Change search
Refine search result
1 - 13 of 13
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Rows per page
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sort
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
Select
The maximal number of hits you can export is 250. When you want to export more records please use the 'Create feeds' function.
  • 1.
    Danvind, Jonas
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Analysis of drying wood based on nondestructive measurements and numerical tools2005Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Improved understanding of moisture and mechanical behaviour is a general objective for wood drying research. The main objective of this doctoral thesis was to develop nondestructive experimental methods suitable for collecting valuable response data related to the moisture behaviour and mechanical behaviour of drying wood and to refine this information into modelling parameters. A method for simultaneous noncontact measurement of two-dimensional surface deformations and interior densities was developed. This was done using Digital Speckle Photography (DSP) and X-ray Computed Tomography (CT). Displacements and densities were used for calculation of strain and of moisture content. Experimental tests of the measurement method were done on cross sections of Scots pine. The following accuracy was stated for different properties: A typical calculated displacement error of approximately 10 micrometre was found. Strains derived from the displacements had a maximal error of 1.11 mstrain. Moisture content measuring accuracy was estimated to +-1.8% moisture content at a significance level of 0.05 in a measuring volume with the approximate size 2 x 2 x 1.5 mm3. A similar noncontact technique based only on X-ray CT scanning was developed. Displacements were then estimated from boundary movements of an object in CT images. The estimated standard deviation of the measured moisture content error for this method was 0.04% moisture content. The mean error was unknown. Two different approaches to determining moisture diffusion coefficients from the studied data were presented. The first was based on minimizing the difference between measured and computed values through an optimization scheme. This approach required an initial assumption of the functional form of the diffusion coefficient. The second approach calculated diffusion and mass transfer coefficients through direct finite difference calculations on measured moisture content data. Results on Norway spruce showed interesting local variations of the diffusion coefficient, especially near the evaporation surface. Comparisons between measured and FEM simulated data showed good results. An example showed that a multivariate method of analysis could be an effective and easy-to-use tool for untangling relationships between variables and for generating information from data. Finally, it could be stated that the methods presented will be of use to improve the understanding of the behaviour of drying wood, with the focus on moisture and mechanical properties.

  • 2. Danvind, Jonas
    Measuring strain and moisture content in a cross section of drying wood using Digital Speckle Photography and Computerised X-ray Tomography2003In: Proceedings of the 13th International Symposium on Nondestructive Testing of Wood: August 19-21, 2002, University of California, Berkeley Campus, California, USA / [ed] Frank C. Beall, Madison, Wis.: Forest Products Society, 2003Conference paper (Refereed)
  • 3.
    Danvind, Jonas
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Methods for collecting and analysing simultaneous strain and moisture data during wood drying2002Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Improved understanding of moisture and mechanical behaviour is an international objective for wood drying research. The main objective of this licentiate thesis work was to develop an experimental method suitable for collecting valuable response data related to the moisture and mechanical behaviour of drying wood. Another objective was to provide an example on how multivariate methods can be used to analyse response data. A method for simultaneous non contact measuring of two dimensional surface deformations and interior densities have been developed. This was done using Digital Speckle Photography, DSP, and X-ray Computerised Tomography (CT). Displacements and densities were used for calculation of strains and moisture contents using a custom software developed in Matlab. Experimental tests of the measuring method were made on cross sections of Scots pine. The following accuracy was stated for different properties: - Displacements measured with DSP could be measured with a random error down to 0.01 pixels. A more typical calculated displacement error of approximately 10 micrometres, was found in paper I. - Strains derived from the displacements had a maximal error of 1.11 mstrain in an experimental test in paper II. - Accuracy in density measurements was expected to be less than +-6 kg/m3 for wet wood with moisture contents ranging from 6-100% and less than +-2 kg/m3 in dry wood, at a significance level of 0.05. This was estimated for a 2x2x1.5 mm3 measuring volume. - Moisture content measuring accuracy was estimated by simulations in paper II, which resulted in a measuring accuracy of +-1.8% moisture content at a significance level of 0.05 in a measuring volume with the approximate size of 2x2x1.5 mm3. A multivariate analysing method has been used to present an example on multivariate modelling of shrinkage behaviour in Radiata pine. The method was found to be an easy-to-use tool and useful for valid prediction of radial, tangential, longitudinal and volume shrinkage in the moisture range between 0% and 22% moisture content of the studied wood. The method also proved to be effective for untangling relationships between variables and generating information out of data. Finally, it can be stated that the developed measuring technique and the tested multivariate analysing method will be of use to improve the understanding of the behaviour of drying wood, focusing on moisture and mechanical properties.

  • 4.
    Danvind, Jonas
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    PLS prediction as a tool for modeling wood properties2002In: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 60, no 2, p. 130-140Article in journal (Refereed)
    Abstract [en]

    During an earlier study, material responses of shrinkage and deformation during air-drying were measured on small wood specimens cut from the cross section of a Pinus radiata log. In this paper the analysis of the collected data and the modeling of studied responses were done using multivariate methods. A first model with all variables and all 104 observations was created. In this model there were observations that deviated from the rest and some of them were therefore excluded from further modeling. Also, weak variables and undesired variables were excluded from further modeling. After these exclusions, 77 observations of wood responses below fiber saturation point remained. The results showed good modeling of radial, tangential and volumetric shrinkage between 0-22% MC, with explained variance (R2) and predicted variance (Q2) at approximately 0.9, and moderate modeling of longitudinal shrinkage, R2 = 0.67 and Q2 = 0.65. It was also shown that longitudinal shrinkage has weak correlation to density-related variables in the studied wood. No model with good predictability of deformation was found. This study showed that PLS prediction modeling of shrinkage and deformation in studied wood samples was found to be an effective and easy-to-use tool for untangling relationships between variables and generating information from data.

  • 5.
    Danvind, Jonas
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Ekevad, Mats
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Local water vapor diffusion coefficient when drying Norway spruce sapwood2006In: Journal of Wood Science, ISSN 1435-0211, E-ISSN 1611-4663, Vol. 52, no 3, p. 195-201Article in journal (Refereed)
    Abstract [en]

    In this article, a one-dimensional and a two-dimensional approach to the evaluation of local diffusion coefficients for Norway spruce sapwood from measured moisture content (MC) values are presented. A studied wood sample was dried from the initial green condition to about 15% mean MC, but here only the diffusive part of the drying process between approximately 25% and 15% mean MC was treated. Measured local MC values were based on nondestructive X-ray computed tomography data. Finite element calculations were performed with two alternative diffusion coefficients to test the appropriateness of the diffusion coefficients that were evaluated from the measured MC values. The evaluated diffusion coefficients show interesting dependence on MC and distance from the evaporation surface. The advantage of using the methods presented is that the diffusion coefficient is calculated on a local level without having to define a function for the diffusion coefficient's dependency on other parameters

  • 6.
    Danvind, Jonas
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Eriksson, John
    Johansson, Håkan
    Calibration of a constitutive model for diffuse moisture transport in wood using data from X-ray CT-scanning and digital speckle photography2004Conference paper (Refereed)
  • 7. Danvind, Jonas
    et al.
    Morén, Tom
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Using X-ray CT scanning for moisture and displacement measurements in knots and their surroundings2004Conference paper (Refereed)
  • 8.
    Danvind, Jonas
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Synnergren, Per
    Method for measuring the shrinkage behaviour of drying woods using digital speckle photography and x-ray computerised tomography2001In: Moisture control in environment-friendly housing and wood drying technology in new century: July 9-13, 2001 Tsukuba, Japan / [ed] K. Hayashi, Ibaraki: Forestry and Forest Products Research Institute , 2001, p. 276-281Conference paper (Refereed)
  • 9. Eriksson, John
    et al.
    Johansson, Håkan
    Danvind, Jonas
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    A mass-transport model for drying wood under isothermal conditions2005In: Proceedings: 9th International IUFRO Wood Drying Conference, Nanjing Forestry University , 2005Conference paper (Refereed)
  • 10.
    Eriksson, John
    et al.
    Chalmers University of Technology.
    Johansson, Håkan
    Danvind, Jonas
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Numerical determination of diffusion coefficients in wood using data from CT-scanning2006In: Wood and Fiber Science, ISSN 0735-6161, Vol. 38, no 2, p. 334-344Article in journal (Refereed)
    Abstract [en]

    The radial moisture diffusion coefficient in Fick's law for a sample of Norway spruce (Picea abies) under isothermal drying conditions was determined in a parameterization of Arrhenius' equation type. Using X-ray CT-scanning, the wood density and moisture content distributions were obtained in the radial direction for the wood sample. An optimization scheme, based on finite element computation, was then applied to find the parameter values such that the difference between observed and computed moisture content was minimized. The combined numerical and experimental technique was developed to reduce known disadvantages of similar approaches, and a specific algorithm to determine diffusion coefficients was presented. A comparison of the calibrated diffusion coefficient with those given in the literature showed a good fit. The computed moisture content based on the obtained diffusion coefficient and the observed moisture content agreed well. Finally, the effect of measurement errors on the computed material parameter was found to be small

  • 11. Larsson, R.
    et al.
    Danvind, Jonas
    Imbaud, O.
    Morén, Tom
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Prediction modelling of colour changes on boards of Norway Spruce and Scots Pine during low temperature drying2005In: Proceedings: 9th International IUFRO Wood Drying Conference, Nanjing Forestry University , 2005Conference paper (Refereed)
  • 12. Larsson, Robert
    et al.
    Morén, Tom
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Danvind, Jonas
    Styrsystem för ändamålsstyrd torkning: förutsättningar och industriförsök2002Report (Other academic)
    Abstract [sv]

    Del A: Inledningsvis behandlas allmänna principer för adaptiv reglering av torkprocessen vad gäller solitt trä. De grundläggande meknaismerna som ligger bakom fukttransporten i trä vid artificiell torkning beskrivs även. På basis av denna fundamentala kunskap kan exempelvis parameterstyrning utvecklas för industriella satstorksystem. Ett antal principer för sådan styrning har implementerats i en laboratorietork. Del B: Ett antal industriförsök i full skala har genomförts för att undersöka hur en dynamisk återkoppling i styrsystemet kan ske. Exempelvis finns tydliga samband mellan vireksstapelns krympning och dess medelfuktkvot, vilket tillsammans med andra signaler från torkningen kan ge återkoppling i styrsystemet. En multivariat ansats kan vara en möjlig utveckling till ett styrsystem som även innefattar ett integrerat expertsystem för färgstyrning bl a.

  • 13. Scheepers, G.
    et al.
    Danvind, Jonas
    Morén, Tom
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Rypstra, T.
    An investigation of fluid water movement in birch during drying through variation of wood sap surface tension and initial average moisture2005In: Proceedings: 9th International IUFRO Wood Drying Conference, Nanjing Forestry University , 2005Conference paper (Refereed)
1 - 13 of 13
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf