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  • 1.
    Antti, Lena
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Heating and drying wood using microwave power1999Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The potentials for moisture flux in wood during microwave heating have been investigated experimentally and theoretically. The experiments were performed in three different kinds of microwave applicators. A computer model based on the finite difference method was developed to describe and predict the heat and mass transfer. The main conclusions are that microwave energy of 2.45 GHz frequency makes it possible to heat and dry pine and spruce 20 - 30 times faster than with conventional methods without any deterioration in drying quality. Some hardwoods are dried in approximately half the time compared to the softwoods. The drying method evokes unique results either with diminishing colour changes or with possibilities to create such during drying. However, to avoid unevenness in the electromagnetic field distribution and considering the limitation in power penetration depth the drying should be performed on line where wood components continuously are fed through a microwave field.

  • 2.
    Antti, Lena
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Microwave drying of hardwood: moisture measurements using CT-scanning1992In: Understanding the wood drying process: a synthesis of theory and practice : [proceedings of the] 3rd IUFRO conference on wood drying, August 18-21, 1992, Vienna, Austria, Wien: IUFRO , 1992Conference paper (Refereed)
  • 3.
    Antti, Lena
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Microwave drying of hardwood: potentials for moisture flux1993Licentiate thesis, monograph (Other academic)
  • 4.
    Antti, Lena
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Microwave drying of hardwood: Potentials for moisture flux1993In: Microwave and high frequency 1993: International congress : Papers, abstracts and programme., Göteborg: Institut für Volksmusikforschung und Ethnomusikologie, Universität für Musik und darstellende Kunst Wien, 1993, p. E2-Conference paper (Other academic)
  • 5.
    Antti, Lena
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Microwave drying of hardwood: simultaneous measurements of pressure, temperature, and weight reduction1992In: Forest products journal, ISSN 0015-7473, Vol. 42, no 6, p. 49-54Article in journal (Refereed)
  • 6.
    Antti, Lena
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Microwave drying of pine and spruce1995In: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 53, no 5, p. 333-338Article in journal (Refereed)
    Abstract [en]

    microwave energy consumption from 365 to 760 kWh/m 3. Internal wood temperatures up to 140°C were used. Internal vapour pressure in the wood could rise to about 20 kPa without checking. Maximal drying rates of 0.20 to 0.45% moisture content per minute are possible to obtain when drying above fiber saturation (fsp). Below fsp the feasible drying rates ranged from 0.10 to 0.20% moisture content per minute. Spruce dried approximately 1.6 times faster than pine. No conditioning of the wood was necessary since the wood was free of stresses. The wood was free of checks but colour changes occured in the interior of some specimens.

  • 7.
    Antti, Lena
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Några inverkande faktorer vid mikrovågstorkning av lövträ1991Report (Other academic)
  • 8.
    Antti, Lena
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Värmeövergång mellan trä och luft vid luftcirkulationstorkning: Klimat- och materialparametrars inverkan på värmeövergångstalet vid torkning av furu1989Report (Other academic)
  • 9.
    Antti, Lena
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Finell, M.
    Arshadi, M.
    Lestander, T.
    Microwave drying of sawdust: effect on biofuel pellet2010In: Proceedings, 11th International IUFRO Wood Drying Conference: in Skellefteå, Sweden, January 18 - 22, 2010 ... the theme of the conference was "Recent Advances in the Field of Wood Drying" / [ed] Tom Morén; Lena Antti; Margot Sehlstedt-Persson, Luleå: Luleå tekniska universitet, 2010, p. 313-319Conference paper (Refereed)
  • 10.
    Antti, Lena
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Finell, Michael
    Swedish University of Agricultural Sciences.
    Arshadi, Mehrdad
    Swedish University of Agricultural Sciences.
    Lestander, Torbjörn A.
    Swedish University of Agricultural Sciences.
    Effects of microwave drying on biomass fatty acid composition and fuel pellet quality2011In: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280, Vol. 6, no 1-2, p. 34-40Article in journal (Refereed)
  • 11.
    Antti, Lena
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Hansson, Lars
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Equalization of moisture in pre-dried pinewood using microwave power2010In: Pro Ligno, ISSN 1841-4737, E-ISSN 2069-7430, Vol. 6, no 2, p. 53-59Article in journal (Refereed)
    Abstract [en]

    Commonly, during air-circulation kiln drying moisture gradients within wood cross-sections are developed, i.e. the surfaces become drier than the interior. To minimize these gradients a conditioning step subsequent to the drying is needed. The aim with this study was to investigate the possibility to use microwave power for equalization of moisture within pinewood boards after air-circulation kiln drying to the average moisture content 0,14. Two dimensions of pinewood were tested; thickness 50 and 63 mm, in two different plants, generating 5 and 12 kW microwave power respectively. Results show that microwave energy give rise to a fast and advantageous moisture equalization within the wood. The higher microwave power density the faster heating and moisture redistribution in these wood dimensions. Required time for heating and redistribution of moisture was found to be as short as 3 minutes at the power density 500 kW/m3. In addition, split-tests indicate decreased or elimination of gap after microwave treatment in the investigated specimens.

  • 12.
    Antti, Lena
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Hansson, Lars
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Microwave treatment of resinous wood2006In: Wood structure and properties '06: [proceedings of the 5th IUFRO Symposium Wood Structure and Properties '06 held on September 3-6, 2006 in Sliač - Sielnica, Slovakia] / [ed] R. Lagana; S. Kurjatko; J. Kudela, Zvolen, Slovakia: Arbora Publishers , 2006, p. 435-437Conference paper (Refereed)
    Abstract [en]

    The output from conventional air-circulation drying of wood is not always satisfying; some individual wood boards often contain somewhat higher moisture content (MC) than the target MC. Higher MC in some pine wood boards after conventional drying could origin from the fact that these contain higher amounts of resin, which may delay or to some extent prevent the moisture flux. It could be the reason to problems in further wood production processes, as for example in gluing processes. The aim of this study was to determine whether or not microwave (MW) heating could be a suitable method to condition these components. Another aim was to investigate if and how migration of resin appears during MW treatment. The study includes experimental tests where determination of both MC and resin content (RC) were carried out before and after MW treatment. Results from the tests show that the RC and the MC are interacting; it means that volumes with high RC also withhold increased amount of moisture; these volumes are often found within boards that origin from the root end of logs. It is possible to dry/condition these planks to reach the target MC within minutes or hours, depending on wood thickness, using MW power. By exposing resinous wood to microwaves, migration of resin takes place from the interior towards the wood surfaces, especially longitudinally through the wood towards the butt ends. It seems to be possible to redistribute RC and MC in wood by exposing only parts of a plank to microwaves.

  • 13.
    Antti, Lena
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Hansson, Lars
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Redistribution of moisture in pre-dried pinewood using microwave power: a preliminary study2010In: Proceedings, 11th International IUFRO Wood Drying Conference: [... in Skellefteå, Sweden, January 18 - 22, 2010 ... the theme of the conference was "Recent Advances in the Field of Wood Drying"] / [ed] Tom Morén; Lena Antti; Margot Sehlstedt-Persson, Luleå: Luleå tekniska universitet, 2010, p. 234-238Conference paper (Refereed)
    Abstract [en]

    Commonly, during air-circulation kiln drying moisture gradients within wood cross-sections are developed, i.e. thesurfaces become drier than the interior. To minimize these gradients a conditioning step subsequent to the drying isneeded. The aim with this study was to investigate the possibility to use microwave power for redistribution ofmoisture within pinewood planks after air-circulation kiln drying to the average moisture content 0,14. Twodimensions of pinewood were tested; thickness 50 and 63 mm, in two different plants, generating 5 and 12 kWmicrowave power respectively. Results show that microwave energy give rise to a fast and advantageous moistureredistribution i.e. equalization of moisture content within the wood. The higher microwave power density the fasterheating and moisture equalization in these wood dimensions. Required time for heating and redistribution ofmoisture was found to be as short as 3 minutes at the power density 500 kW/m3. In addition, split-tests indicatedecreased or almost no gap in the investigated specimens.

  • 14.
    Antti, Lena
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Jönsson, Anette
    LTU.
    Nilsson, Magnus
    LTU.
    The effect of drying method on the mechanical properties of wood: Comparisons between conventional kiln and microwave dried Scots pine2001In: Proceedings of the 3rd European Cost E15 Workshop on Wood Drying: with the theme Softwood drying to meets needs of further processing and specific end-uses : 11-13 June 2001 at Scandic Hotel Kalastajatorppa, Helsinki, Finland, Espoo: VTT Building and Transport , 2001, p. 21:1-21:9Conference paper (Refereed)
  • 15.
    Antti, Lena
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Perre, P.
    ENGREF - Laboratory of Forest Sciences.
    A microwave applicator for on line wood drying: Temperature and moisture distribution in wood1999In: Wood Science and Technology, ISSN 0043-7719, E-ISSN 1432-5225, Vol. 33, no 2, p. 123-138Article in journal (Refereed)
    Abstract [en]

    An especially designed open microwave applicator was analysed using wood as the material to be heated and dried. The idea was to develop an on line microwave construction consisting of several small open applicators, each fed by a small standard magnetron (for example 1.4 kW main power). The process was analysed by measuring the wood temperature during heating using an IR-camera and detecting the moisture distribution during drying by CT-scanning. Pine and birch wood samples were used in the experiments, mainly 40 mm in thickness. The experiments show that the power distribution differs between dry wood and moist wood. The analysis of the temperature fields captured by the IR-camera during the first minutes allows a rather accurate determination of the MW power. Consequently, the drying proceeds unevenly in the wood specimens, especially in the longitudinal direction. The dimensions of the applicator and its relation to the wood dimension are very important. However, the wood was not destroyed, the temperature and moisture gradients did not affect the wood in terms of checks or deformations. The drying rate in different positions of the specimen varied between 0.30 and 0.80 percentage moisture content/min. The uneven energy, meaning temperature and field distribution, is to be compensated in the future by a moving wood load and by alternating the position of each applicator in a larger scale microwave pilot plant.

  • 16.
    Antti, Lena
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Torgovnikov, Grigori
    Microwave heating of wood1995In: Fifth international conference on microwave and high frequency heating, 17-21 September 1995, Cambridge: Cambridge University Press, 1995, p. E3.1-3.4Conference paper (Refereed)
  • 17.
    Antti, Lena
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Zhao, H.
    Turner, I.
    An Investigation of the Heating of Wood in an Industrial Microwave Applicator: Theory and Practice2000In: 6th international IUFRO wood drying conference on wood drying research and technology for sustainable forestry beyond 2000, Marcel Dekker Incorporated , 2000Conference paper (Refereed)
  • 18.
    Antti, Lena
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Zhao, H.
    Turner, I.
    Investigation of the heating of wood in an industrial microwave applicator: theory and practice2000In: Drying Technology, ISSN 0737-3937, E-ISSN 1532-2300, Vol. 18, no 8, p. 1665-1676Article in journal (Refereed)
    Abstract [en]

    In this work a comprehensive set of experimental results are used as an excellent means to understand the coupling that exists between the material and the electromagnetic fields in a specific industrial microwave applicator. The analysis of the infrared images allows an accurate map of the power and temperature distributions within the wood sample to be determined. This map, together with the simulation results of a previously developed computational electromagnetic model, can provide a detailed understanding of the design features of the microwave applicator. In particular, it is possible to locate the occurrence of localised hot spots and to examine the uniformity of the heat distribution throughout the sample. The simulation results provide the evolution of the electromagnetic fields inside the entire applicator and the sample. The coupling of theory and practice is the best way to proceed in optimising the design and for proposing new applicator geometry that can heat the material more effectively.

  • 19.
    Hansson, Lars
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Antti, Lena
    Design and performance of an industrial microwave drier for on-line drying of wood components2003In: Proceedings of the 8th IUFRO International Wood Drying Conference: Improvement and innovation in wood drying : a major issue for a renewable material : 24-29 August 2003, Brasov, Romania / [ed] Mihai Ispas; Sergiu T Chiriacescu, Brasov: Transilvania University of Brasov, Faculty of Wood Industry , 2003, p. 156-158Conference paper (Other academic)
    Abstract [en]

    The most common industrial method for drying wood is by air circulation. However, an alternative method - microwave drying-has been investigated at the Division of Wood Physics, Luleå University of Technology in Skellefteå, Sweden. The use of microwave energy to dry wood is not very common, but it could be advantageous due to the possibility of heating and drying wood much faster than conventional methods and with preserved quality. The objective of the investigation is to install an on-line microwave drier for wood components and, furthermore, to integrate this drying process into the total production. The purpose of this paper is to briefly describe the design and performance of this on-line microwave drier, its advantages and its limitations.

  • 20.
    Hansson, Lars
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Antti, Lena
    Modeling microwave heating and moisture redistribution in wood2008In: Drying Technology, ISSN 0737-3937, E-ISSN 1532-2300, Vol. 26, no 5, p. 552-559Article in journal (Refereed)
    Abstract [en]

    A finite element model was developed to describe and explain microwave heating of wood and the following moisture redistribution in wood. Dielectric and thermal properties are of great importance, since they are continuously affected during the process by moisture content, density, grain direction, temperature, and more. Computer tomography was used to detect wood density and moisture content. Heat distribution was verified by fiber-optic temperature sensors. The tests were performed in a designed microwave dryer based on 1-kW generators, 2.45GHz. The results show that finite element modeling is a powerful tool to simulate heat and mass transfer in wood, providing the material is well described.

  • 21.
    Hansson, Lars
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Antti, Lena
    The effect of drying method and temperature level on the hardness of wood2006In: Journal of Materials Processing Technology, ISSN 0924-0136, E-ISSN 1873-4774, Vol. 171, no 3, p. 467-470Article in journal (Refereed)
    Abstract [en]

    The purpose of the present work was to investigate whether wood hardness is affected by temperature level during microwave (MW) drying and whether the response is different from that of conventionally dried wood. Matched samples of Norway spruce (Picea abies) were therefore dried from green state to different moisture content (mc) at different temperature levels, both conventionally by air circulation and by MW. The results show that specimens dried by any of the two methods at a temperature level of 100 or 60°C there is a significant difference in wood hardness parallel to the grain between the methods when drying progresses to relatively lower level of moisture content, i.e. wood hardness becomes higher during MW drying. Temperature level in the range 60-110°C during MW drying has no significant influence on wood hardness. Variables such as density and mc have a greater influence on wood hardness than does the drying method or the drying temperature. Since wood is a biological material, its strength varies within the specimens as well as between different samples. For this reason it is important to use matched samples when performing this type of comparative investigation.

  • 22.
    Hansson, Lars
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Antti, Lena
    The effect of microwave drying on Norway spruce woods strength: a comparison with conventional drying2003In: Journal of Materials Processing Technology, ISSN 0924-0136, E-ISSN 1873-4774, Vol. 141, no 1, p. 41-50Article in journal (Refereed)
    Abstract [en]

    The purpose of the present work was to investigate whether the drying method itself affects strength of wood apart from fibre direction, density, temperature in the wood, moisture content and with which angle the microfibril is placed in the middle layer at the secondary cell wall S2. The drying methods compared were microwave drying and conventional air-circulation drying, and the species tested was Norway spruce. The result shows that it is not possible to demonstrate any difference between the two drying methods with respect to the strength of the wood. What affects wood strength are such variables as moisture content, number of annual rings and the density properties weight, width and thickness

  • 23.
    Hansson, Lars
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Antti, Lena
    Lundgren, Nils
    Hagman, Olle
    Finite element modeling (FEM) simulation of interactions between wood and microwaves2006In: Journal of Wood Science, ISSN 1435-0211, E-ISSN 1611-4663, Vol. 52, no 5, p. 406-410Article in journal (Refereed)
    Abstract [en]

    The aim of this study was to use finite element modeling (FEM) as a tool to analyze microwave scattering in wood and to verify the model by measurements with a microwave scanner. A medical computed tomography scanner was used to measure distribution of density and moisture content in a piece of Scots pine (Pinus sylvestris). Dielectric properties were calculated from measured values for cross sections from the piece and used in the model. Images describing the distribution of the electric field and phase shift were obtained from the FEM simulation. The model was verified by measurements with a scanner based on a microwave sensor. The results show that simulated values correspond well to measured values. Furthermore, discontinuities in the material caused scattering in both the measured and the simulated values. The greater the discontinuity in the material, the greater was the need for computational power in the simulation.

  • 24.
    Hansson, Lars
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Antti, Lena
    Morén, Tom
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    IR- och HFV-teknik för virkestorkning2002Report (Other academic)
    Abstract [sv]

    Syftet med föreliggande arbete är att presentera några relativt nya virkestorkningsmetoder. Tanken är att visa på metodernas möjligheter och begränsningar för den svenska träbranschen. De metoder som valts ut är torkning med hjälp av infraröd strålning och högfrekvens/vakuum-torkning. Studien baseras på fysikaliska förutsättningar, litteraturinventering, intervjuer med metodutvecklare och i IR-fallet på medverkan vid praktiska kvalitetsmätningar av det torkade virket. Resultatet visar att teknologin som bygger på infraröd teknik möjligen kan minska torkningstiden, men detta antagande bygger endast på den grundläggande fysiken bakom teknologin. De som har investerat i denna teknologi vill ej ge ut information kring tekniken innan den grundligt har testats. Därför finns en del obesvarade frågeställningar, såsom hur mycket tid som kan tjänas vid torkningen, energiåtgångens storlek samt vilken torkningskvalitet som erhålls med denna torkningsmetod. Det sistnämnda undersöks för närvarande av Trätek. Högfrekvens/vakuumtekniken som beskrivs här är utvecklad i Kanada och används industriellt där, än så länge dock i liten skala. Träslag som på senare tid undersökts och torkas med denna metod är företrädesvis nordamerikanskt barrvirke. Metoden lämpar sig ur ekonomiskt perspektiv (i Kanada) framför allt för torkning av grövre dimensioner, men också för att fuktutjämna konventionellt torkat virke. Fördelarna med metoden jämfört med konventionell teknik är kortare torkningstid, mindre förekomst av ytsprickor, inre spänningar och fläckvis missfärgning förekommer inte alls och dessutom uppnås en jämn slutfuktkvot i hela lasten. Virket behöver inte ströläggas då den huvudsakliga fukttransporten sker i fiberriktningen. Svårigheter med torkstyrningen i form av övertorkning och kollaps har numera minimerats genom den senaste generationen högfrekvens-/vakuumtorkar. Metoden kräver tillgång till elenergi och energiförbrukningen uppges till 1.2 kWh per kg bortfört vatten.

  • 25.
    Hansson, Lars
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Lundgren, Nils
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Antti, Lena
    Hagman, Olle
    FEM simulation of heating wood in an industrial microwave applicator2005In: 10th International Conference on Microwave and High Frequency Heating : Modena, Italy, September 12 - 15, 2005 / [ed] Cristina Leonelli, 2005Conference paper (Refereed)
  • 26.
    Hansson, Lars
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Lundgren, Nils
    Antti, Lena
    Hagman, Olle
    Microwave penetration in wood using imaging sensor2005In: Measurement, ISSN 0263-2241, E-ISSN 1873-412X, Vol. 38, no 1, p. 15-20Article in journal (Refereed)
    Abstract [en]

    It is possible to determine properties of wood using microwave scanning techniques. The purpose of this study was to verify the measured values from a microwave imaging sensor. Attenuation and phase shift of an electromagnetic wave transmitted through birch wood were measured and compared with theoretical calculated values. A test piece with varying thickness was measured with a scanner based on a microwave sensor (Satimo 9.375GHz) at different temperatures and moisture contents. The density distribution of the test piece was determined by computer tomography scanning. The result showed good correspondence between measured and theoretical values. The proportion of noise was higher at low moisture content due to lower attenuation. There is more noise in attenuation measurement than in measurement of phase shift. A reason for this could be that wood is an inhomogeneous material in which reflections and scattering affect attenuation more than phase shift. The microwave scanner has to be calibrated to a known dielectric to quantify the error in the measurement

  • 27. Lundgren, Nils
    et al.
    Hansson, Lars
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Hagman, Olle
    Antti, Lena
    FEM simulation of interactions between microwaves and wood during thawing2006In: Mathematical modeling of wave phenomena: conference on mathematical modeling of wave phenomea, Växjö, Sweden, 14 - 19 August 2005 / [ed] Börje Nilsson; Louis Fishman, Melville, NY: American Institute of Physics (AIP), 2006, p. 260-267Conference paper (Refereed)
    Abstract [en]

    Dipole polarization of water molecules is an important factor when microwaves interact with moist wood. Hence there will be a considerable change in dielectric properties when the wood changes from frozen to nonfrozen condition. The aim of this study was to develop a model that simulates measurements with a microwave scanner based on a sensor working at 9.4 GHz. Two-dimensional finite element modelling (FEM) was implemented to analyze interactions between microwaves and green wood during thawing of frozen wood at room temperature. A medical computed tomography scanner was used to measure the internal structure of density in a piece of wood in green and dry condition. From these density images the distribution of dry weight moisture content was calculated for a cross section of the piece and used in the model. Images describing the distribution of the electric field and phase shift at different temperatures where obtained from the FEM simulation. The results show that simulated values correspond well to measured values. This confirms that the model presented in this study is a useful tool to describe the interaction between microwaves and wood during microwave scanning at varying conditions.

  • 28.
    Vikberg, Tommy
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Oja, Johan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Antti, Lena
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Moisture content measurement in Scots pine by microwave and X-rays2012In: Wood and Fiber Science, ISSN 0735-6161, Vol. 44, no 3, p. 280-285Article in journal (Refereed)
    Abstract [en]

    There is demand in the Swedish sawmill industry to improve the accuracy of moisture content measurements, both to obtain a better tool to run production and to ensure that the products meet customer expectations. In this study, 240 well-conditioned pieces of Scots pine (Pinus sylvestris), sorted into five different groups by visual inspection, were measured using microwaves and X-rays. Models to predict moisture content of wood were made by measurements of an additional 45 pieces of wood. Using only measured quantities from the microwave system, ie attenuation and phase shift, the root mean square error (RMSE) of the estimated moisture content was 1.00%. By adding total density from the X-ray measurements, RMSE of the estimated moisture content was lowered to 0.89%. Mean errors of the different wood groups varied from -0.65 to 0.18%.

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