| 1. |
- Johansson, Carl-Johan, et al.
(författare)
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Sågverksnytt nr 1
- 2013
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Rapport (övrigt vetenskapligt/konstnärligt)
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| 2. |
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| 3. |
- Hu, Min, et al.
(författare)
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Local variation of modulus of elasticity in timber determined on the basis of non-contact deformation measurement and scanned fibre orientation
- 2014
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Ingår i: European Journal of Wood and Wood Products. - : Springer Science and Business Media LLC. - 0018-3768 .- 1436-736X. ; 73:1, s. 17-27
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Tidskriftsartikel (refereegranskat)abstract
- During the last decade, the utilization of non-contact deformation measurement systems based on digital image correlation (DIC) has increased in wood related research. By measuring deformations with DIC systems, surface strain fields can be calculated. The first aim of this study concerns the possibility to detect detailed strain fields along the entire length of a wooden board subjected to pure bending and the potential of using such strain fields to determine a bending modulus of elasticity (MOE) profile along a board. Displacements were measured over 12 subareas along a flat surface of the board. For each such area, a separate local coordinate system was defined. After the transformation of locally measured coordinates to a global system, high resolution strain fields and a corresponding bending MOE profile were calculated. A second method in establishing bending MOE profiles is to use fibre angle information obtained from laser scanning and a calculation model based on integration of bending stiffness over board cross sections. Such profiles have recently been utilized for accurate strength grading. A second aim of this study was to investigate the accuracy of the bending MOE profiles determined using the latter method involving fibre angle information. Bending MOE profiles determined using the two described methods agree rather well. However, for some patterns of knot clusters, the local bending MOE, calculated on the basis of fibre angles and integration of bending stiffness, is overestimated. Hence, this research adds knowledge that may be utilized to improve the newly suggested strength grading method.
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| 4. |
- Jarlemark, Per, et al.
(författare)
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Measurement accuracy in Network-RTK
- 2010
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Ingår i: Bolletino di Geodesia e Scienze Affini. ; 69, s. 2-3
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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| 5. |
- Johansson, Dongni, 1988, et al.
(författare)
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Tonic-clonic seizure detection using accelerometry-based wearable sensors: A prospective, video-EEG controlled study
- 2019
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Ingår i: Seizure : the journal of the British Epilepsy Association. - : Elsevier BV. - 1059-1311 .- 1532-2688. ; 65, s. 48-54
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Tidskriftsartikel (refereegranskat)abstract
- Purpose: The aim of this prospective, video-electroencephalography (video-EEG) controlled study was to evaluate the performance of an accelerometry-based wearable system to detect tonic-clonic seizures (TCSs) and to investigate the accuracy of different seizure detection algorithms using separate training and test data sets. Methods: Seventy-five epilepsy surgery candidates undergoing video-EEG monitoring were included. The patients wore one three-axis accelerometer on each wrist during video-EEG. The accelerometer data was band-pass filtered and reduced using a movement threshold and mapped to a time-frequency feature space representation. Algorithms based on standard binary classifiers combined with a TCS specific event detection layer were developed and trained using the training set. Their performance was evaluated in terms of sensitivity and false positive (FP) rate using the test set. Results: Thirty-seven available TCSs in 11 patients were recorded and the data was divided into disjoint training (27 TCSs, three patients) and test (10 TCSs, eight patients) data sets. The classification algorithms evaluated were K-nearest-neighbors (KNN), random forest (RF) and a linear kernel support vector machine (SVM). For the TCSs detection performance of the three algorithms in the test set, the highest sensitivity was obtained for KNN (100% sensitivity, 0.05 FP/h) and the lowest FP rate was obtained for RF (90% sensitivity, 0.01 FP/h). Conclusions: The low FP rate enhances the clinical utility of the detection system for long-term reliable seizure monitoring. It also allows a possible implementation of an automated TCS detection in free-living environment, which could contribute to ascertain seizure frequency and thereby better seizure management.
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| 6. |
- Karlsson, Stefan, 1984-, et al.
(författare)
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The effect of single-side ion exchange on the flexural strength of plain float glass and float glass containing a drilled hole
- 2013
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Ingår i: Glass Technology. - 0017-1050. ; 54:2, s. 66-71
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Tidskriftsartikel (refereegranskat)abstract
- The effect of single-side ion exchange (using a KNO3:KCl mixture) on the ring-on-ring flexural strength of float glass has been studied. Two ion exchanged series, treated at 450 and 515°C, were investigated. The ion exchanged samples showed approximately 160 respectively 100% increases in their arithmetic mean strength compared to as-received float glass. Furthermore, a series of samples containing drilled holes were studied in order to investigate the effect of singleside ion exchange on such common construction elements. The samples that contained drilled holes were ion exchanged at 450°C and showed around 140% increase of the fracture load compared to the untreated samples containing drilled holes. As a general observation, the ion exchange treatment induced ∼110 MPa compressive stresses (515°C) and ∼180 MPa compressive stresses (450°C). The ion exchanged samples showed no significant increase in stiffness.
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| 7. |
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| 8. |
- Nyman, Bertil, et al.
(författare)
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Sprickor i golv
- 2010
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Ingår i: CBI nytt. - 0349-2060. ; :1, s. 10-
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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| 9. |
- Olsson, Anders, 1973-, et al.
(författare)
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Prediction of timber bending strength and in-member cross-sectional stiffness vartiation on basis of local wood fibre orientation
- 2013
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Ingår i: European Journal of Wood and Wood Products. - : Springer. - 0018-3768 .- 1436-736X. ; 71:3, s. 319-333
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Tidskriftsartikel (refereegranskat)abstract
- Machine strength grading of structural timber is based upon relationships between so called indicating properties (IPs) and bending strength. However, such relationships applied on the market today are rather poor. In this paper, new IPs and a new grading method resulting in more precise strength predictions are presented. The local fibre orientation on face and edge surfaces of wooden boards was identified using high resolution laser scanning. In combination with knowledge regarding basic wood material properties for each investigated board, the grain angle information enabled a calculation of the variation of the local MOE in the longitudinal direction of the boards. By integration over cross-sections along the board, an edgewise bending stiffness profile and a longitudinal stiffness profile, respectively, were calculated. A new IP was defined as the lowest bending stiffness determined along the board. For a sample of 105 boards of Norway spruce of dimension 45 × 145 × 3600 mm, a coefficient of determination as high as 0.68-0.71 was achieved between this new IP and bending strength. For the same sample, the coefficient of determination between global MOE, based on the first longitudinal resonance frequency and the board density, and strength was only 0.59. Furthermore, it is shown that improved accuracy when determining the stiffness profiles of boards will lead to even better predictions of bending strength. The results thus motivate both an industrial implementation of the suggested method and further research aiming at more accurately determined board stiffness profiles.
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| 10. |
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