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  • 1.
    Stenudd, Stefan
    Member, Forest Products Society.
    Color response in silver birch during kiln-drying2004Ingår i: Forest products journal, ISSN 0015-7473, Vol. 54, nr 6, 31-36 s.Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Color change in silver birch caused by kiln-drying is a major down-grading factor and has substantial economical impact on high value furniture and flooring production. This study investigates the color responses to process parameters at different stages in the drying process. Samples were dried in a climate chamber and laboratory kilns and the color of dry wood was registered according to the CIE L*C*h color system. The results show that during the capillary drying phase (moisture content > 55 %) time is more important than temperature. Swift initial drying even at elevated temperatures increases the lightness and decreases the saturation. The major color changes occur later on, during the diffusive drying phase from approximately 30 to 20 percent moisture content. Here a combination of temperature, time, and initial moisture content is decisive for the final wood color. Swift drying in both stages even at moderately elevated temperatures results in a highly desirable brighter color.

  • 2.
    Sandberg, Dick
    Linnéuniversitetet, Fakultetsnämnden för naturvetenskap och teknik, Institutionen för teknik, TEK.
    Dick Sandberg, träforskare : kämpar för stående årsringar2004Ingår i: Smålänningen, ISSN 1104-0025, nr 55B, 20-21 s.Artikel, forskningsöversikt (Övrig (populärvetenskap, debatt, mm))
  • 3.
    Blom, Åsa
    et al.
    Växjö universitet, Fakulteten för matematik/naturvetenskap/teknik, Institutionen för teknik och design.
    Bergström, Mikael
    Växjö universitet, Fakulteten för matematik/naturvetenskap/teknik, Institutionen för teknik och design.
    Elowson, Torbjörn
    Durability of Untreated Norway Spruce (Picea abies) Exposed Outdoors Above Ground for Nine Years.2004Ingår i: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 58, nr 2, 167-172 s.Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Moisture dynamics and durability during weather exposure as affected by origin and production method were studied for nine years on 113 untreated spruce samples. The moisture content was measured on 67 occasions. The weight loss was determined for each sample at the end of the sampling period. The most important factors, affecting both moisture content and weight loss, were origin and drying technique. The samples originating from central Sweden had the best durability, followed by the southern stand, while the northern stand had the lowest durability in terms of weight loss. Airdrying had a negative impact on the performance of samples from all three stands, but to different degrees. Samples from the northern stand were most sensitive to airdrying, in terms of both weight loss and moisture content, followed by the southern stand, while the central stand was least sensitive. Why the samples from the northern stand were more sensitive to airdrying and showed the largest weight losses is unknown; it can only be suggested that the origin of the wood can be of importance for the durability.

  • 4.
    Blennow, Kristina
    et al.
    Swedish University of Agricultural Sciences.
    Olofsson, Erika
    Swedish University of Agricultural Sciences.
    Kan man undvika stormskador?2004Ingår i: Osäkerhet och aktiv riskhantering: aspekter på osäkerhet och risk i sydsvenskt skogsbruk / [ed] Kristina Blennow, Alnarp: Sustainable Forestry in Southern Sweden (SUFOR) , 2004, 1, 39-43 s.Kapitel i bok, del av antologi (Övrigt vetenskapligt)
  • 5.
    Sandberg, Dick
    et al.
    Linnéuniversitetet, Fakultetsnämnden för naturvetenskap och teknik, Institutionen för teknik, TEK.
    Johansson, Jimmy
    Växjö universitet, Fakulteten för matematik/naturvetenskap/teknik, Institutionen för teknik och design.
    New production system for the manufacture of high-quality wood with vertical annual rings2004Rapport (Övrigt vetenskapligt)
    Abstract [en]

    The PrimWood method is a production system for sawing hardwood and softwood timber, and for further processing and refining the dried wood into knot-free boards, components and panels with vertical annual rings.

    This article presents an idea for a technical realisation of the PrimWood method. The method has in the first place been adapted to the sawing of quantities which correspond to the available volume of hardwood existing in Sweden, but the system is also well suited for softwood.

    The basis of the production system is that the log is sawn according to the star-sawing pattern in a vertical band saw with a carriage. The carriage is fitted with equipment for rotating and changing the position of the log or log parts in the vertical or horizontal directions in order to make it possible to saw pieces of wood with either a rectangular or a triangular cross-section.

    After it has been dried by conventional methods, the sawn wood is further processed by cross cutting, jointing, planing and gluing into knot-free components with vertical annual rings.

    The system seems to be well adapted to the conditions which apply in the small-scale processing of hardwood and softwood, and high-quality products can be produced with a high volume yield.

  • 6.
    Stenudd, Stefan
    Växjö universitet, Fakulteten för matematik/naturvetenskap/teknik, Institutionen för teknik och design.
    Colour response of Silver birch to press drying2003Ingår i: Proceedings of the 8th International IUFRO Wood DryingConference, 2003, 449-454 s.Konferensbidrag (Refereegranskat)
    Abstract [en]

    Press drying is a rapid drying technique capable of reducing deformation, but also known to cause discolourationin some wood species. The colour of Silver birch is of great importance to the furniture and flooring industry, wherethe blond colour is highly appreciated. This study investigates the colour response in the core of 36 mm Silver birchsamples to the process variables: plate temperature, plate pressure and air pressure and to the material variable initialmoisture content. Short samples were press dried in a electrically heated laboratory press to approximately 10%moisture content and the interior colour of dry wood was registered according to the CIE L*C*h colour system. Theresults show that plate temperature is the most influential process variable controlling the wood colour. Hightemperature results in brighter more yellowish colour and reduced drying time. Other process and material variablesalso have some influence on the final colour but their contributions are smaller. Press drying of green wood at 170Cin normal atmospheric air pressure gave a wood colour comparable to that of conventionally kiln dried birch wood,only slightly darker and more reddish. The study indicates that press drying of Silver birch is possible from a colourperspective by careful selection of process parameters.

  • 7.
    Adamopoulos, Stergios
    et al.
    Aristotle University, Greece.
    Voulgaridis, Elias
    Aristotle University, Greece.
    Dimensional changes of extracted and non-extracted small wood specimens of black locust (Robinia pseudoacacia L.)2003Ingår i: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 61, nr 4, 264-268 s.Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    From straight grained heartwood of black locust (Robinia pseudoacacia L.), specimens, 3 cm×3 cm in cross section and 0.5 mm (or 10 mm) in axial direction, were cut and used for the determination of dimensional changes and the rate of tangential swelling. Mean radial, tangential and axial shrinkage was 5.30%, 6.67% and 0.16%, respectively, while the coefficient of anisotropy was 1.26. Half of the specimens for the determination of the rate of tangential swelling were extracted for 48 h with distilled hot water. The tangential dimensional change and the time taken to attain half maximum swelling in air-dry and oven-dry specimens were assessed according to a common technique. Extractive removal resulted in an increase of the total magnitude of tangential swelling in both air-dry and oven-dry specimens. However, no significant differences in time taken to attain half maximum swelling between air-dry and oven-dry specimens were observed after extraction. The rate of tangential swelling was lower in air-dry specimens than in oven-dry specimens after 30 min of immersion in water when were non-extracted and after 5 min of immersion in water when were extracted. Extracted air-dry specimens had a greater rate of tangential swelling than non-extracted air-dry specimens and the same occurred for oven-dry specimens. Extraction resulted in a higher diffusion coefficient for air-dry specimens. The diffusion coefficient calculated for non-extracted air-dry specimens (0.901×10−4 cm2/min) showed that black locust is a difficult species to impregnate.

  • 8.
    Eklund, Leif
    et al.
    Växjö universitet, Fakulteten för matematik/naturvetenskap/teknik, Institutionen för biovetenskaper och processteknik.
    Säll, Harald
    Växjö universitet, Fakulteten för matematik/naturvetenskap/teknik, Institutionen för industriella produktionssystem.
    Linder, Sune
    Swedish University of Agricultural Sciences, Sweden.
    Enhanced growth and ethylene increases spiral grain formationin Picea abies and Abies balsamea trees2003Ingår i: Trees, ISSN 0931-1890, E-ISSN 1432-2285, Vol. 17, nr 1, 81-86 s.Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Spiral grain angle in Norway spruce (Piceaabies) trees and balsam fir (Abies balsamea) seedlingswas investigated in relation to growth rate, endogenousand applied ethylene. Trees from stands of Norwayspruce, which were irrigated and fertilised in order to enhancegrowth, and trees having different growth rates innon-treated stands were studied. Stem growth rate at thestand level (m3 ha–1 year–1) was measured annually, orby means of microscopy on stem sections as the numberand size of tracheids produced. Enhanced growth increasedethylene evolution and maintained a high levelof left-handed spiral grain angle in comparison to slower-growing trees. An increased number of earlywoodtracheids in fast growing trees was correlated to a moreleft-handed spiral grain angle. Ethrel, applied to stems ofbalsam fir seedlings, increased the internal ethylene levelsin parallel with increased left-handed spiral grain angle.The results indicate that ethylene regulates the extentof spiral grain angle.

  • 9.
    Blennow, Kristina
    et al.
    Swedish University of Agricultural Sciences, Sweden.
    Olofsson, Erika
    Swedish University of Agricultural Sciences, Sweden.
    Sallnäs, Ola
    Swedish University of Agricultural Sciences, Sweden.
    Evaluating WINDA: a tool for assessing the probability of wind damage to forest stands2003Ingår i: Proceedings of the International Conference Wind Effects on Trees: 16-18 September 2003, University of Karlsruhe, Germany / [ed] B. Buck, C. Kottmeier, C., Mattheck, C. Quine, G. Wilhelm, 2003, 137-144 s.Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    WINDA is an integrated system of models for calculating the stand-wise probability of wind damage of trees within a landscape (Blennow & Sallnäs, submitted). It integrates a modified version of the dose/response model HWIND (Peltola et al., 1999), the airflow model WASP (Mortensen et al., 1998), and a component for calculating the zero-plane displacement and surface roughness. WINDA uses a GIS for geographical computations. The calculations are made point-wise at exposed stand edges and the results are combined for each stand. The likelihood of damage is calculated using extreme value theory. The mechanistic modelling approach makes WINDA useful for evaluating effects on the probability of wind damage of silvicultural treatments and forestry activities as well as of a changed climate. This paper briefly outlines WINDA and evaluates output by comparing predicted damage with observed damage for two landscapes in southern Sweden.

  • 10.
    Hannrup, Björn
    et al.
    Skogforsk.
    Säll, Harald
    Växjö universitet, Fakulteten för matematik/naturvetenskap/teknik, Institutionen för teknik och design.
    Jansson, Gunnar
    Skogforsk.
    Genetic parameters for spiral grain in Scots pine and Norway spruce2003Ingår i: Silvae Genetica, ISSN 0037-5349, Vol. 52, nr 5-6, 215-220 s.Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Genetic parameters were estimated for grain angle, growth and exterior quality traits in two 18-year-old Scots pine (Pinus sylvestris L.) progeny trials and for grain angle and growth traits in two 12-year-old clonal trials of Norway spruce (Picea abies L. Karst.). Mean grain angles ranged 1.4 to 2.0 degrees and 2.1 to 2.6 degrees in the Scots pine and Norway spruce trials, respectively. Heritabilities for grain angle were high in Scots pine (h2>0.40) and moderate in Norway spruce (H2>0.30). The genetic standard deviations were around or slightly below one degree. In general, grain angle was genetically and phenotypically uncorrelated with the growth and exterior quality traits. All traits showed low amount of genotype by environment interaction and there was no tendency of grain angle being a more stable traits than the other traits studied.

     

    A newly developed measurement device for grain angle where the grain angle is revealed by a wedge that is pushed through the bark into the wood and follows the inclination of the tracheids was tested and found suitable for measurements in genetic tests.

  • 11.
    Sandberg, Dick
    Linnéuniversitetet, Fakultetsnämnden för naturvetenskap och teknik, Institutionen för teknik, TEK.
    Ny träteknik höjer värdet på skogen.2003Ingår i: Smålandsposten, ISSN 1104-0009, Vol. 20 juni, nr 40, 20-21 s.Artikel, forskningsöversikt (Övrig (populärvetenskap, debatt, mm))
  • 12.
    Sandberg, Dick
    Linnéuniversitetet, Fakultetsnämnden för naturvetenskap och teknik, Institutionen för teknik, TEK.
    Radially sawn timber: - a new manufacturing system for the wood industry2003Ingår i: Research Conference of Industrial Competitiveness, Växjö October 29, 2003, Växjö: Växjö University , 2003Konferensbidrag (Refereegranskat)
    Abstract [en]

    A new manufacturing system, the PrimWood Method, has been proposed to improve the utilization of wood.  A basic concept within this method is the sawing pattern called star sawing, which produces timber with both rectangular and triangular cross sections. This method facilitates an efficient production of radially sawn timber with vertical annual rings, without juvenile wood.

    The sawn timber produced in the PrimWood Method is used to produce high quality, knot-free solid wood panels with vertical annual rings.  In this process, the timber is finger jointed to form knot-free lengths which are glued together into a block.  This block can then be divided according to thickness into thinner panels with vertical annual rings.  In star-sawing, a certain volume of clear pieces are obtained which are relatively long, i.e. longer than 1 metre. It is not desirable to finger-joint these pieces, but instead to use them to manufacture products without any finger-joint.

    The PrimWood Method has been tested in an industrial plant. The manufacturing system was designed for a sawing capacity of about 30 000 m3 logs, which corresponds to 16 800 m3 of star-sawn timber per shift per annum.  The production of solid wood panel was then designed to give a volume of 5 800 m3 per annum.

  • 13.
    Blomqvist, Lars
    et al.
    Trätek.
    Hagström, Lina
    Trätek.
    Oscarsson, Jan
    Trätek.
    3D-modeller i träindustrin som konkurrensmedel vid e-handel2002Rapport (Övrigt vetenskapligt)
  • 14.
    Passialis, C
    et al.
    Aristotelian University, Greece.
    Adamopoulos, Stergios
    Aristotelian University, Greece.
    A comparison of three NDT methods for determining the modulus of elasticity in flexure of fir and black locust small clear wood specimens2002Ingår i: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 60, nr 5, 323-324 s.Artikel i tidskrift (Refereegranskat)
  • 15. Blom, Åsa
    et al.
    Bergström, Mikael
    Beständighet hos svenskt barrvirke vid applikationer ovan mark2002Rapport (Övrigt vetenskapligt)
  • 16.
    Adamopoulos, Stergios
    Aristotelian University, Greece.
    Flexural properties of black locust (Robinia pseudoacacia L.) small clear wood specimens in relation to the direction of load application2002Ingår i: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 60, nr 5, 325-327 s.Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Values of pure moduli of elasticity (PMOE), experimental modulus of elasticity (MOE) in static bending and moduli of rigidity (GLR, GLT) were calculated in juvenile and mature black locust defect-free small wood specimens after loading in static bending alternately on true radial and tangential surfaces. For both juvenile and mature specimens, no significant differences (t-test, 95% probability level) were found between the radial and tangential moduli of elasticity and rigidity. Values of PMOE were found to be 27–32% higher than the corresponding values of MOE at the 15:1 span-to-depth ratio.

  • 17.
    Adamopoulos, Stergios
    Aristotelian University, Greece.
    Influence of hot-water extractives on radial and tangential shrinkage of black locust wood (Robinia pseudoacacia L.)2002Ingår i: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 60, nr 5, 377-378 s.Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    IntroductionRemoval of extractives increases the shrinkage and swelling of wood (Nearn 1955, Salamon and Kozak 1968, Cooper 1974, Taylor 1974). The effect of progressive extraction on the above properties has not been investigated much. In oak (Quercus conferta L.), a forest species rich in extractives, the shrinkage progressively increased with progressive extraction (Voulgaridis et al. 1980). In black locust (Robinia pseudoacacia L.), much of the main-stem volume is comprised of heartwood, characterized by the presence of dark yellow-brown extractives. While the extractives of black locust give the heartwood its distinctive color and decay resistance, they comprise only 6.2 to 8.3% of the dry weight of the main stem (Stringer 1992). Hot-water extractives range from 5.2 to 8.6% (Hart 1968, So et al. 1980). The present study was primarily undertaken to determine whether the progressive removal of hot-water extractives affects the radial and tangential shrinkage of black locust heartwood.

  • 18. Thuvander, F
    et al.
    Kifetew, G
    Berglund, L A
    Modeling of cell wall drying stresses in wood2002Ingår i: Wood Science and Technology, ISSN 0043-7719, E-ISSN 1432-5225, Vol. 36, nr 3, 241-254 s.Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    All applications of wood involve drying the material from the green state. The cell wall may be viewed as a laminate consisting of different layers. The layers have different orientations and therefore different moisture expansion characteristics. As a result, stresses will develop in the layers due to drying. Micromechanical models for fibre composite materials were used in combination with a laminate analogy in order to calculate these drying stresses in the cell wall layers S1, S2 and S3. Resulting stresses were very high. In reality viscoelastic effects will significantly reduce stresses at high moisture content. However, at lower moisture content irreversible cell wall damage is likely to form as a result of the stresses computed by the model.

  • 19.
    Gjerdrum, Peder
    et al.
    Norwegian Forest Research Institute, Norway.
    Säll, Harald
    Växjö universitet, Fakulteten för matematik/naturvetenskap/teknik, Institutionen för industriella produktionssystem.
    Storö, Hans Martin
    North Tröndelag Research Institute, Norway.
    Spiral grain in Norway spruce: constant change in grain angle in Scandinavian sawlogs2002Ingår i: Forestry (London), ISSN 0015-752X, E-ISSN 1464-3626, Vol. 75, nr 2, 163-170 s.Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Any evident grain deviation will reduce strength and increase warp in sawn timber. To describe the magnitude and variance of grain angle in Norway spruce, specimens from 1046 Norwegian sawlogs and 380 logs from Sweden and Finland were examined. For individual specimens, grain angle outside the innermost zone closest to the pith might be expressed by a simple linear function of radial distance from the pith. The intercept and inclination of this function are close to bivariate normally distributed with mean values (SD) of 2.7° mm−1 (1.9) and −0.039° mm−1 (0.037), respectively. Inclination is less negative for wider annual rings (r = 0.3), and intercept and inclination are negatively correlated (r = −0.4). The constant rate of change indicates inherited property rather than influence of any dynamic, external stimulus. No predictor for grain angle pattern was found. The linear model leads to simplifications both when observing the grain angle in the forestry, and in calculations of strength properties and distortion in the timber industry.

  • 20.
    Blomqvist, Lars
    et al.
    Trätek.
    Bronsek, Anders
    Trätek.
    Oscarsson, Jan
    Trätek.
    Svensson, Nils
    Trätek.
    Säkerhet och organisation vid CNC-maskiner i träindustrin2002Rapport (Övrigt vetenskapligt)
  • 21.
    Adamopoulos, Stergios
    et al.
    Aristotelian University, Greece.
    Voulgaridis, Elias
    Aristotelian University, Greece.
    Within-tree variation in growth rate and cell dimensions in the wood of black locust (Robinia pseudoacacia)2002Ingår i: IAWA Journal, ISSN 0928-1541, Vol. 23, nr 2, 191-199 s.Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Black locust (Robinia pseudoacacia L.) is regarded as an important natural resource almost throughout the world but relatively little is known about the within-tree variability of the anatomical characteristics of its wood. Discs 2 cm thick were cut at 2.25 m intervals, from the ground level to the top from ten black locust trees, 18–37-years-old, from the University Forest of Taxiarchi, Chalkidiki, Greece. The discs were used for the determination of growth rate and cell dimensions (fiber length and vessel member length and diameter) and their withintree variability (radial, oblique, vertical). Growth rate increased within the first 5–9 growth rings from the pith and then gradually decreased. Oblique variation of growth rate did not exhibit any clear tendency but a decrease at the top. In the case of vertical variation, growth rate decreased gradually with the year of cambium formation. Radial variability curves were found to be typical for the dimensions of cells (fibers, vessel members) especially for the fiber length. A rapid increase in cell dimensions was observed in the first 7–11 growth rings, the juvenile zone. Oblique and vertical variation of cell dimensions did not exhibit any clear tendencies.

  • 22.
    Kifetew, Girma
    et al.
    Linnéuniversitetet, Fakultetsnämnden för naturvetenskap och teknik, Institutionen för teknik, TEK.
    Larsson, Hanna
    Wood Technology.
    Axial Twist in Wood: a Comparison between Experimental result and Theoretical Calculation2001Ingår i: Proceedings of the First International Conference of the European Society for Wood Mechanics: April 19th-21st, 2001, Lausanne, Switzerland / [ed] P. Navi, Lausanne, Switzerland, 2001, 495-503 s.Konferensbidrag (Refereegranskat)
  • 23.
    Stenudd, Stefan
    Linköping University.
    Colour changes in birch and beech during kilndrying2001Ingår i: Proceedings of the 7th International IUFRO Wood DryingConference, 2001, 300-305 s.Konferensbidrag (Refereegranskat)
    Abstract [en]

    The aim of this study was to investigate the colour responses of Silver Birch (Betula pendula Roth.) and Beech(Fagus sylvatica L.) during conventional kiln-drying at industrial used conditions. The response of dryingtemperature, relative humidity, initial moisture content and board thickness on wood colour was investigated in two24 factorial designed experiments. The method was used to investigate and rank the effects of the variables and allpossible combinations of the variables with a minimum of tests. A total number of 224 clear green sapwood samplesdivided in to 32 groups were kiln-dried below 20% in a climate chamber, followed by room climate drying toapproximately 8%. Colour measurements were conducted on dry planed samples using a photoelectric colorimeterand results were expressed in the CIE L* (lightness) C* (chroma) h (hue) colour space. A comparison was also madewith 32 samples dried in room climate from green to 8%, differences were calculated and expressed as CIE (ΔE*ab)effects. The factorial experiments used high and low level for investigating the variables: temperature (60/30C),relative humidity (82/62%), initial moisture content (green/30%) and wood thickness (16/10 mm).Experimental results showed that drying temperature is the most important factor for the colour responses in theinvestigated intervals for both birch and beech. The second most important factor, for both species, was thickness ofthe wood. Relative humidity was found to be the third most important factor. Both species reacted in a similar way toincreasing temperature, thicker dimensions and high relative humidity. The wood colour became darker, moresaturated and redder compared to the reference material. The colour response effects were larger on birch comparedto beech.

  • 24.
    Hameed, Mahmood
    et al.
    Georg-August-Universität Göttingen, Germany.
    Roffael, Edmone
    Georg-August-Universität Göttingen, Germany.
    Eindringtiefe verschiedener Bindemittel in Splintholz- und Kernholzspänen der Kiefer (Pinus sylvestris L.): [On the penetrability of various glues from sap- and heartwood of Pine (Pinus sylvesteis L.)]2001Ingår i: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 58, nr 6, 432-436 s.Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Investigation of the penetrability of various glues [urea-formaldehyde resin (UP-resin), phenol-formaldehyde resin (PP-resin), melamine-urea-phenol-formaldehyde made of pine sapwood and heartwood revealed: the various glues penetrate chips from pine sapwood regardless of tree age, height of the sample studied and surface structure deeper than in those made of heartwood. The various glues more deeply penetrate chips from sapwood and heartwood of the 48-year-old pine than chips from sapwood and heartwood of the 124-year-old pine. The penetrability of various glues in chips from sapwood and heartwood of the 124-year-old pine increases with increasing height of the sample studied. Moreover,  glues penetrate sanded surfaces of chips from sapwood and heartwood of the 48- und the 124-year-old pine to a lesser extent than unsanded chip surfaces.

  • 25. Adamopoulos, Stergios
    et al.
    Voulgaridis, Elias
    Passialis, C.
    Wood quality characteristics of black locust (Robinia pseudoacacia  L.)2001Ingår i: Forest Research - New Series, Vol. 14, 63-72 s.Artikel i tidskrift (Refereegranskat)
  • 26.
    Kifetew, Girma
    et al.
    Linnéuniversitetet, Fakultetsnämnden för naturvetenskap och teknik, Institutionen för teknik, TEK.
    Sandberg, Dick
    Kungliga Tekniska högskolan (KTH).
    Material damage due to electron beam during testing in the environmental scanning electron microscope (ESEM).2000Ingår i: Wood and Fiber Science, ISSN 0735-6161, Vol. 32, nr 1, 44-51 s.Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This study describes the development of cell-wall damage, i.e., the creation of cracks across or in the vicinity of pits during the testing of twenty microtomed spruce (Picea abies karst.) samples in the Environmental Scanning Electron Microscope (ESEM). Samples were investigated both in an unloaded condition and under a constant tensile load and at different moisture levels. Regions of the moisture-cycled samples that had been exposed to an electron beam during image acquisition showed damage running through pits and their surroundings. Specimens loaded in the green condition and dried in the chamber for 2 h without beam exposure except during imaging showed no noticeable cell-wall damage. The results indicate that the electron beam may be a major source of damage initiation. Therefore, it is essential to note the circumstances of the rest when explaining the observations made in ESEM studies.

  • 27. Kifetew, G
    et al.
    Sandberg, D
    Material damage due to electron beam during testing in the Environmental Scanning Electron Microscope (ESEM)2000Ingår i: Wood and Fiber Science, ISSN 0735-6161, Vol. 32, nr 1, 44-51 s.Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This study describes the development of cell-wall damage, i.e., the creation of cracks across or in the vicinity of pits during the testing of twenty microtomed spruce (Picea abies karst.) samples in the Environmental Scanning Electron Microscope (ESEM). Samples were investigated both in an unloaded condition and under a constant tensile load and at different moisture levels. Regions of the moisture-cycled samples that had been exposed to an electron beam during image acquisition showed damage running through pits and their surroundings. Specimens loaded in the green condition and dried in the chamber for 2 h without beam exposure except during imaging showed no noticeable cell-wall damage. The results indicate that the electron beam may be a major source of damage initiation. Therefore, it is essential to note the circumstances of the rest when explaining the observations made in ESEM studies.

  • 28.
    Ormarsson, Sigurdur
    et al.
    Chalmers University of Technology.
    Petersson, Hans
    Chalmers University of Technology.
    Dahlblom, Ola
    Lund University.
    Numerical and experimental study of compression wood influence on drying timber distortion2000Ingår i: Drying Technology, ISSN 0737-3937, E-ISSN 1532-2300, Vol. 18, nr 8, 1897-1919 s.Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In timber exposed to moisture variations, drying distortions is a serious problem that might result into sawn timber and other wood products unsuitable for construction purposes. Two characteristics of wood are that its behaviour is strongly orthotropic and that it is very sensitive to variations in moisture content. In addition, wood is characterised by variation in its properties from pith to bark. A further important property of wood, which affects its behaviour, is its spiral grain. For timber containing much compression wood the drying distortions are also highly dependent upon where the compression wood is located in the sawn boards. The present study concerns an experimental investigation of density, grain angles, shrinkage parameters and longitudinal elastic modulus in a number of spruce boards containing much compression wood. On the basis of the data obtained, numerical simulations have been carried out in order to determine the deformations that developed in the boards during changes in moisture content.

  • 29.
    Eklund, Leif
    et al.
    Växjö universitet, Fakulteten för matematik/naturvetenskap/teknik, Institutionen för biovetenskaper och processteknik.
    Säll, Harald
    Växjö universitet, Fakulteten för matematik/naturvetenskap/teknik, Institutionen för teknik och design.
    Kliger, Robert
    Chalmers University of Technology, Sweden.
    Spiral grain from an environmental, genetic and economical point of view2000Ingår i: The Tree, 2000Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    Characteristic of wood is that its behavior is strongly orthotropic due to the internal structure of the material and dependent on moisture and temperature. In addition, the material is characterized by a strong variation of the properties in the radial direction.  Another important property that affects the behavior of wood is spiral grain, causing the direction of the fibers to deviate from the longitudinal direction of the tree. It is hardly possible to assess spiral grain in the woods, no rejection of severe spiraled trees are done before the log arrives into the sawmill. If a method for on site rejection is available, and the severest spiraled trees, 2-10%, could be avoided in the shipment to the sawmill substantial money could be saved in the forest industry. The causes of spiral grain have been thoroughly discussed through the years and the debate about the environmental and genetic impact on the phenomenon is still not settled. We present evidence for a direct effect of wind on the degree of spiral grain. We also present evidence for a putative thinning effect on spiral grain that is probably connected to wind. Additionally we also present evidence for a strong genetic impact on the formation of spiral grain in conifer trees. In another study mechanical properties such as shape stability has been investigated for the same trees. In some of the logs it may therefore be possible to quantify the relation between spiral grain and distortion in sawn timber.

  • 30.
    Kliger, Robert
    et al.
    Chalmers University of Technology, Sweden.
    Säll, Harald
    Växjö universitet, Fakulteten för matematik/naturvetenskap/teknik, Institutionen för teknik och design.
    STUD: Improved Spruce Timber Utilizations: Prediction of Twist and Industrial Validation. Sub-task B9.1.2000Rapport (Övrigt vetenskapligt)
    Abstract [en]

    It has been shown that the number of straight battens after drying can be easily increased by avoiding converting logs with a somewhat large left-hand spiral grain measured under bark and by avoiding converting the central cylinder of logs with a diameter about 50 mm around the pith. It is assumed that more than 10% of the trees (Norway spruce) exceed a spiral grain angle of 3° measured under bark. Between 80% and 90% of the studs from these trees displayed an unacceptable amount of twist (3°). It should be of great interest for the sawmill industry to be able to reject logs with respect to their overly large spiral growth in order to improve the straightness of sawn lumber in service (at low moisture content).

    Other conclusion drawn from this study is that the spiral grain angle and the annual ring curvature of the stud can predict twist. If it is possible to measure effectively spiral grain angle on the logs or on the sawn timber prior to drying the twist-prone material would be possible to sort out and thus increase the value of the timber products. Simple models expressed in diagram form can produce enough information about twist to be a useful tool for improving the number of straight studs after drying.

    Over 90% of the studs sawn closer than 50 mm from the pith from five trees displayed unacceptable twist when dried to 12% moisture content. All the studs sawn from a tree (five logs) with a left-hand spiral grain of about 15° displayed very large twist after drying and they were all classified as rejects, independent of the grading criterion. 

  • 31.
    Eklund, Leif
    et al.
    Växjö universitet, Fakulteten för matematik/naturvetenskap/teknik, Institutionen för biovetenskaper och processteknik.
    Säll, Harald
    Växjö universitet, Fakulteten för matematik/naturvetenskap/teknik, Institutionen för industriella produktionssystem.
    The influence of wind on spiral grain formation in conifer trees2000Ingår i: Trees, ISSN 0931-1890, E-ISSN 1432-2285, Vol. 14, 324-328 s.Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The correlation between spiral grain formationand crown asymmetry was investigated in 18 Scots pine(Pinus sylvestris L.) and 17 Norway spruce [Picea abies(L.) Karst.] trees selected from clones of each speciesgrowing in the south of Sweden. The angle between thelongitudinal direction of the tracheids in the outermostyear ring compared to the longitudinal direction of thestem was measured by scribing lines which followed thedirection of the tracheids. The crown asymmetry wasmeasured by taking photographs of the trees followed bya simple picture analysis of the tree. Wind data for thegrowing seasons of 1997 and 1998 were obtained fromthe Swedish Meteorological and Hydrological Institute.The results showed a significant correlation between theangle of the tracheids compared to the stem longitudinaldirection going from a left-handed angle if the trees hada crown projected to the north towards a right-handedangle the more the crown projects to the south.

  • 32.
    Hameed, Mahmood
    et al.
    University of Göttingen, Germany.
    Roffael, Edmone
    University of Göttingen, Germany.
    Voruntersuchungen zum Einfluß der anatomischen Schnittrichtung auf die Verleimbarkeit des Splint- und Kernholzes der Kiefer (P. sylvestris L.): [Influence of anatomical Wood section on the Gluing of Sap- and heartwood of Pine (Pinus sylvestris L.) with UF-resins]2000Ingår i: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 58, nr 5, 306-307 s.Artikel i tidskrift (Refereegranskat)
    Abstract [de]

    Die Scherfestigkeitswerte von UF-Harz-gebundenem Kiefernsplint- und -kernholz sind in Abhängigkeit von der anatomischen Richtung in der Tabelle 2 zusammengestellt. Daraus geht hervor:

    1. Die Scherfestigkeit der Klötzchenpaare  aus dem Splintholz ist höher als die des Kernholzes  in den entsprechenden anato-mischen Richtungen.

  • 33. Voulgaridis, E
    et al.
    Passialis, C
    Adamopoulos, Stergios
    Wood quality characterization in black locust of different origin2000Ingår i: 3rd Workshop of COST Action E10: Wood properties for Industrial Use “Measuring of wood properties, grades and qualities in the conversion chains and global wood optimization”, 19-21 June, Espoo, Finland, 2000, 147-162 s.Konferensbidrag (Övrigt vetenskapligt)
1 - 33 av 33
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