information om känslighet för olika blandningar av träegenskaper (smakprofiler) bland sina tänkta slutkunder. Det finns idag ingen etablerad teknik för och kunskap om hur man kan mäta folks preferenser för olika träutseenden. Målet har varit att utveckla en metod för preferensstudier där synligt trä står i fokus och som ska kunna användas av företag och branschorganisationer. Målet är också att presentera de skillnader i tycke och smak som råder bland de intervjuade personerna, dels för att verifiera tidigare resultat och föreslagna metoder och dels för att visa på metodens möjligheter så att den kan utvecklas vidare till att bli ett användbart verktyg för marknadsstudier. I denna undersökning har enbart utseenden på trägolv av parkettyp studerats och endast ett visningsrum har använts dock med förändring av dess utseende och möblering under studiens gång. Ett 50-tal personer har deltagit och svarat tre gånger var under utvecklingsprocessen. Frågorna har förbättrats och rummets utseende har varierats. Förbättringsarbetet fortgår och det är snart dags att offentliggöra länken så att fler har möjlighet att delta. Fler exempelprodukter kommer att studeras. Ett konkret resultat av FoU arbetet hittills är den mötesplats på nätet http://trasmak.tt.luth.se/, som utvecklats för att mäta preferenser för olika utseenden på trä. Intervjukonceptet är självinstruerande och interaktivt där de intervjuade svarar på frågor som rör deras visuella intryck och trätexturernas utseende. Det kanske viktigaste resultatet av FoU arbetet är att det går att mäta vad folk föredrar och till viss del varför. Metoden bygger på att man rangordnar bilder av ett och samma rum men med olika trägolv med hjälp av parvis jämförelse. När rangordningen är gjord ställs frågor med både öppna och fasta svarsalternativ för att få en beskrivning av orsaken till personens val. Principal Component Analysis, PCA tillsammans med enkla tabellsammanställningar har använts med framgång för att beskriva resultaten av intervjutesterna. Grupper av olika smakriktningar kan ses även om testpersonerna var få. De olika träslagens utseende har beskrivits i ord av de intervjuade vilket kan vara värdefullt för en fullgången marknadskommunikation i träförädlingskedjan.

  • 128.
    Broman, Olof
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Nyström, Jan
    Oja, Johan
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Effektiv produktion av golvprodukter med krav på estetiska egenskaper2007Rapport (Annet vitenskapelig)
    Abstract [sv]

    Trä används i många tillämpningar där träet är synligt och där råvarans estetiska egenskaper därför är mycket. Exempel på sådana tillämpningar är produkter är golv och paneler. I detta projekt har produktionsprocessen för solida furugolv studerats, det vill säga hela kedjan från sortering av stockar till slutkonsumenters preferenser. Samarbetspartners i detta FoU- projekt har varit SCA -Bollsta sågverk, Norrlands Trä AB, SP Trätek och LTU - Träteknologi, Skellefteå. Syftet med projektet har varit att demonstrera hur man med hjälp av modern marknadsanalys, modern, industriellt implementerad mätteknik och avancerade sorteringsalgoritmer kan effektivisera produktionen av kundanpassade produkter med krav på estetiska egenskaper. Ett delmål var att undersöka alternativa utseendekvaliteter till dagens produktion av golvträ. Den genomgående metoden har varit att mäta och dokumentera råvarans egenskaper genom hela processen från stock till färdig produkt. En lättanvänd interaktiv databas har utvecklats inom ramen för projektet och använts för simulering av alternativa sorteringar av råvara avsedd för golvproduktion. Kopplat till databasen har även ett visualiseringsverktyg utvecklats. Detta gör det möjligt att direkt kunna se resultatet av simuleringarna i form av digitala golvytor. Utöver resultat i form av utvecklad databasgränssnitt, visualiseringsverktyg och verktyg för konsumentudersökningar så har projektet visat på intressanta resultat vad gäller både produktions och marknad. Resultatet av databassimuleringarna visar att man genom att förändra sorteringsstrategin och sortera stockarna baserat på information från en röntgenmätram helt kan undvika utsortering i råsorteringen, minska utsorteringen i justerverket med 25% (från tolv till nio procentenheter) och ändå producera en golvråvara med samma estetiska egenskaper som tidigare. Som ett alternativ till den ursprungliga golvråvaran har även en ny golvråvara definierats. Preferensstudier i både Sverige och Norge visade att konsumenternas tyckte bättre om den nya kvaliteten än den utsprungliga. Samtidigt gjorde denna nya golvråvara det möjligt att helt undvika utsortering i både råsortering och justerverk och samtidigt öka den tillgängliga golvråvaran med 27% (från 30 till 38 procentenheter).

  • 129.
    Broman, Olof
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Nyström, Jan
    Oja, Johan
    Modelling the connection between industrially measured raw material properties and end user preferences: Part 2. Results from preference studies2008Inngår i: Connection between Forest Resources and Wood Quality: Modelling Approaches and Simulation Software. IUFRO Working Party 5.01.04 Wood Quality Modelling, June 8. - 14, Koli, Finland / [ed] H. Peltola, 2008Konferansepaper (Annet vitenskapelig)
  • 130.
    Broman, Olof
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Wixe, David
    LTU Skellefteå, Träteknologi.
    Grönlund, Anders
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Oja, Johan
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Råvarustyrning för materialeffektiv produktion av limfog: En studie utförd vid Norrfog AB2011Rapport (Annet vitenskapelig)
    Abstract [sv]

    Norrfog AB i Malå tillverkar limfogskivor i olika kvaliteter, bland annat till gör-det-själv- (GDS)-limfog, möbelfog och IKEAs hyllkoncept Ivar. Då Norrfog planerar att öka sin producerade volym av limfog ökar behovet av en effektiv styrning av rätt råvara till rätt slutprodukt. Samtidigt stiger råvarupriserna och det blir allt viktigare att maximera volyms- och värdeutbytet. Vid tidpunkten för studien: Norrfog AB köper klena furustockar och försorterar stockarna i diameterklasser med hjälp av en 2D-mätram. Ingen sortering sker på stocktyp och därmed blandas rotstockar, svartkviststockar och friskkviststockar. Stockarna sågas med en 2ex postning till plankor som efter torkning kapas upp till komponentlängder som därefter klyvs till färdiga lameller för limfogsproduktion. Huvudsyftet med detta projekt var att undersöka möjligheterna att styra rätt kvalitet av timmer till rätt slutprodukt; Ivarhyllan, GDS-limfog och möbelfog samt för- och nackdelar med att införa ett alternativt sågsätt – genomsågning. Inom ramen för studien fanns följande forsknings- och utvecklingsfrågor: •Stocklängdens betydelse för volymutbytet av limfog? •Stocktypens betydelse för kvaliteten på producerad limfog? •Går det att hitta rätt typ av stockar till en specifik produkt redan vid timmerplanen med hjälp av befintlig 2D-mätram och förbättrar 3D eller röntgen-skanning denna klassificering av stockar? •Finns det ett motstånd till fingerskarv bland konsumenter och vad anses vara ett önskvärt utseende på en träyta av limfog? Studien visar att den stocktyp som gav den bästa kvaliteten var friskkviststockarna, men även de stockar som sorterades som svartkvistiga visade sig innehålla mestadels friska kvistar i de aktuella timmerdimensionerna. Ett tydligt resultat var att rotstockar innehöll den lägsta kvaliteten med för många och/eller för stora svarta kvistar och det visade sig vara lämpligt att om möjligt sortera bort dessa stockar för att såga dessa separat till produkter med lägre krav på kvalitet. Sorteringsalgoritmer för olika mättekniker för timmer speciellt anpassade för att maximera utbytet kvalitet 1 i den färdiga limfogen testades. Med befintlig 2D-mätram sorterades 81 % av rotstockarna bort och med röntgenmätning ökade andelen bortsorterade rotstockar till 98 %. Ett viktigt resultat var att genomsågning gav i snitt 13 % högre volymutbyte än 2ex-sågning och att korta stockar gav ökat volymutbyte jämfört med fullängdsstockar. En separat undersökning angående skivornas utseende visar att fingerskarvade limfogskivor är något konsumenten kan tänka sig, så länge färgskiftningarna mellan lamellerna är små. Stora färgskiftningar och små svarta kvistar var det som respondenterna rankade som minst tilltalande för alla skivor oavsett fingerskarv eller inte.

  • 131.
    Brox, Ellen
    et al.
    Northern Research Institute.
    Evertsen, Gunn
    Northern Research Institute.
    Bomark, Peter
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Hirche, Johannes
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Datavetenskap.
    Yliräisänen-Seppänen, Pia
    Rovaniemi University of Applied Sciences.
    User centric social diabetes game design for children2012Inngår i: Proceeding of the 16th International Academic MindTrek Conference 2012: Envision Future Media Environments, New York: Association for Computing Machinery, Inc. , 2012, s. 291-293Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Children recently diagnosed with diabetes type 1 require lots ofinformation and feel scared, alone and different. Most of theexisting educational material is on paper. Games with relevantlearning content are mainly small minigames in English. There isa need for more material with a focus on user needs, particularlylearning–by-doing material. Peer support is known to beimportant for this user group. We present a concept for a sociallearning game that is engaging and fun for diabetic children.

  • 132.
    Brunow, G.
    et al.
    University of Helsinki.
    Karlsson, Olov
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Lundquist, K.
    Chalmers University of Technology.
    Sipilä, J.
    University of Helsinki.
    On the distribution of the diastereomers of the structural elements in lignins: the steric course of reactions mimicking lignin biosynthesis1993Inngår i: Wood Science and Technology, ISSN 0043-7719, E-ISSN 1432-5225, Vol. 27, nr 4, s. 281-286Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Stereochemical studies on the formation of the diastereomers of arylglycerol-β-aryl ether structures during lignin biosynthesis have been carried out with model compounds. The addition of water to quinone methides of the β-syringyl ether type gives arylglycerol β-syringyl ethers with a predominance of the erythro isomer when the pH of the medium is low. Since erythro forms of arylglycerol β-syringyl ethers are prevalent in hardwood lignins, this indicates that the pH of the medium in which lignin biosynthesis occurs is lower than has been assumed until now. Equilibration studies with non-phenolic model compounds of the arylglycerolβ-guaiacyl ether and β-syringyl ether types under acidolysis conditions indicate that the erythro predominance observed in the syringyl ethers in lignins does not correspond to equilibrium conditions. A remarkable resistance to acidolysis is observed in the model compounds of etherified syringylglycerol β-syringyl ether type.

  • 133.
    Brännström, Mattias
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Integrated strength grading2009Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    This work comprises strength grading for structural timber according to European standards and prediction of grade-determining properties by various technologies and in various stages of the sawmilling process. The detection technologies applied on logs were outer shape scanning, laser scattering, x-ray scanning and resonance analysis. For boards, microwaves, laser scattering, x-ray scanning, resonance analysis and visual scanning applied. Tracing of log rotation angle has been done to enable reconstruction of boards based on the log-scanning results. Modelling of strength, modulus of elasticity and density has been done using partial least squares. A method for deriving settings for structural grades based on several modelled properties has been proposed: the smallest increment algorithm. Classification to structural grades has been made by this algorithm and by classification trees, all validated according to the method stipulated in the standard. Visual override was studied by grading strictly on deformation criteria. Profitability of a grading process has been studied, based on relative net mill prices and production costs for structural timber and alternate grades from 2007. The quality of the grades has been briefly studied by analysis of the lower tail of some strength distributions. The result shows that all grade-determining properties must be estimated to achieve high raw material utilization and quality. The means for such estimation is not important, but the quality of the variables derived, based on the technology, is critical to the result. It was shown that tracheid-effect scanning by laser scattering gave variables valuable for strength prediction and that microwave signals in a very basic form provided more information than density alone. Log scanning by x-ray and resonance analysis enabled machine strength grading to the strength grade C40 already at the timber yard. It was indicated that the log-graded material below the 5th percentile was weaker than the board-graded material of the same grade. The result from pregrading by log grading showed itself in improved profitability for certain grade combinations and market conditions. As expected, the financial result is strongly dependent on the structural timber and alternate grade properties and price, grading accuracy and properties of the species. Different equipment can classify a specimen differently, although the final properties of the final grade fulfil the requirements for both machines. For this reason, it is important to select the stronger material in pregrading. Doing the opposite will alter the distribution to the unsafe side. The conclusion is that an integrated strength-grading process gives flexibility and enables the producer to meet well-defined customer specifications for structural wood products.

  • 134.
    Brännström, Mattias
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    The impact of a strength grading process on sawmill profitability and product quality2009Inngår i: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 4, nr 4, s. 1430-1454Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A strength grading process, starting with log grading, was studied with respect to grading yield, impact on quality, and economic efficiency when visual grades according to Nordic grading rules were used for alternate product comparison. Pine (Pinus sylvestris) and spruce (Picea abies) logs and boards were graded with several varieties of commercial grading and strength-grading equipment. The boards were destructively tested, and the European grade-determining properties strength, stiffness, and density were measured. Models for these were made by partial least squares and validated. A method for the derivation of settings for multiple indicating properties, which increased yield in some cases, was proposed and evaluated. Grading to grade combinations of C40, C30, and C18 was done. The impact of visual override based on deformations was also studied. A simplified economic and sensitivity analysis was done. The outcome was that log grading can be used for strength grading with good economic and quality results. Strength pregrading on logs improves sawmill economy, depending on the species and market situation. Drying quality greatly influences the yield through visual override grading on deformations. Market prices of high grades (>C30) must improve in order to stimulate supply, as it is more economical to produce lower grades.

  • 135. Brännström, Mattias
    et al.
    Manninen, Janne
    Stora Enso AB, Porvoo.
    Oja, Johan
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Predicting the strength of sawn wood by tracheid laser scattering2008Inngår i: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 3, nr 2, s. 437-451Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    An industrial laser light scattering scanner, designed to detect the spiral grain angle of logs by the light scattering along the grain, was used on two large samples of Norway spruce (Picea abies (var. Karst)) in various sawn dimensions (approximately 750 pieces). Additional measurements were made by other techniques, such as X-ray scanning, resonance frequency measurement, and various manual measurements. The strength properties of the boards were measured by destructive testing in four-point bending according to European standard. Multivariate methods (PLS) were used to model the relationship between the bending strength of the board (MOR) and the measurements. Based only on the output from the simple tracheid scattering equipment, a model for MOR achieved an R² exceeding 0.3. Combinations with average density or outer shape parameters from log scanning resulted in R² 0.4 and 0.3 respectively, although these parameters alone only accounted for R² 0.2. The results can be used to increase the understanding of strength in wood and in an improved industrial strength-grading process.

  • 136. Brännström, Mattias
    et al.
    Manninen, Janne
    Oja, Johan
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Tracheid laser scattering: a simple tool for a rough strength estimation2006Konferansepaper (Annet vitenskapelig)
  • 137. Brännström, Mattias
    et al.
    Oja, Johan
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Grönlund, Anders
    Predicting board strength by X-ray scanning of logs: the impact of different measurement concepts2007Inngår i: Scandinavian Journal of Forest Research, ISSN 0282-7581, E-ISSN 1651-1891, Vol. 22, nr 1, s. 60-70Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The objective of this study was to compare the individual board strength predictions from an X-ray log scanner by using either two or four X-ray directions. The benefit of applying traceability between log and board was also studied. In total, 119 Norway spruce [Picea abies (L.) Karst.] sawlogs were scanned by an X-ray log scanner at the log sorting station of a sawmill and sawn into two centre pieces per log. Individual board traceability was enabled by following the rotational position of the log in the scanner and at the succeeding sawing. All boards were graded by a commercial strength grading machine before destructive testing was done. The resulting data were used to derive variables for building multivariate partial least squares strength prediction models. In the modelling a hierarchical modelling approach was used, where annual ring width, dry density and elasticity were also modelled. For all concepts studied the models' fit was similar. Only minor benefits could be found when using four directions and traceability compared with two directions and no traceability. One conclusion is that the result for traceability, from four directions in particular, is more sensitive for the interior knot reconstruction result. The strength prediction was on the same R2 level as for the strength grading machine

  • 138.
    Brännström, Mattias
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Westin, Jerker
    Dalarna University.
    Classification of structural timber by decision trees: a comparison to the certified method2009Inngår i: Forest products journal, ISSN 0015-7473, Vol. 59, nr 3, s. 53-61Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This work is all example of how to adapt a classification method, in this case a classification tree, to the present standardized method for the development of settings for strength-grading machines. Data from commercially available industrial strength-grading equipment were used oil a large sample (approximately 1,440 pieces) of Norway spruce (Picea abies (L. Karsten)) ill various sawn dimensions. The equipment used was a multisensor scanning device combining planar x-ray and resonance frequency measurement. Destructive testing was done according to European standard EN408. The pal was to make the classification, based on machine data, as close as possible to the optimum grading, which was done according to standard. Two different approaches for classification by cost-sensitive decision trees were applied to the data and compared to classification accredited according to EN14081. Classification accuracy increased from 64 percent correctly classified to 73 percent, and a reduction from 33 percent False Negative to 23 percent was achieved. False Positive increased from 3 to 4 percent. The Outcome was all increase ill value for the producer of 0.9 to 2.1 percent at 2007 average price level. The improvement came primarily from all in-yield increase in C30 of 10 percent.

  • 139.
    Buck, Dietrich
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Mechanics of Cross-Laminated Timber2018Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Increasing awareness of sustainable building materials has led to interest in enhancing the structural performance of engineered wood products. Wood is a sustainable, renewable material, and the increasing use of wood in construction contributes to its sustainability. Multi-layer wooden panels are one type of engineered wood product used in construction.

    There are various techniques to assemble multi-layer wooden panels into prefabricated, load-bearing construction elements. Assembly techniques considered in the earliest stages of this research work were laminating, nailing, stapling, screwing, stress laminating, doweling, dovetailing, and wood welding. Cross-laminated timber (CLT) was found to offer some advantages over these other techniques. It is cost-effective, not patented, offers freedom of choice regarding the visibility of surfaces, provides the possibility of using different timber quality in the same panel at different points of its thickness, and is the most well-established assembly technique currently used in the industrial market.

    Building upon that foundational work, the operational capabilities of CLT were further evaluated by creating panels with different layer orientations. The mechanical properties of CLT panels constructed with layers angled in an alternative configuration produced on a modified industrial CLT production line were evaluated. Timber lamellae were adhesively bonded in a single-step press procedure to form CLT panels. Transverse layers were laid at a 45° angle instead of the conventional 90° angle with respect to the longitudinal layers’ 0° angle.

    Tests were carried out on 40 five-layered CLT panels, each with either a ±45° or a 90° configuration. Half of these panels were evaluated under bending: out-of-plane loading was applied in the principal orientation of the panels via four-point bending. The other twenty were evaluated under compression: an in-plane uniaxial compressive loading was applied in the principal orientation of the panels. Quasi-static loading conditions were used for both in- and out-of-plane testing to determine the extent to which the load-bearing capacity of such panels could be enhanced under the current load case. Modified CLT showed higher stiffness, strength, and fifth-percentile characteristics, values that indicate the load-bearing capacity of these panels as a construction material. Failure modes under in- and out-of-plane loading for each panel type were also assessed.

    Data from out-of-plane loading were further analysed. A non-contact full-field measurement and analysis technique based on digital image correlation (DIC) was utilised for analysis at global and local scales. DIC evaluation of 100 CLT layers showed that a considerable part of the stiffness of conventional CLT is reduced by the shear resistance of its transverse layers. The presence of heterogeneous features, such as knots, has the desirable effect of reducing the propagation of shear fraction along the layers. These results call into question the current grading criteria in the CLT standard. It is suggested that the lower timber grading limit be adjusted for increased value-yield.

    The overall experimental results suggest the use of CLT panels with a ±45°-layered configuration for construction. They also motivate the use of alternatively angled layered panels for more construction design freedom, especially in areas that demand shear resistance. In addition, the design possibility that such 45°-configured CLT can carry a given load while using less material than conventional CLT suggests the potential to use such panels in a wider range of structural applications. The results of test production revealed that 45°-configured CLT can be industrially produced without using more material than is required for construction of conventional 90°-configured panels. Based on these results, CLT should be further explored as a suitable product for use in more wooden-panel construction.

  • 140.
    Buck, Dietrich
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Hagman, Olle
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Mechanics of diagonally layered cross-laminated timber2018Konferansepaper (Fagfellevurdert)
  • 141.
    Buck, Dietrich
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Hagman, Olle
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Production and In-Plane Compression Mechanics of Alternatively Angled Layered Cross-Laminated Timber2018Inngår i: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 13, nr 2, s. 4029-4045Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Increasing awareness of sustainable building materials has led to interest in enhancing the structural performance of engineered wood products. This paper reports mechanical properties of cross-laminated timber (CLT) panels constructed with layers angled in an alternative configuration on a modified industrial CLT production line. Timber lamellae were adhesively bonded together in a single-step press procedure to form CLT panels. Transverse layers were laid at an angle of 45°, instead of the conventional 90° angle with respect to the longitudinal layers’ 0° angle. Tests were carried out on 20 five-layered CLT panels divided into two matched groups with either a 45° or a 90° configuration; an in-plane uniaxial compressive loading was applied in the principal orientation of the panels. These tests showed that the 45°-configured panels had a 30% higher compression stiffness and a 15% higher compression strength than the 90° configuration. The results also revealed that the 45°-configured CLT can be industrially produced without using more material than is required for conventional CLT 90° panels. In addition, the design possibility that the 45°-configured CLT can carry a given load while using less material also suggests that it is possible to use CLT in a wider range of structural applications.

  • 142.
    Buck, Dietrich
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Hagman, Olle
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Wang, Alice
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Gustafsson, Anders
    SP Technical Research Institute of Sweden, SP Sustainable Built Environment, Skellefteå.
    Further Development of Cross-Laminated Timber (CLT): Mechanical Tests on 45° Alternating Layers2016Inngår i: WCTE 2016 : Proceedings, Vienna: Vienna University of Technology, Austria , 2016Konferansepaper (Fagfellevurdert)
    Abstract [en]

     

    In this paper, a series of experimental bending and compression tests were performed on cross-laminated timber (CLT) products with ±45° alternating layers, to evaluate their performance against conventional panels of 90° orientation. Engineered wood products, such as CLT with ±45° alternating layers can provide opportunities for greater use in larger and more sustainable timber constructions. A total of 40 panels, manufactured in an industrial CLT production line with either of these two configurations, were tested and compared. Panels were evaluated in bending tests n=20 and the remaining ones in compression tests. Results showed that 35% increased the strength in the four-point bending tests for panels containing ±45° alternating layers compared with the 90° alternating layers. Compression strength was increased by 15%. Stiffness increased by 15% in the four-point bending and 30% in the compression. The results indicate that CLT containing ±45° alternating layers has increased strength and stiffness compared to 90° alternating layers. These findings suggest that further developments in CLT are feasible in advanced building applications.

  • 143.
    Buck, Dietrich
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Wang, Alice
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Hagman, Olle
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Gustafsson, Anders
    SP Technical Research Institute of Sweden, SP Sustainable Built Environment, Skellefteå, Sweden, SP Trätek, SP Technical Research Institute of Sweden, Skellefteå.
    Bending Properties of Cross Laminated Timber (CLT) with a 45° Alternating Layer Configuration2016Inngår i: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 11, nr 2, s. 4633-4644Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Bending tests were conducted with cross laminated timber (CLT) panels made using an alternating layer arrangement. Boards of Norway spruce were used to manufacture five-layer panels on an industrial CLT production line. In total, 20 samples were tested, consisting of two CLT configurations with 10 samples of each type: transverse layers at 45° and the conventional 90° arrangement. Sample dimensions were 95 mm × 590 mm × 2000 mm. The CLT panels were tested by four point bending in the main load-carrying direction in a flatwise panel layup. The results indicated that bending strength increased by 35% for elements assembled with 45° layers in comparison with 90° layers. Improved mechanical load bearing panel properties could lead to a larger span length with less material.

  • 144.
    Buck, Dietrich
    et al.
    Department of Engineering Sciences and Mathematics, Luleå University of Technology.
    Wang, Xiaodong (Alice)
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Hagman, Olle
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Gustafsson, Anders
    SP Technical Research Institute of Sweden, SP Sustainable Built Environment, Skellefteå, Sweden.
    Comparison of Different Assembling Techniques Regarding Cost, Durability, and Ecology: A Survey of Multi-layer Wooden Panel Assembly Load-Bearing Construction Elements2015Inngår i: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 10, nr 4, s. 8378-8396Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Wood is a pure, sustainable, renewable material. The increasing use of wood for construction can improve its sustainability. There are various techniques to assemble multi-layer wooden panels into prefabricated, load-bearing construction elements. However, comparative market and economy studies are still scarce. In this study, the following assembling techniques were compared: laminating, nailing, stapling, screwing, stress laminating, doweling, dovetailing, and wood welding. The production costs, durability, and ecological considerations were presented. This study was based on reviews of published works and information gathered from 27 leading wood product manufacturing companies in six European countries. The study shows that the various techniques of assembling multi-layer wooden construction panel elements are very different. Cross laminated timber (CLT) exhibited the best results in terms of cost and durability. With regard to ecological concerns, dovetailing is the best. Taking into account both durability and ecological considerations, wooden screw-doweling is the best. These alternatives give manufacturers some freedom of choice regarding the visibility of surfaces and the efficient use of lower-quality timber. CLT is the most cost-effective, is not patented, and is a well-established option on the market today.

  • 145.
    Busatto, Tatiano
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik. Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    On the Interaction Between Efficient Light Bulbs and Photovoltaic Systems in Low-Voltage Networks2018Rapport (Annet (populærvitenskap, debatt, mm))
    Abstract [en]

    Thanks to the continuous technological development, from time-to-time, new devices emerge in the market to improve our daily life in several ways. Two of these technologies are addressed in this work, in the power quality context on consumption and generation, and in their integration with the electric power system.

    The first refers to the energy efficient lamps, which are massively represented by the LED lamps, found in almost every household, industry or commercial installation.The second is about photovoltaic (PV) power generation, which is less in numbers compared to the first, but still presents a continuous growing in popularity and already a substantial amount in terms of installed capacity. Both technologies have benefits to the environment. LED lamps are more efficient compared to earlier technologies, helping to reduce the global power consumption. PV generation allows producing electricity from an environment friendly source.

    Research and development result in continuous improvements in both technologies. Also, phenomena related to compatibility with grid and performance for individual devices are reasonably well understood.However, there is no such general understanding on the electrical interactions between these two devices (i.e between LED lamps and PV inverters). For instance, it is still not clear how the control from both LED lamps and PV inverters are affected under parallel operation, or how the performance and lifetime changes due the mutual impact the devices have on each other.

    This half-way report addresses a number of issue related to the electrical interactions between PV generation and LED lamps in low-voltage networks; specifically with respect to harmonics and supraharmonics.

    Power quality analysis has been performed in the time and frequency-domain covering different frequencies ranges. Investigation methodology includes the use of simulation and measurements in realistic scenarios, in a controllable laboratory environment. For this, a set of LED lamps and PV Inverters currently found in the market are used to characterize the operation of the devices in terms of current emission and equivalent impedance.

    For the LED lamps, primary current emission is evaluated and correlated with the different circuit topologies. The impedance characterization is performed by invasive measurement methods described in the literature, in combination with a proposed method for estimation of the internal capacitances. For the latter, a non-invasive capacitance measurement is presented, followed by experimental measurements. Some of the results show that the equivalent input capacitances of LED lamps are a few tens of nF. Furthermore, from the circuit analysis, some of the most common topologies in terms of EMI filters topologies, and AC/DC converters are revealed.

    Regarding PV inverters, simulations for different topologies and modulation strategies are performed under external influence from the source supply. Characterization of the grid variations and its impact on inverters is performed through quantification of harmonics and supraharmonics.Some of the results have revealed the low-order harmonics sensitivity when the source supply is not purely sinusoidal, besides dependence of the supraharmonic emissions on the inverter topology. Additionally, the study includes a set of PV inverters impedance measurements in order to understand the common association with the rest of the system.

    As a third part, the influence of the low-voltage network impedance is examined. From simulation of real networks, the network impedance is analyzed and of the results are discussed with respect to resonances for harmonic propagation and stability of power converters. A method was developed to determine the harmonic impedances in low-voltage networks in a stochastic way by using Monte Carlo simulation with the customer impedance as the random variable. The method is applied to two existing low-voltage networks in Sweden. Results show the variation of resonant frequencies as a function of the PV penetration, besides the uncertainties in network impedance for the individual customer connections.

    Finally, preliminary results from a study case to investigate the interaction between PV inverters and LED lamps is presented. Emission and propagation of power quality disturbances for different equipment combinations and operating conditions are analyzed and results discussed. Results have revealed the harmonic interdependency and its consequences for the total harmonic distortion, next to interactions in the supraharmonic range. This work presents several findings and a comprehensive discussion serving as a guideline for future work on interaction analysis and its consequences for devices in the low-voltage network.

  • 146.
    Busatto, Tatiano
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik. Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Ravindran, Vineetha
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Larsson, Anders
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Rönnberg, Sarah
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Bollen, Math
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Measurements on an experimental laboratory setup with PV Inverters and a Large Number of LED Lamps2018Rapport (Annet (populærvitenskap, debatt, mm))
  • 147.
    Busatto, Tatiano
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Ravindran, Vineetha
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Larsson, Anders
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Rönnberg, Sarah
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Bollen, Math
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Jan, Meyer
    Technische Universität Dresden, Dresden, Germany.
    Deviations between the commonly-used model and measurements of harmonic distortion in low-voltage installations2020Inngår i: Electric power systems research, ISSN 0378-7796, E-ISSN 1873-2046, Electric Power Systems Research, ISSN 0378-7796, Vol. 180, nr 1, s. 1-6, artikkel-id 106166Artikkel i tidsskrift (Annet (populærvitenskap, debatt, mm))
    Abstract [en]

    Harmonic analysis studies of modern power systems commonly employ Norton and Thévenin equivalents at harmonic frequencies for the nonlinear devices. This approach neglects the so-called nonlinear interaction phenomenon. This paper addresses the difference between the results from the commonly-used model and the actual harmonic distortion measured in a low-voltage installation. A number of indices are introduced to quantify the nonlinear interaction. These indices allow a quantification of the extent to which the commonly-used model is also to predict harmonic voltages and currents in a modern low-voltage installation. The proposed model and the subsequent mathematical analysis are illustrated through measurements from different combinations of PV inverters and LED lamps using different technologies. The results show that deviation is dependent on the used technology, network impedance, and source voltage waveform. Other findings are that nonlinear interaction happens mainly in the low harmonic orders and impacts are more perceived on the harmonics phase angle. Possible explanations for these observations are discussed.

  • 148.
    Busatto, Tatiano
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik. Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Ravindran, Vineetha
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Rönnberg, Sarah
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Larsson, Anders
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Bollen, Math
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Jan, Meyer
    Technische Universität Dresden.
    Experimental Harmonic Analysis of the Impact of LED Lamps on PV Inverters Performance2019Inngår i: 11th Internation Conference on Electric Power Quality and Supply Reliability, Estonia, June 12-15, 2019., 2019Konferansepaper (Fagfellevurdert)
    Abstract [en]

    It is known for instance that voltage waveform distortion and network impedance have a significant impact on PV inverter current emissions. Because this, much research is still required to better understand their behavior and impact when multiple common household devices are placed to operate together in the same low-voltage installation. In particular, this paper addresses the harmonic impact of LED lamps on PV inverters performance considering different technologies and number of lamps. The analysis has been carried out with different scenarios considering two types of LED lamps, with and without power factor correction feature, and three different PV inverter technologies. The evaluation of the impacts is simply performed by frequency and time domain analysis, establishing the correlation between the devices current harmonics. The results obtained from the experiments have shown that LED lamps are prone to add a significant impact on the PV inverter current harmonics, and this impact is mainly dependent on the devices used technology

  • 149.
    Bystedt, Anders
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    A wood construction network and the view on subcontractor systems: A Swedish experience2007Inngår i: The Future of Nordic Business Schools: 19th Nordic Academy of Management Conference, 2007Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The Swedish construction market is characterised in a too low endurable housing production at a too high cost level. Forces are raised to increase the production and lowering the production costs without repeating the experienced mistakes from the Million programs of the 1970s. Thus, the construction market in Sweden faces a challenge in building more apartments at a lower price in buildings that are flexible in design and fit into surroundings. The wood manufacturing industry has found that there is a possibility to meet the demands of the market. In the report More Wood in Construction – Foundation for a National Strategy (DS 2004:1 transl.)* there has been found that there is a potential in wood construction of multi storey buildings. The research in wood construction has mainly been done in the field of technology. In the report there is an interest in new business concepts; one of these concepts is strategic networks. A strategic network can bee seen as a tool for excellence, where different competence in the network create the knowledge needed to be an interesting partner in the constructing area. But the production in the This paper examines the questions of what demands a strategic network state on sub contractors in an industrialised wood construction process and how the integration should be managed. The questions deals with the view on cooperation in the surrounding of the strategic network; this cooperation is needed in areas where the network itself does not have the knowledge needed. A case study in an ongoing creation process of a strategic network will be presented. The project has been studied through interviews with leading representatives at different actors involved in the strategic network creation process. The empirical results show that there is not a neglectable degree of cooperation needed between the network and the sub contractor system. The cooperation involves development in the construction system and a close connection to the different businesses in the strategic network. One tentative suggestion is that the strategic network view is that the sub contractor has to be able to add value to the construction system and take part in developing it; I simply regard the sub contractor being a semimember rather than a contractor. This view creates a new situation and a new way of acting both for the sub contractor and the business in the construction area. *Mer trä i byggandet – Underlag för en nationell strategi (DS 2004:1)

  • 150.
    Bystedt, Anders
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Conditions for industrialised wood construction: A Swedish experience2005Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The Swedish construction market is today characterised in a too low endurable housing production at a too high cost level. Forces are raised to increase the production and lowering the production costs without repeating the mistakes from the Million programs of the 1970s. The construction market in Sweden faces a challenge in building more at a lower price in buildings that is flexible in design and fits into the surroundings. This paper examines the factors and instruments that are conclusive for the wood industry to create an industrialised wood constructing actor. A case conducted in an ongoing wood building project in the middle part of Sweden will be presented. The project has been studied through interviews with representatives, in high positions, at the different actors involved in the project. The empirical results show that there are not an unessential degree of factors affecting the creation of an industrialised wood construction actor. The most important factors lie in the area for project organisation, cooperation forms, common terminology and control over resources and activities. One tentative suggestion is that the industrial network should be seen as an instrument for the development and the success in creating an efficient industrialised wood constructing actor.

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