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  • 151. Chacha, N.
    et al.
    Toven, K
    RISE, Innventia, PFI – Paper and Fiber Research Institute.
    Mtui, G
    Katima, J
    Mrema, G
    Steam Pretreatment of Pine (Pinus patula) wood residue for the production of reducing sugars2011Inngår i: Cellulose Chemistry and Technology, ISSN 0576-9787, Vol. 45, s. 495-501Artikkel i tidsskrift (Fagfellevurdert)
  • 152. Chang, Shan-Shan
    et al.
    Salmen, Lennart
    RISE., Innventia.
    Olsson, Anne-Mari
    RISE., Innventia.
    Clair, Bruno
    Deposition and organisation of cell wall polymers during maturation of poplar tension wood by FTIR microspectroscopy2014Inngår i: Planta, ISSN 0032-0935, E-ISSN 1432-2048, Vol. 239, nr 1, s. 243-254Artikkel i tidsskrift (Fagfellevurdert)
  • 153. Chang, S.-S.
    et al.
    Salmen, L.
    RISE, Innventia.
    Olsson, A.-M.
    RISE, Innventia.
    Clair, B.
    Deposition and organisation of cell wall polymers during maturation of poplar tension wood by FTIR microspectroscopy2014Inngår i: Planta, ISSN 0032-0935, E-ISSN 1432-2048, Vol. 239, nr 1, s. 243-254Artikkel i tidsskrift (Fagfellevurdert)
  • 154. Chen, Z. -Q
    et al.
    Abramowicz, K.
    Raczkowski, R.
    Ganea, S.
    Wu, H. X.
    Lundqvist, Sven-Olof
    RISE, Innventia.
    Mörling, T.
    De Luna, S. S.
    Garci­a Gil, M. R.
    Mellerowicz, E. J.
    Method for accurate fiber length determination from increment cores for large-scale population analyses in Norway spruce2016Inngår i: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 70, nr 9, s. 829-838Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Fiber (tracheid) length is an important trait targeted for genetic and silvicultural improvement. Such studies require large-scale non-destructive sampling, and accurate length determination. The standard procedure for non-destructive sampling is to collect increment cores, singularize their cells by maceration, measure them with optical analyzer and apply various corrections to suppress influence of non-fiber particles and cut fibers, as fibers are cut by the corer. The recently developed expectation-maximization method (EM) not only addresses the problem of non-fibers and cut fibers, but also corrects for the sampling bias. Here, the performance of the EM method has been evaluated by comparing it with length-weighing and squared length-weighing, both implemented in fiber analyzers, and with microscopy data for intact fibers, corrected for sampling bias, as the reference. This was done for 12-mm increment cores from 16 Norway spruce (Picea abies (L.) Karst) trees on fibers from rings 8-11 (counted from pith), representing juvenile wood of interest in breeding programs. The EM-estimates provided mean-fiber-lengths with bias of only +2.7% and low scatter. Length-weighing and length2-weighing gave biases of-7.3% and +9.3%, respectively, and larger scatter. The suggested EM approach constitutes a more accurate non-destructive method for fiber length (FL) determination, expected to be applicable also to other conifers.

  • 155. Chen, Z. -Q
    et al.
    Karlsson, B.
    Lundqvist, Sven-Olof
    RISE, Innventia.
    Garci­a Gil, M. R.
    Olsson, Lars
    RISE, Innventia.
    Wu, H. X.
    Estimating solid wood properties using Pilodyn and acoustic velocity on standing trees of Norway spruce2015Inngår i: Annals of Forest Science, Vol. 72, nr 4, s. 499-508Artikkel i tidsskrift (Fagfellevurdert)
  • 156. Chen, Zhi-Qiang
    et al.
    Abramowicz, Konrad
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för matematik och matematisk statistik.
    Raczkowski, Rafal
    Ganea, Stefana
    Wu, Harry X.
    Lundqvist, Sven-Olof
    Mörling, Tommy
    Sjöstedt de Luna, Sara
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för matematik och matematisk statistik.
    Gil, Maria Rosario Garcia
    Mellerowicz, Ewa J.
    Method for accurate fiber length determination from increment cores for large-scale population analyses in Norway spruce2016Inngår i: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 70, nr 9, s. 829-838Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Fiber (tracheid) length is an important trait targeted for genetic and silvicultural improvement. Such studies require large-scale non-destructive sampling, and accurate length determination. The standard procedure for non-destructive sampling is to collect increment cores, singularize their cells by maceration, measure them with optical analyzer and apply various corrections to suppress influence of non-fiber particles and cut fibers, as fibers are cut by the corer. The recently developed expectation-maximization method (EM) not only addresses the problem of non-fibers and cut fibers, but also corrects for the sampling bias. Here, the performance of the EM method has been evaluated by comparing it with length-weighing and squared length-weighing, both implemented in fiber analyzers, and with microscopy data for intact fibers, corrected for sampling bias, as the reference. This was done for 12-mm increment cores from 16 Norway spruce (Picea abies (L.) Karst) trees on fibers from rings 8-11 (counted from pith), representing juvenile wood of interest in breeding programs. The EM-estimates provided mean-fiber-lengths with bias of only +2.7% and low scatter. Length-weighing and length2-weighing gave biases of -7.3% and +9.3%, respectively, and larger scatter. The suggested EM approach constitutes a more accurate non-destructive method for fiber length (FL) determination, expected to be applicable also to other conifers.

  • 157. Chen, Z.-Q.
    et al.
    Gil, M.R.G.
    Karlsson, B.
    Lundqvist, S.-O.
    RISE, Innventia.
    Olsson, L.
    RISE, Innventia.
    Wu, H.X.
    Inheritance of growth and solid wood quality traits in a large Norway spruce population tested at two locations in southern Sweden: Relation to barrier and mechanical properties2014Inngår i: Tree Genetics & Genomes, ISSN 1614-2942, E-ISSN 1614-2950, nr 5, s. 1291-1303Artikkel i tidsskrift (Fagfellevurdert)
  • 158. Chen, Z.-Q.
    et al.
    Karlsson, B.
    Mörling, T
    Olsson, Lars
    RISE, Innventia.
    Mellerowicz, E.J
    Wu, H.X.
    Lundqvist, Sven-Olof
    RISE, Innventia.
    Gil, M.R.G.
    Genetic analysis of fiber dimensions and their correlation with stem diameter and solid-wood properties in Norway spruce2016Inngår i: Tree Genetics & Genomes, ISSN 1614-2942, E-ISSN 1614-2950, Vol. 12, nr 6Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Adverse genetic correlations between growth traits and solid-wood, as well as fiber traits are a concern in conifer breeding programs. To evaluate the impact of selection for growth and solid-wood properties on fiber dimensions, we investigated the inheritance and efficiency of early selection for different wood-fiber traits and their correlations with stem diameter, wood density, modulus of elasticity (MOE), and microfibril angle (MFA) in Norway spruce (Picea abies L). The study was based on two large open-pollinated progeny trials established in southern Sweden in 1990 with material from 524 families comprising 5618 trees. Two increment cores were sampled from each tree. Radial variations from pith to bark were determined for rings 3–15 with SilviScan for fiber widths in the radial (RFW) and tangential (TFW) direction, fiber wall thickness (FWT), and fiber coarseness (FC). Fiber length (FL) was determined for rings 8–11. Heritabilities based on rings 8–11 using joint-site data were moderate to high (0.24–0.51) for all fiber-dimension traits. Heritabilities based on stem cross-sectional averages varied from 0.34 to 0.48 and reached a plateau at rings 6–9. The “age-age” genetic correlations for RFW, TFW, FWT, and FC cross-sectional averages at a particular age with cross-sectional averages at ring 15 reached 0.9 at rings 4–7. Our results indicated a moderate to high positive genetic correlation for density and MOE with FC and FWT, moderate and negative with RFW, and low with TFW and FL. Comparison of several selection scenarios indicated that the highest profitability is reached when diameter and MOE are considered jointly, in which case, the effect on any fiber dimension is negligible. Early selection was highly efficient from ring 5 for RFW and from rings 8–10 for TFW, FWT, and FC.

  • 159.
    Cool, Julie
    et al.
    University of British Columbia.
    Fredriksson, Magnus
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Avramidis, Stavros
    University of British Columbia.
    Automatic knot detection in coarse resolution cone-beam CT images of softwood logs2017Inngår i: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434XArtikkel i tidsskrift (Fagfellevurdert)
  • 160.
    Cool, Julie
    et al.
    University of British Columbia.
    Fredriksson, Magnus
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Avramidis, Stavros
    University of British Columbia.
    Knot detection in coarse resolution CT images of logs2017Inngår i: International Wood Machining Seminar (IWMS-23), 2017Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The use of X-ray computed tomography (CT) scanning of logs in sawmill is becoming a reality in the last few years, usually with rather costly and complex machines resembling medical scanners. However, a scanning solution has been developed that is less costly and more robust, and therefore more suited for sawmill needs. The rather coarse data from this machine has not been fully evaluated regarding possibilities to detect internal features such as knots. In this study, a knot detection algorithm developed for medical scanners was applied to images from a coarse resolution scanner, from four different logs of various species, and with different image resolution. The objective was to see if it was possible to detect knots automatically in the images. If so, the aim was to calculate the knot detection rate and the accuracy of detected knot size and position. These numbers were calculated compared to manually measured reference knots. This resulted in a knot detection rate of about 53 % overall, and a well detected knot position, but poorly detected knot size. It is possible to observe a certain difference between species and reconstruction resolution, however the material is too small to draw any definite conclusions. As a preliminary study, it provides input for further investigation on knot detection in coarse resolution X-ray CT images. Future work involves scanning more logs to get more data, and to pinpoint the resolution needed for accurate knot detection using the current algorithm.

  • 161.
    Cool, Julie
    et al.
    University of British Columbia.
    Fredriksson, Magnus
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Stephen, James D
    Queen’s University.
    Mabee, Warren E
    Queen’s University.
    Avramidis, Stavros
    University of British Columbia.
    Bull, Gary Q
    University of British Columbia.
    An Integrated Forest Products Cluster for Off-Grid Lumber Production Using Biomass CHP in Remote Indigenous Communities2017Konferansepaper (Fagfellevurdert)
  • 162.
    Couceiro, José
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Hansson, Lars
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Sandberg, Dick
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Ahec, Ambroz
    University of Ljubljana.
    CT-scanning of the drying process of Eucalyptus nitens.2018Inngår i: Proceedings of IDS 2018 21st International Drying Symposium. / [ed] Cárcel JA, Polo GC, García-Pérez JV, Mulet A, Rosselló C.,, Valencia: Editorial Universitat Politècnica de València , 2018, s. 1269-1276Konferansepaper (Fagfellevurdert)
  • 163.
    Couceiro, José
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Lindgren, Owe
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Estimation of miosture content in wood using dual x-ray energies in a medical CT-scanner2016Inngår i: Process Technologies for the Forest & Biobased Products Industries: PTF BPI 2016, 2016, s. 22-Konferansepaper (Annet vitenskapelig)
  • 164.
    Couceiro, José
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Neyses, Benedikt
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Sandberg, Dick
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    In-situ moisture content and density measurements in surface densified wood using dual X-ray absorptiometry in medical CT-scanning2016Inngår i: BIOCOMP 2016: The 13th Pacific Rim Bio-Based Composites Symposium, Bio-based composites for a sustainable future., Concepción: University of Concepción , 2016, Vol. 2, s. 92-, artikkel-id NA01Konferansepaper (Fagfellevurdert)
  • 165.
    Couceiro, José
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    Sandberg, Dick
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknologi.
    The use of X-ray computed tomography in bio-composite research2016Inngår i: BIOCOMP 2016: The 13th Pacific Rim Bio-Based Composites Symposium : Bio-based composites for a sustainable future,, Conceptión: University of Concepción , 2016, s. 42-45Konferansepaper (Fagfellevurdert)
    Abstract [en]

    X-ray computed tomography (CT), which was introduced in the medical field in the early 1970s, is also a powerful tool for the non-destructive measurement of dynamic processes in wood. For more than 20 years, medical CT has been used in wood research at Luleå University of Technology. The uniqueness of the CT equipment allowsprocesses such as drying, modification; water absorption; internal and external cracking; and material deformation to be studied in temperature- and humidity-controlled environments. The data recorded by the CT scanner during the process is converted into two or three dimensional images that, for instance, can show dynamic moisture behaviour in wood drying and crack formation. This paper provides an overview of the possibilities of using CT in bio-composite research, and shows examples of applications and results that can be particularly difficult to achieve using other methods. A specific focus is on studies on wood products that use combinations with materials such as metal and especially about how to deal with the difficulties that this entails.The practical application of the result is that CT scanning, combined with image processing, can be used for non-destructive and non-contact three-dimensional s tudies of exterior construction elements during water sorption and desorption, to study parameters such as swelling and shrinking behaviour; delamination phenomena; and crack development.

  • 166.
    Couceiro, José
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Sehlstedt-Persson, Margot
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Hansson, Lars
    Norwegian University of Science and Technology (NTNU), Department of ICT and Natural Sciences, Norway.
    Hagman, Olle
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Sandberg, Dick
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    CT scanning of capillary phenomena in bio-based materials2017Inngår i: Pro Ligno, ISSN 1841-4737, E-ISSN 2069-7430, Vol. 13, nr 4, s. 181-187Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    X-ray computed tomography (CT) is a powerful tool for the non-destructive study of dynamic moisture processes in wood and other bio-based materials. In the CT facilities at Luleå University of Technology, it is possible to study wood-moisture relations such as water absorption, drying and related material deformation under a temperature- and humidity-controlled environment.An increase in the use of bio-based materials in building construction has led to an increased interest in capillary phenomena in these materials, because of an increasing number of moisture-related damage in timber and hybrid-timber buildings. This article shows some examples of how different bio-materials used in construction interact with liquid water over time. The overall purpose has been to develop the CT technique as a powerful tool for the determination and visualization of capillary flow that can be a base for modelling and an increased understanding of moisture flow in new bio-based building materials.Early-stage observation of the behaviour of different traditional and new bio-based building materials shows that CT scanning, combined with image processing, has a high potential to be used in performing non-destructive and non-contact tests that can help to increase the knowledge of water-material interactions and develop building materials with an optimized performance.

  • 167.
    Cristescu, Carmen
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Sandberg, Dick
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Karlsson, Olov
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Markers of quality in self-bonded beech boards2017Konferansepaper (Fagfellevurdert)
    Abstract [en]

    A self-bonding phenomenon takes place when five layers of beech (Fagus SylvaticaL.) veneers are pressed at temperatures higher than 200ºC. If the pressing temperature between veneer surfaces reaches at least 225ºC during pressing and if the pressure applied is optimal, water-resistant bonds are formed between veneers. This study investigates the relation of thickness reduction (marker of compression) and mass loss (marker of heat treatment intensity) to boards quality. The effect of water and water vapour on the bondings between veneer in boards pressed at 200, 225 and 250ºC is studied. The conclusion is that pressing 5 layers of 2 mm rotary-cut beech veneer parallel-fibered at 225ºC, 5 MPa and 300 s leads to a thickness reduction of 33.4 % and mass loss of 1.23 %; in such boards bondings are not resistant to liquid water but are resistant to vapour after one adsorption-desorption cycle. When pressing at 250ºC, 5 MPa and 300 seconds, the thickness reduction is 50% and the mass loss 4%; in such boards no delamination was observed when soaked in water. Boards pressed athigher temperature show lower hygroscopicity. Their equilibrium moisture content (EMC) rangedbetween 3.6 and 7%. Based on the results of this study it ishypothesised that the decay resistance of self-bonded boards will increase when increasing the severity of the hot-pressing.

  • 168.
    Cristina, Simón
    et al.
    Technical University of Madrid, Spain.
    Francisco, García Fernández
    Technical University of Madrid, Spain.
    Luis, García Esteban
    Technical University of Madrid, Spain.
    Paloma, de Palacios
    Technical University of Madrid, Spain.
    Hosseinpourpia, Reza
    University of Göttingen, Germany.
    Carsten, Mai
    University of Göttingen, Germany.
    Comparison of the saturated salt and dynamic vapor sorption methods in obtaining the sorption properties of Pinus pinea L.2017Inngår i: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 75, nr 6, s. 919-926Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Several methods are available for obtaining the sorption isotherms of wood. Among these, the saturated salt and dynamic vapor sorption methods are the most frequently used  ones. For the first time, the hygroscopic response of wood obtained using these two methods is compared. This is done by determining the 35 and 50°C adsorption isotherms of juvenile and mature wood of Pinus pinea L. The hygroscopic behavior of the two types of wood is different, as the mature wood has a higher moisture content than the juvenile wood in the isotherms studied. Comparison of the static saturated salt method and dynamic vapor sorption shows few significant differences between the equilibrium moisture content obtained by each method during the adsorption process, both in a point by point comparison and in the comparison of quadratic polynomial forms of the Guggenheim Anderson-de Boer model. Moreover, in both methods the point of relative humidity from which multilayer sorption predominates over monolayer sorption is similar.

  • 169.
    Dahlblom, O.
    et al.
    Lund University.
    Ormarsson, Sigurdur
    Lund University.
    Petersson, H.
    Lund University.
    Simulation of wood deformation processes in drying and other types of environmental loading1996Inngår i: Annales des Sciences Forestieres, ISSN 0003-4312, E-ISSN 1878-6545, Vol. 53, nr 4, s. 857-866Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Deformation processes in wood exposed to drying and other types of environmental loading are simulated by use of the finite element method. In the material model applied, the orthotropic structure of the wood material is considered. The differences of properties in the longitudinal, radial and tangential directions for stiffness parameters as well as for moisture shrinkage parameters are taken into account. As an illustration of possible application areas, the deformation development of boards during drying is simulated. In the analyses, the influence of spiral grain and the variation of wood properties with the distance from the pith are considered. The simulation yields information about unfavourable deformations that develop during the drying process., Le processus de déformation du bois exposé au séchage et autres types de charges environnementales est simulé par la méthode des éléments finis. La structure orthotropique du bois est prise en considération sur le modèle de matériel utilisé. Les différences existant au niveau des propriétés des directions longitudinales, radiales et tangentielles sont prises en compte pour les paramètres de rigidité et de contraction par humidité. Une des possibilités du champ d'applications est illustrée par le fait que l'évolution de la déformation des planches pendant le séchage est simulée. À l'échelon des analyses, l'influence du grain spiral et la variation des propriétés du bois avec la distance depuis la moelle sont pris en compte. La simulation permet d'obtenir des informations concernant l'évolution des déformations défavorables pendant le processus de séchage.

  • 170. Dahlblom, Ola
    et al.
    Lindemann, Jonas
    Ormarsson, Sigurdur
    Software for Numerical Simulation of Drying Induced Deformation of Wooden Products2003Inngår i: 8th International IUFRO Wood Drying Conference, TRANSILVANIA University of Brasov, Faculty of Wood Industry , 2003, s. 45-50Konferansepaper (Fagfellevurdert)
    Abstract [en]

    A previously developed computational model for 3D finite element simulations of wood during moisture changes is in the present work provided with a special-purpose graphical user interface. The software is designed to use a personal computer for the graphical user interface and to have possibility to use distributed computational resources for the simulation.

  • 171. Dahlblom, Ola
    et al.
    Ormarsson, Sigurdur
    Petersson, Hans
    Prediction of deformations by an extended two-dimensional formulation1996Inngår i: Quality wood drying through process modelling and novel technologies / [ed] Alain Cloutier, Yves Fortin, 1996, s. 69-76Konferansepaper (Fagfellevurdert)
  • 172.
    Dahlblom, Ola
    et al.
    Lund Institute of Technology, Sweden.
    Persson, Kent
    Lund Institute of Technology, Sweden.
    Ormarsson, Sigurdur
    Petersson, Hans
    Växjö universitet, Fakulteten för matematik/naturvetenskap/teknik, Institutionen för teknik och design.
    Stiffness and shape stability analysis of sawn timber based on experimentally found variations of wood properties1999Inngår i: Connection between Silviculture and Wood Quality through Modelling Approaches and Simulation Softwares, 1999Konferansepaper (Fagfellevurdert)
  • 173.
    Dahlblom, Ola
    et al.
    Lund Institute of Technology, Sweden.
    Persson, Kent
    Lund Institute of Technology, Sweden.
    Petersson, Hans
    Växjö universitet, Fakulteten för matematik/naturvetenskap/teknik, Institutionen för teknik och design.
    Ormarsson, Sigurdur
    Investigation of variation of engineering properties of spruce1999Inngår i: Wood Drying Research & Technology for Sustainable Forestry Beyond 2000, 1999Konferansepaper (Fagfellevurdert)
  • 174.
    Dahlblom, Ola
    et al.
    Lund Institute of Technology.
    Petersson, Hans
    Växjö universitet, Fakulteten för matematik/naturvetenskap/teknik, Institutionen för teknik och design.
    Ormarsson, Sigurdur
    Full 3-D FEM-Simulations of Drying Distortion in Spruce Boards based on Experimental Studies2001Inngår i: 7th International IUFRO Wood Drying Conference, 2001Konferansepaper (Fagfellevurdert)
  • 175.
    Dahlblom, Ola
    et al.
    Lund University, Sweden.
    Petersson, Hans
    Chalmers University of Technology, Sweden.
    Ormarsson, Sigurdur
    Chalmers University of Technology, Sweden.
    Stiffness, strength and shape stability grading analysis of sawn timber based on experimentally found growth characteristics2000Inngår i: World Conference on Timber Engineering, 2000Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Stiffness, strength and shape stability analysis of sawn timber should be based on how the material properties vary in the stem due to different growth conditions. As part of an EU study, results from investigations of the modulus of elasticity, shrinkage coefficient and spiral grain angle of spruce are presented. The variation in properties with the position in the stem has been investigated. The specimens were sawn from 274 stems in 29 stands in five countries of the European Union. A total of about 7000 small specimens were tested. Results from the modelling of stiffness and moisture-induced deformations of battens are presented. The simulations were based on material data obtained from measurements performed on specimens sawn from the same logs as the battens. The simulation results are compared with experimental results and are of interest for the development of new grading procedures for sawn timber.

  • 176. Dahlblom, Ola
    et al.
    Petersson, Hans
    Persson, Kent
    Ormarsson, Sigurdur
    Experimental investigation of basic properties of spruce1998Inngår i: World Conference on Timber Engineering, 1998Konferansepaper (Fagfellevurdert)
  • 177. Dammström, S.
    et al.
    Salmen, Lennart
    RISE., STFI-Packforsk.
    Gatenholm, P.
    On the interactions between cellulose and xylan, a biomimetic simulation of the hardwood cell wall2009Inngår i: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 4, nr 1, s. 3-14Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The plant cell wall exhibits a hierarchical structure, in which the organization of the constituents on different levels strongly affects the mechanical properties and the performance of the material. In this work, the interactions between cellulose and xylan in a model system consisting of a bacterial cellulose/glucuronoxylan (extracted from aspen, Populus tremula) have been studied and compared to that of a delignified aspen fiber material. The properties of the materials were analyzed using Dynamical Mechanical Analysis (DMA) with moisture scans together with dynamic Infra Red -spectroscopy at dry and humid conditions. The results showed that strong interactions existed between the cellulose and the xylan in the aspen holocellulose. The same kinds of interactions were seen in a water-extracted bacterial cellulose/xylan composite, while unextracted material showed the presence of xylan not interacting with the cellulose. Based on these findings for the model system, it was suggested that there is in hardwood one fraction of xylan that is strongly associated with the cellulose, taking a similar role as glucomannan in softwood.

  • 178.
    Danesh, Mohammad Amin
    et al.
    Islamic Azad University, Iran.
    Ziaei Tabari, Hassan
    Islamic Azad University, Iran.
    Hosseinpourpia, Reza
    Georg-August University, Germany.
    Nazarnezhad, Noradin
    Sari Agricultural Science and Natural Resources University, Iran.
    Shams, Morteza
    Islamic Azad University, Iran.
    Investigation of the morphological and thermal properties of waste newsprint/recycled polypropylene/nanoclay composite2012Inngår i: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 7, nr 1, s. 936-945Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The main objective of this research was to study the potential of waste polypropylene and waste newsprint fiber for making wood-plastic nanocomposites. We used 30 wt.% waste newsprint fiber and 10 wt.% compatilizer in this study. Nanoclay was used at two levels: 2.5 and 5% by wt. Materials were mixed with either recycled or virgin polypropylene. The effects of nanoclay (NC) on the mechanical and thermal properties were also studied. The improvements in tensile properties of the blended composites with the addition of NC were further supported by Scanning Electron Microscope (SEM) micrographs and X-Ray Diffraction (XRD) data. Thermal degradation behavior of the composites showed that the degradation temperatures shifted to higher values after addition of nanoclay. The XRD data showed that the relative intercalation of composites with 2.5% nanoclay was higher than 5% nanoclay. The experimental results demonstrated that the waste materials could be used as appropriate alternative raw materials for making low cost wood-plastic composites (WPCs).

  • 179.
    de Borst, Karin
    et al.
    University of Glasgow, UK.
    Bader, Thomas K.
    Vienna University of Technology, Austria.
    Structure-€“function relationships in hardwood: Insight from micromechanical modelling2014Inngår i: Journal of Theoretical Biology, ISSN 0022-5193, E-ISSN 1095-8541, Vol. 345, s. 78-91Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Abstract A micromechanical model is presented that predicts the stiffness of wood tissues in their three principal anatomical directions, across various hardwood species. The wood polymers cellulose, hemicellulose, and lignin, common to all wood tissues, serve as the starting point. In seven homogenisation steps, the stiffnesses of these polymers are linked to the macroscopic stiffness. The good agreement of model predictions and corresponding experimental data for ten different European and tropical species confirms the functionality and accuracy of the model. The model enables investigating the influence of individual microstructural features on the overall stiffness. This is exploited to elucidate the mechanical effects of vessels and ray cells. Vessels are shown to reduce the stiffness of wood at constant overall density. This supports that a trade-off exists between the hydraulic efficiency and the mechanical support in relation to the anatomical design of wood. Ray cells are shown to act as reinforcing elements in the radial direction.

  • 180.
    De Magistris, Federica
    et al.
    RISE., STFI-Packforsk.
    Salmen, Lennart
    RISE., STFI-Packforsk.
    Finite element modelling of wood cell deformation transverse to the fibre axis2008Inngår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 23, nr 2, s. 240-246Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Modelling of wet wood under compression and combined shear and compression load was performed to simulate the mechanical pulping of wood chips in refiners. Experiments have shown that the wet fibre network exhibit two different deformation modes; an S-shape mode associated with compression and a brick-shape mode associated with combined shear and compression. To study the factors governing the mechanical behaviour of the fibre network a material model with the characteristics originating from the properties of the wood polymers was developed and was used in a three-dimensional finite element analysis. The effects of material properties were investigated by comparing models with anisotropic one-layer cell walls and orthotropic multi-layer cell walls. The deformation achieved both under compression and under combined shear and compression was found to be similar independent of the material constants used or the number of layers of the cells walls. This implies that the most important factor governing the deformation pattern of the fibre network is the cell structure itself.

  • 181.
    Dedic, D.
    et al.
    RISE, Innventia.
    Iversen, T.
    RISE, Innventia.
    Ek, M.
    Cellulose degradation in the Vasa: The role of acids and rust2013Inngår i: Studies in Conservation, ISSN 0039-3630, E-ISSN 2047-0584, nr 4, s. 308-313Artikkel i tidsskrift (Fagfellevurdert)
  • 182.
    Dedic, D.
    et al.
    RISE, Innventia.
    Iversen, T.
    RISE, Innventia.
    Sandberg, T.
    Ek, M.
    Chemical analysis of wood extractives and lignin in the oak wood of the 380 year old Swedish warship vasa2011Konferansepaper (Fagfellevurdert)
  • 183.
    Dedic, Dina
    et al.
    RISE, Innventia.
    Iversen, Tommy
    RISE, Innventia.
    Ek, M.
    Cellulose degradation in the Vasa: The role of acids and rust2013Inngår i: Studies in Conservation, ISSN 0039-3630, E-ISSN 2047-0584, Vol. 58, nr 4, s. 308-313Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The oak timbers of the Swedish warship Vasa are deteriorating. High amounts of oxalic acid have been found along with a low pH and low molecular weight cellulose deep in the wood timbers. The iron-rich surface wood differs from the interior wood in that it displays higher pH and cellulose with higher molecular weight. The objective of this study was to determine why there is a difference in cellulose degradation, pH, and oxalic acid amount between the surface region and the interior of the Vasa timbers. Analysis of cellulose weight average molecular weight by size exclusion chromatography was performed, as well as quantification of oxalic acid and iron by high-performance anion exchange chromatography and atomic emission spectroscopy, respectively. It was found that a decrease in iron content coincides with an increase in oxalic acid concentration and a drop in pH at a certain depth from the wood surface. When iron-rich surface wood samples from the Vasa were mixed with an aqueous solution of oxalic acid, a fast increase of pH over time was observed. Neither interior wood poor in iron nor the fresh oak reference showed the same neutralizing effect during the time of measurement. This indicates that the presence of iron (rust) causes a neutralization of the wood, through the formation of iron(III) oxalato complexes, thus protecting the wood from oxalic acid hydrolysis. This effect was not observed to the same extent for other acids observed in Vasa wood (sulfuric, formic, glycolic, and acetic acids).

  • 184.
    Dedic, Dina
    et al.
    RISE, Innventia.
    Iversen, Tommy
    RISE, Innventia.
    Ek, Monica
    Cellulose degradation in the Vasa - the role of acids and rust2013Inngår i: Studies in Conservation, ISSN 0039-3630, E-ISSN 2047-0584, Vol. 58, nr 4, s. 308-313, artikkel-id 40105Artikkel i tidsskrift (Fagfellevurdert)
  • 185.
    Dedic, Dina
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Sandberg, Teresia
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Iversen, Tommy
    KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Larsson, Tomas
    Ek, Monica
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Analysis of lignin and extractives in the oak wood of the 17th century warship Vasa2014Inngår i: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 68, nr 4, s. 419-425Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The wood in the 17th century Swedish warship Vasa is weak. A depolymerization of the wood's cellulose has been linked to the weakening, but the chemical mechanisms are yet unclear. The objective of this study was to analyze the lignin and tannin moieties of the wood to clarify whether the depolymerization of cellulose via ongoing oxidative mechanisms is indeed the main reason for weakening the wood in the Vasa. Lignin was analyzed by solid-state nuclear magnetic resonance [cross-polarization/magic-angle spinning (CP/MAS) C-13 NMR] and by means of wet chemical degradation (thioacidolysis) followed by gas chromatography-mass spectrometry (GC-MS) of the products. No differences could be observed between the Vasa samples and the reference samples that could have been ascribed to extensive lignin degradation. Wood extracts (tannins) were analyzed by matrix- assisted laser desorption ionization (MALDI) combined with time-of-flight (TOF) MS and C-13 NMR spectroscopy. The wood of the Vasa contained no discernible amounts of tannins, whereas still-waterlogged Vasa wood contained ellagic acid and traces of castalagin/vescalagin and grandinin. The results indicate that the condition of lignin in the Vasa wood is similar to fresh oak and that potentially harmful tannins are not present in high amounts. Thus, oxidative degradation mechanisms are not supported as a primary route to cellulose depolymerization.

  • 186.
    Deshpande, Raghu
    et al.
    MoRe Research, SE-89122 Örnsköldsvik, Sweden.
    Giummarella, Nicola
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Träkemi och massateknologi. Wallenberg Wood Science Center.
    Henriksson, Gunnar
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Träkemi och massateknologi. Wallenberg Wood Science Center.
    Germgård, Ulf
    Karlstad University, SE-65188 Karlstad, Sweden.
    Sundvall, Lars
    MoRe Research, SE-89122 Örnsköldsvik, Sweden.
    Grundberg, Hans
    Domsjö Fabriker, SE-89186 Örnsköldsvik, Sweden.
    Lawoko, Martin
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Träkemi och massateknologi.
    The reactivity of lignin carbohydrate complex (LCC) during manufacture of dissolving sulfite pulp from softwood2018Inngår i: Industrial crops and products (Print), ISSN 0926-6690, E-ISSN 1872-633X, Vol. 115, s. 315-322Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The presence of covalent bonds between lignin and polysaccharides was investigated in dissolving pulps made with one-stage and two-stage acidic sulfite pulping for 100% pine heartwood raw material. The covalent bonds between lignin and pulp polysaccharides occurred mainly to xylan and glucomannan and were of the phenyl glycosides and γ–esters types. The α-ethers that are common in wood were missing in the studied pulp samples. Based on these findings and known lignin reactions during sulfite pulping, a mechanism explaining the absence of the α-ethers is discussed. It is suggested that the lignin carbohydrate bonds may play a vital role in lignin recalcitrance.

  • 187.
    Dorn, Michael
    et al.
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Bader, Thomas K.
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Non-Linear Connection Models in Timber Engineering2016Inngår i: Proceedings of the 2016 World Conference on Timber Engineering (WCTE) / [ed] J. Eberhardsteiner, W. Winter, A. Fadai, M. Pöll, Vienna University of Technology, Austria , 2016Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In this contribution, a numerical model for connections in engineered timber structures, using specially designed connection elements, is presented. The model considers the non-linear load-displacement relation typical for many types of connections on different levels and is presented on the example of dowel-type connections. The structural levels investigated herein are a) the embedment behaviour of a dowel into wood; b) the behaviour of a singledowel connection; and c) a multi-dowel connection under a general load case typical for structural applications. A special characteristic considered in the formulation of the connector elements is the unloading behaviour, which is characterized by an initial high unloading stiffness but a very low stiffness when the load is fully removed. The latter is due to remaining permanent deformations in the wood as well as in the metal connector. The modelling approach was found to correlate well with experimental data and gave new insight in the behaviour of dowel connections, particularly as regards the unloading and reloading behaviour with alternating load directions on the single-dowel connection scale.

  • 188.
    Dvinskikh, Sergey V.
    et al.
    Royal Institute of Technology KTH, Division of Physical Chemistry and Industrial NMR Centre, SE-100 44 STOCKHOLM, .
    Furó, István
    Royal Institute of Technology KTH, Division of Physical Chemistry and Industrial NMR Centre, SE-100 44 STOCKHOLM, .
    Sandberg, Dick
    Linnéuniversitetet, Fakultetsnämnden för naturvetenskap och teknik, Institutionen för teknik, TEK.
    Söderström, Ove
    Linnéuniversitetet, Fakultetsnämnden för naturvetenskap och teknik, Institutionen för teknik, TEK.
    Moisture content profiles and uptake kinetics in wood cladding materials evaluated by a portable nuclear magnetic resonance spectrometer2011Inngår i: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280, Vol. 6, nr 3, s. 119-127Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We have evaluated the capability of nuclear magnetic resonance (NMR) technology based on small portable magnets for in situ studies of the local moisture content in wood. Low field and low resolution 1H NMR with a unilateral permanent magnet was used to monitor and map the moisture content of wood cladding materials of various types in a spatially resolved manner. The results show that portable NMR equipment based on small open-access permanent magnets can be successfully used for non-invasive monitoring of the moisture content in various extended wood specimens. The moisture content was measured with a depth resolution of 0.2 mm and a maximum penetration depth of 3 mm. This makes the technique suitable for e.g. in situ local moisture content measurements beneath a coating layer in the claddings and it is also possible to relate the moisture level to specific properties of the wood material.

  • 189. Eder, M.
    et al.
    Arnould, O.
    Dunlop, J.W.C.
    Hornatowska, J.
    RISE, Innventia.
    Salmen, L.
    RISE, Innventia.
    Experimental micromechanical characterisation of wood cell walls2013Inngår i: Wood Science and Technology, ISSN 0043-7719, E-ISSN 1432-5225, nr 1, s. 163-182Artikkel i tidsskrift (Fagfellevurdert)
  • 190.
    Eitelberger, Johannes
    et al.
    Vienna University of Technology, Austria.
    Bader, Thomas K.
    Vienna University of Technology, Austria.
    de Borst, Karin
    Vienna University of Technology, Austria.
    Jäger, Andreas
    Vienna University of Technology, Austria.
    Multiscale prediction of viscoelastic properties of softwood under constant climatic conditions2012Inngår i: Computational materials science, ISSN 0927-0256, E-ISSN 1879-0801, Vol. 55, s. 303-312Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper covers the development and validation of a multiscale homogenization model for linear viscoelastic properties of wood. Starting point is the intrinsic structural hierarchy of wood, which is accounted for by several homogenization steps. Using the correspondence principle, an existing homogenization model for the prediction of elastic properties of wood is adapted herein for upscaling of viscoelastic characteristics. Accordingly, self-consistent, Mori–Tanaka, and unit-cell-based techniques are employed, leading to pointwise defined tensorial creep and relaxation functions in the Laplace-Carson domain. Subsequently, these functions are back-transformed into the time domain by means of the Gaver-Stehfest algorithm. With this procedure the orthotropic macroscopic creep behavior of wood can be derived from the isotropic shear behavior of the lignin-hemicellulose phase. A comparison of model predictions for viscoelastic properties of softwood with corresponding experimentally derived values yields very promising results and confirms the suitability of the model.

  • 191.
    Ekevad, Mats
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Huber, Johannes A.J.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Jacobsson, Peter
    Martinsons Träbroar AB.
    Mechanics of stress-laminated timber bridges with butt end joints2017Konferansepaper (Fagfellevurdert)
    Abstract [en]

    A number of variants of single span and three-span stress-laminated timber bridge decks have been studied via finite element simulations and experiments. Glulam beams in the decks were in general shorter than the total length of span which means that there were butt end joints in the decks. The butt end of each beam in a joint was not connected to the other beam which means that each butt end joint reduced the strength and stiffness of the whole of the deck. Results for deflection and stresses were examined for the studied variants in the form of reduction factors for strength and stiffness relative to a deck without butt end joints.

    Factors are shown in diagrams as function of ratio butt end distance/beam width and also butt end distance/span width. Comparison of achieved results with existing Eurocode rules shows that Eurocode rules are not totally appropriate.

  • 192.
    Eliasson, Lars
    Linnéuniversitetet, Fakultetsnämnden för naturvetenskap och teknik, Institutionen för teknik, TEK.
    Ställ krav på virket: Rätt virke för produktion i framtidens trähusfabrik2011Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [sv]

    Denna avhandling behandlar den svenska trähusbranschens behov och möjligheter att erhålla trämaterial med egenskaper som uppfyller de krav som produktion och slutkund ställer. Ett gemensamt problem för den svenska trähusbranschen är de kvalitetsbrister hos det virke sombranschens företag köper för sin produktion, som kan resultera i merkostnader för branschen med 100 MSEK årligen.

    Trähusföretagen uttrycker en viss uppgivenhet över bemötandet från virkesleverantörerna. Virkesleverantörerna å sin sida menar att köparna av trämaterial inklusive företagen i trähusbranschen i ringa utsträckning genomför reklamationer. Avgörande för genomförda virkesaffärer är ofta priset – det blir affär med den som erbjuder lägst pris. Sammantaget innebär detta att det inte blir någon dialog mellan leverantör och köpare som utvecklar synsättet på trämaterialkvalitet.

    Avhandlingsarbetet har bland annat behandlat beredning av träråvaran till färdiga ämnen t.ex. studier vid tillverkning av kvistfria ämnen. Resultatet av arbetet visar på vikten av att genomföra utvärderingar av material och leverantörer. Resultatet visar vidare att kapkostnaden för färdiga träämnen inkl. spill är ca 1/3 av ämneskostnaden. Dock är kostnaden för trämaterialet låg i relation till totalkostnaden för det färdiga huset vilket innebär att ett högre pris för ett virke som fullt ut motsvarar kravspecifikationerna i liten utsträckning påverkar totalkostnaden för huset.

    Råd till trähusbranschen är att ställa krav på virkesråvaran, utvärdera material och leverantörer samt att trähusbranschen ska sikta mot att bli en modern tillverkningsindustri i likhet med de mest framgångsrika inom verkstadsindustrin.

  • 193.
    Eliasson, Lars
    et al.
    Linnéuniversitetet, Fakultetsnämnden för naturvetenskap och teknik, Institutionen för teknik, TEK.
    Sandberg, Dick
    Linnéuniversitetet, Fakultetsnämnden för naturvetenskap och teknik, Institutionen för teknik, TEK.
    Trähusföretag tappar fördel i slarvig tillverkning.2011Inngår i: Husbyggaren, ISSN 0018-7968, nr 7, s. 24-27Artikkel i tidsskrift (Annet (populærvitenskap, debatt, mm))
    Abstract [sv]

    BYGGMETODER Ska trä öka sin konkurrenskraft måste trähusföretag och virkesleverantörer bli bättre på att både ställa och uppfylla kravspecifikationer. Idag kan materialspill och felleveranser uppgå till närmare en femtedel av virkeskostnaden.

    Trähusbranschen står inför ett antal utmaningar. Avgörande är att kunna producera attraktiva bostäder till en kostnad som inte är högre än att människor har råd.

    Trähusföretagen utnyttjar inte fullt ut material och metoder som är anpassade för en effektiv produktion av hus i fabrik. I den kontexten får träets miljöfördelar en underordnad betydelse i konkurrensen med andra mindre miljömässigt uthålliga material.

  • 194. Engelund, E.T.
    et al.
    Salmen, L.
    RISE, Innventia.
    Tensile creep and recovery of Norway spruce influenced by temperature and moisture2012Inngår i: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, nr 8, s. 959-965Artikkel i tidsskrift (Fagfellevurdert)
  • 195.
    Englund, Finn
    et al.
    SP Technical Research Institute of Sweden, Wood Technology.
    Hill, Callum A.S.Militz, HolgerSegerholm, B. KristofferKTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Byggnadsmaterial.
    Proceedings of the Fourth European Conference on Wood Modifications2009Konferanseproceedings (Fagfellevurdert)
  • 196. Eriksson, John
    et al.
    Ormarsson, Sigurdur
    Chalmers University of Technology, Sweden.
    Petersson, Hans
    Växjö universitet, Fakulteten för matematik/naturvetenskap/teknik, Institutionen för teknik och design.
    Adaptive Finite Element Analysis of Non-linear Moisture Flow and Associated Distortion Behaviour in Wood2003Inngår i: ADMOS Conference on Adaptive Modelling and Simulation, 2003Konferansepaper (Fagfellevurdert)
  • 197.
    Eriksson, John
    et al.
    Chalmers University of Technology.
    Ormarsson, Sigurdur
    Chalmers University of Technology.
    Petersson, Hans
    Växjö universitet, Fakulteten för matematik/naturvetenskap/teknik, Institutionen för teknik och design.
    An experimental and numerical study of the shape stability in glued columns2005Inngår i: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 63, nr 6, s. 423-429Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The study concerns the question of how the shape stability features of laminated columns of Norway spruce can be improved in terms of twist through optimal orientation of the individual laminates. Both experimental testing and numerical simulations were employed for evaluating twist stability. In all the columns studied, deformations were measured experimentally at different moisture content levels. A number of columns were also selected for numerical analysis in order to obtain a more thorough understanding of the twist behavior involved, their geometries and material properties of interest being determined. The experimental results showed the twist stability of the columns to be highly dependant upon the internal orientation of the individual laminates. It was also found that high quality columns in terms of shape stability could be manufactured, even when the center-core material has a strong twist tendency. The numerical simulations performed were in close agreement with the experimental results.

  • 198.
    Eriksson, John
    et al.
    Chalmers University of Technology.
    Ormarsson, Sigurdur
    Chalmers University of Technology.
    Petersson, Hans
    Chalmers University of Technology.
    Experimental study of shape stability in glued boards2004Inngår i: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 62, nr 3, s. 225-232Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    An experimental study of shape stability in wooden glued boards was performed to verify certain results of particular interest obtained earlier in numerical simulations. Possibilities for achieving products of good shape stability by gluing boards together in an optimal way are discussed. Since twist is often the most serious form of distortion defects for the user, it was the main type of board deformation considered. Three types of glued products were tested. The experiments show clearly that glued boards can be produced that remain stable in shape when exposed to extreme variations in moisture. The results agree well with the numerical simulations performed earlier. It was found that initial twist could be reduced by proper application of pressure during gluing and that through gluing the occurrence of cracking defects on visible surfaces could be substantially reduced.

  • 199.
    Eriksson, John
    et al.
    Chalmers University of Technology .
    Ormarsson, Sigurdur
    Växjö universitet, Fakulteten för matematik/naturvetenskap/teknik, Institutionen för teknik och design. Chalmers University of Technology .
    Petersson, Hans
    Växjö universitet, Fakulteten för matematik/naturvetenskap/teknik, Institutionen för teknik och design.
    Finite element analysis of coupled nonlinear heat and moisture transfer in wood2006Inngår i: Numerical Heat Transfer, Part A Applications, ISSN 1040-7782, E-ISSN 1521-0634, Vol. 50, nr 9, s. 851-864Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A nonlinear model for analysing heat and moisture flow in wood during drying below the fiber saturation point is presented. The model used considers wood at a macro level without taking the various moisture transports mechanisms at the microscopic level into account. Based on the finite-element method, a coupled system of equations resulting from the adopted heat and moisture transfer equations is established and an iterative scheme is proposed. The numerical procedure is verified by a test example. In a two-dimensional analysis, the influence of the coupling on the combined heat and moisture transfer is studied for a board subjected to a typical kiln-drying condition. How well the results agree with those obtained by introducing a commonly applied simplification is discussed.

  • 200. Escalante, Alfredo
    et al.
    Goncalves, Ana
    Bodin, Aase
    Stepan, Agnes
    Sandstrom, Corine
    Toriz, Guillermo
    Gatenholm, Paul
    Wallenberg Wood Sci Ctr, Chalmers, Sweden.
    Flexible oxygen barrier films from spruce xylan2012Inngår i: Carbohydrate Polymers, ISSN 0144-8617, E-ISSN 1879-1344, Vol. 87, nr 4, s. 2381-2387Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Arabinoglucuronoxylan was extracted from Norway spruce and films prepared by casting from aqueous solution. The sugar analysis and NMR confirmed that the spruce xylan was composed of arabinose, 4-O-methyl-glucuronic acid and xylose in a ratio of 1:2:11 respectively. Substitutions of 4-O-methyl-alpha-D-GlcpA at O-2 and of alpha-L-Araf at O-3 on the xylose backbone were found by NOE analysis. NOE cross-peaks indicated as well that there is at least one free xylose on the main chain present between two substitutions. Whether the distribution of side chains was random or in blocks was uncertain. The average molecular weight of the sample was determined by size exclusion chromatography to be 12,780 g/mol. Arabinoglucoronoxylan casting yielded transparent flexible films with an average stress at break of 55 MPa, strain at break of 2.7% and a Young's Modulus 2735 MPa. Wide-angle X-ray scattering analysis showed that the arabinoglucuronoxylan films were totally amorphous. Addition of sorbitol as plasticizer resulted in less strong but more flexible films (strain at break of 5%). Peaks of crystallinity could be seen in X-ray which corresponds to sorbitol crystallizing in distinct phases. The dynamic mechanical analysis showed that the arabinoglucuronoxylan film softened at a later relative humidity (80% RH) in comparison with plasticized films (60% RH). The films showed low oxygen permeability and thus have a potential application in food packaging.

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