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- Hyll, Kari, et al.
(författare)
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CT-skanning som verktyg för detektering av törskateangrepp på tall
- 2022
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Rapport (refereegranskat)abstract
- Scots pine blister rust fungi (Cronartium pini) is expected to become an increasing problem for both forest owners and sawmills in the Nordic region, and there is great uncertainty about the economic consequences. There is also a lack of knowledge about the biology of Scots pine blister rust, as well as the tree's response and defence against ongoing infection. The tree is known to defend itself by enriching resin at the infected area, creating a damaged area of resin-wood. There is currently no reliable way to detect and assess the degree of damage in sawn timber, which leads to waste, as entire sawlogs are usually downgraded when parts or most of the timber could possibly be used. The objectives of this preliminary study were to: (1) investigate whether X-ray computed tomography (CT scanning) can detect blister rust damage in pine timber, in order to optimise sawing and save the value of the sawn timber; (2) to compare the 3-dimensional CT image description of the fungal attack with how the damage looks on the outside, to enable recommendations for external assessment of the damage attack, for example during felling; and (3) to assess the possibilities for describing the course of the damage and the tree's defence against the fungal attack.Eight rust-infested and two non-infested trees (Scots pine) were collected from a thinning stand and a mature stand outside Bjurselet, Norsjö municipality in Västerbotten. The trees were felled in January 2022. After felling, the stems were visually inspected, and infected parts were marked with paint on the mantle surface. The stems were cut into logs of suitable length for transport and scanning. Cuts through fungal-infested regions were avoided. The wood was transported to LTU’s Wood Science and Engineering facility in Skellefteå for CT scanning.The CT scan of the sample trees showed that damage due to pine blister rust can be detected in a way that enables further development of an industrial detection method and optimisation of the wood decomposition. However, one difficulty discovered was that fungal-infested sapwood areas have similar image intensity as non-infested heartwood. It could also be established that the distribution of damage inside the volume of the stem is greater than can be detected visually on the mantle, especially in the longitudinal direction. In this study the temporal development of the infection from the time of infestation to the time of CT scanning could not be analysed. However, annual rings could be distinguished in both damaged and undamaged wood, making it possible to monitor the evolution of the damage from year to year. DNA analysis detected the presence of blister rust fungus in the wood, both in and outside resin-rich areas. The highest amount of fungus-specific DNA was measured outside the resin-rich area in the outer parts of the sapwood.
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- Hyll, Kari, 1984-
(författare)
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Image-based quantitative infrared analysis and microparticle characterisation for pulp and paper applications
- 2016
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Measurements of process variations and particle morphology are widely employed in the pulp and paper industry. Two techniques with high potential, infrared thermography and microparticle characterisation, are mainly used qualitatively. Quantitative thermography requires knowledge of the emittance, a material property which has not been measured under many process-relevant conditions. Quantitative characterisation of microparticles, e.g. pulp fines and mineral fillers, requires the analysis of a large number of particles, which can be accomplished using flow microscopes. Flow microscopes for pulp analysis have had insufficient spatial resolution to resolve fines and fillers. Additionally, there has been a lack of methods which can differentiate between fines and fillers in a mixed suspension.State-of-the-art instruments for particle image analysis were evaluated and compared to laser diffractometry, a measurement method based on scattering by diffraction. Laser diffractometry was found to be highly sensitive to the complex refractive index of the particles, and especially to its change due to moisture absorption. A high-resolution imaging flow cytometer and a high-resolution fibre analyser were found to be complementary for characterisation of pure fines and fines/filler mixtures, and superior to laser diffractometry. A method for differentiating between fines and fillers in a suspension based on their autofluorescence and side-scattering was proposed and qualitatively evaluated.Furthermore, a method for measuring the directional and integrated emittance of paper was developed and its accuracy was determined. Measurements on a wide range of samples showed that the emittance of fibre-based materials vary significantly with wavelength, pulp type, observation angle, and moisture content. By applying measured quantitative values of the emittance, the thermal energy emitted by sack paper samples during mechanical deformation could be quantitatively calculated. The increase in thermal energy at the time of rupture was found to correlate well with the elastic share of the mechanical energy that was stored in the sample during its elongation.In summary, the results of this work have facilitated the use of quantitative microparticle analysis and infrared thermography for pulp and paper applications.
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- Kari, Hyll, 1984-, et al.
(författare)
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Characterization of morphological changes of chemical pulp fibres and fines due to refining
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- The influence of the refining process on the morphological changes of a chemical softwood pulp was investigated. An industrial-like laboratory refiner was used, where the pulp was refined with five refining segments with differences in bar widths, groove widths, and cutting angles. The refined pulp was characterized with a fibre analyser with a spatial resolution of approximately 4 µm/pixel and a wide size range. The fines fraction of the refined pulp was also characterized with an imaging flow cytometer with a spatial resolution of 0.33 µm/pixel and a narrower size range.The fibre analyser measurements showed that the mean length, width, and aspect ratio of the fines decreased monotonically with accumulated refining energy. The imaging flow cytometer with its higher spatial resolution showed little change in fines morphology with accumulated refining energy.The morphology of the fines was more dependent on the applied specific refining energy than the design of the refining segment. However, a segment with much finer grooves and bars, initially designed for hardwood, gave significantly less fibre shortening, fines generation, external fibrillation, kink, and fines that were more fibrillar, compared to the other segments.
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- Kari, Hyll, 1984-, et al.
(författare)
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Optical methods for fines and filler size characterization : Evaluation and comparison
- 2016
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The pulp fines and mineral fillers in the fine fraction of a papermaking stock influence process conditions and sheet properties. The influence is largely dependent on the size and shape of the particles. Quantitative characterization of the size and shape of fines and fillers would aid in process control and prediction of product properties. Thus, the aim of the study was to evaluate and compare optical instruments which can be used to quantitatively characterize the fine fraction of a papermaking stock. The compared instruments were the Mastersizer2000 from Malvern, based on diffraction scattering of a laser beam, the ImageStream from Amnis, and the Fiber Tester and Fiber Tester Plus from ABB Lorentzen & Wettre. The last three instruments are all based on imaging of the particles and have spatial resolutions ranging from 0.33 µm to about 10 µm per pixel.All instruments overestimated the size of calibration spheres with known sizes. In several cases, calibration particles that were smaller than the spatial resolution of the instrument were detected. In these cases, the relative measurement error was large, likely due to positioning and quantization errors. It is also suggested that the oversizing was partly due to dissimilar optical properties of the calibration particles, compared to the typical sample, and that better calibration materials for fines need to be developed.For the image-based instruments, the relative share of fines and filler particles increased with as the size of the measured particles decreased. Thus, with higher spatial resolution, more particles were detected. However, the shape of the particle size distribution depended on the resolution and the field-of-view. The ImageStream resolved single PCC particles, which has not previously been done using flow microscopy. Due to its limited field-of-view, the ImageStream could not measure the largest fines, which were detected by the Fiber Tester and Fiber Tester Plus. While the Fiber Tester Plus did not resolve single PCC particles, it detected, due to its higher resolution, a higher share of smaller particles than the Fiber Tester. Overall, the ImageStream and the Fiber Tester Plus were found to be complementary.The diffraction-based method struggled to measure small fines. It is proposed that small fines diffracted light insufficiently to be detected by the instrument. The obtained result was also highly sensitive to the choice of refractive index; a fact that some of the previous users apparently were not aware of.In summary, image-based methods were found to perform better than the diffraction-based method when measuring on fines and mixtures of fines and fillers, while the highest resolution image-based instrument and the diffraction-based method were best when measuring on pure fillers.
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