| 1. |
- Andersson, J, et al.
(författare)
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Ageing of Flexographic Printed Model Cellulose Surfaces and Determination of the Mechanisms Behind Ageing
- 2009
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Ingår i: Pulp & paper Canada. - 0316-4004. ; 110:6, s. 34-38
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Tidskriftsartikel (refereegranskat)abstract
- The influence of storage conditions on the ink detachment efficiency of water-based flexographic ink printed onto model cellulose surfaces and handsheets was investigated. It was shown that UV light, elevated temperatures, longer storage time, increasing surface roughness, and increasing surface hydrophobicity all had a negative effect on ink detachment. It was also shown that the ink's chemical and structural characteristics changed when stored at elevated temperatures. No chemical or structural changes could be observed for the ink when stored under UV light.
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| 2. |
- Andreasson, B., et al.
(författare)
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Determination of fibre pore structure : influence of salt, pH and conventional wet strength resins
- 2005
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Ingår i: Cellulose. - : Springer Science and Business Media LLC. - 0969-0239 .- 1572-882X. ; 12:3, s. 253-265
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Tidskriftsartikel (refereegranskat)abstract
- It has been shown, in the present investigation, that the two methods used to investigate the pore size distribution of unbleached chemical pulps, i.e. inverse size exclusion chromatography (ISEC) and nuclear magnetic resonance (NMR), give different average pore radius for the pores inside the fibre wall. This is due to the way in which these experiments are performed and the sensitivity of the methods to different types of pores in the cell wall. It was also shown that the two methods gave different results when changing the pH and the ionic strength of the pulp suspension. The pore radius, as detected with ISEC, decreased with both increasing ionic strength and decreasing pH, indicating a loose structure of the exterior of the fibrillar network. However, the pore radius as detected with NMR, was virtually unaffected when increasing the ionic strength, indicating a very rigid structure of the interior of the fibre wall. Decreasing pH though, lead to a decrease in pore radius indicating that upon protonation of the carboxylic groups in the fibre wall, the electrostatic repulsion is diminished and the average pore radius decreases. The NMR technique was also used to study wet strength aid penetration into the fibre wall. It was shown that wet strength aids with a small molecular weight, penetrated the fibre wall, as detected by a decrease in pore radius. It was also shown that addition of different wet strength aids increased the tensile index of the sheet and decreased the fibre strength, measured as zero span-strength of the sheets.
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| 3. |
- Badel, Xavier, et al.
(författare)
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Performance of scintillating waveguides for CCD-based X-ray detectors
- 2006
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Ingår i: IEEE Transactions on Nuclear Science. - 0018-9499 .- 1558-1578. ; 53:1, s. 3-8
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Tidskriftsartikel (refereegranskat)abstract
- Scintillating films are usually used to improve the sensitivity of CCD-based X-ray imaging detectors. For an optimal spatial resolution and detection efficiency, a tradeoff has to be made on the film thickness. However, these scintillating layers can also be structured to provide a pixellated screen. In this paper, the study of CsI(TI)-filled pore arrays is reported. The pores are first etched in silicon, then oxidized and finally filled with CsI(TI) to form scintillating waveguides. The dependence of the detector sensitivity on pore depth, varied from 40 to 400 mu m here, follows rather well theoretical predictions. Most of the detectors produced in this work have a detective quantum efficiency of the incoming X-ray photons of about 25%. However, one detector shows that higher efficiency can be achieved approaching almost the theoretical limit set by Poisson statistics of the incoming X-rays. Thus, we conclude that it is possible to fabricate scintillating waveguides with almost ideal performance. Imaging capabilities of the detectors are demonstrated.
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| 4. |
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| 5. |
- Bäckström, Marie, et al.
(författare)
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Beatability and runnability studies of ion-exchanged unbleached kraft pulps on a pilot scale
- 2009
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Ingår i: Nordic Pulp & Paper Research Journal. - : Walter de Gruyter GmbH. - 0283-2631 .- 2000-0669. ; 24:1, s. 94-100
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Tidskriftsartikel (refereegranskat)abstract
- It has earlier been shown that the counter-ion to the charged groups in the fibre has a significant effect on the beatability of fibres, but large-scale investigations of this effect are scarce in the literature. The objectives of the present study were therefore to develop a technique to ion-exchange large quantities of industrial pulp into the Na +-form using complexing agents and to study the effect of industrial-scale refining on pulp fibres in the Na +-form and how the fibres respond to industrial-like papermaking. The results show that ion-exchange can indeed be conducted on a pilot-scale using complexing agents such as DTPA. The study further indicates that an energy reduction of 50% at a given WRV or tensile index may be achieved if the fibres are converted to Na +-form prior to pilot-scale refining. By applying these techniques in full-scale production, it should thus be possible to save significant amount of energy, especially in the case of papers made from unbleached pulp that usually demands a higher degree of beating to achieve sufficient strength.
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| 6. |
- Castleton, Christopher, 1969-, et al.
(författare)
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Managing the supercell approximation for charged defects in semiconductors : Finite-size scaling, charge correction factors, the band-gap problem, and the ab initio dielectric constant
- 2006
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 73:035215, s. 11-
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Tidskriftsartikel (refereegranskat)abstract
- The errors arising in ab initio density functional theory studies of semiconductor point defects using the supercell approximation are analyzed. It is demonstrated that (a) the leading finite size errors are inverse linear and inverse cubic in the supercell size and (b) finite size scaling over a series of supercells gives reliable isolated charged defect formation energies to around +-0.05 eV. The scaled results are used to test three correction methods. The Makov-Payne method is insufficient, but combined with the scaling parameters yields an ab initio dielectric constant of 11.6+-4.1 for InP. Gamma point corrections for defect level dispersion are completely incorrect, even for shallow levels, but realigning the total potential in real-space between defect and bulk cells actually corrects the electrostatic defect-defect interaction errors as well. Isolated defect energies to +-0.1 eV are then obtained using a 64 atom supercell, though this does not improve for larger cells. Finally, finite size scaling of known dopant levels shows how to treat the band gap problem: in < or = 200 atom supercells with no corrections, continuing to consider levels into the theoretical conductin band (extended gap) comes closest to experiment. However, for larger cells or when supercell approximation errors are removed, a scissors scheme stretching the theoretical band gap onto the experimental one is in fact correct.
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| 7. |
- Danielson, Mats, et al.
(författare)
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Computing Upper and Lower Bounds in Interval Decision Trees
- 2007
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Ingår i: European Journal of Operational Research. - : Elsevier BV. - 0377-2217 .- 1872-6860. ; 181:2, s. 808-816
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Tidskriftsartikel (refereegranskat)abstract
- This article presents algorithms for computing optima in decision trees with imprecise probabilities and utilities. In tree models involving uncertainty expressed as intervals and/or relations, it is necessary for the evaluation to compute the upper and lower bounds of the expected values. Already in its simplest form, computing a maximum of expectancies leads to quadratic programming (QP) problems. Unfortunately, standard optimization methods based on QP (and BLP - bilinear programming) are too slow for the evaluation of decision trees in computer tools with interactive response times. Needless to say, the problems with computational complexity are even more emphasized in multi-linear programming (MLP) problems arising from multi-level decision trees. Since standard techniques are not particularly useful for these purposes, other, non-standard algorithms must be used. The algorithms presented here enable user interaction in decision tools and are equally applicable to all multi-linear programming problems sharing the same structure as a decision tree.
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| 8. |
- Danielson, Mats, et al.
(författare)
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Cross-Disciplinary Research in Analytic Decision Support Systems
- 2006
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Ingår i: ITI 2006. - Zagreb : University Computing Centre SRCE, University of Zagreb. - 9537138054 ; , s. 123-128
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Konferensbidrag (refereegranskat)abstract
- A main problem in decision support contexts is that unguided decision making is difficult and can lead to inefficient decision processes and undesired consequences. Therefore, decision support systems (DSSs) are of prime concern to any organization and there have been numerous approaches to delivering decision support from, e.g., computational, mathematical, financial, philosophical, psychological, and sociological angles. A key observation, however, is that effective and efficient decision making is not easily achieved by using methods from one discipline only. This paper describes some efforts made by the DECIDE Research Group to approach DSS development and decision making tools in a cross-disciplinary way.
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| 9. |
- Danielson, Mats, et al.
(författare)
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Distribution of expected utility in decision trees
- 2007
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Ingår i: International Journal of Approximate Reasoning. - : Elsevier BV. - 0888-613X .- 1873-4731. ; 46:2, s. 387-407
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Tidskriftsartikel (refereegranskat)abstract
- Evaluation of decision trees in which uncertain information is present is complicated. Especially when the tree has some depth, i.e. consists of more than one level, the effects of the choice of representation and evaluation procedures are significant. Second-order representation and evaluation may significantly increase a decisionmaker's understanding of a decision situation when handling aggregations of imprecise representations, as is the case in decision trees or influence diagrams, while the use of only first-order results gives an incomplete picture. Furthermore, due to the effects on the distribution of belief over the intervals of expected utilities, the Gamma-maximin decision rule seems to be unnecessarily pessimistic as the belief in neighbourhoods of points near interval boundaries is usually lower than in neighbourhoods near the centre. Due to this, a generalized expected utility is proposed. The results in this paper apply also to approaches which do not explicitly deal with second-order information, such as standard decision trees or probabilistic networks using only first-order concepts, for example upper and lower bounds. Furthermore, the results also apply to other, non-probabilistic weighted trees such as multi-criteria weight trees.
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| 10. |
- Ekenberg, Love, et al.
(författare)
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Distributions over Expected Utilities in Decision Analysis
- 2007
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Ingår i: ISIPTA 2007 - Proceedings of the 5th International Symposium on Imprecise Probability: Theories and Applications. - 9788086742205 ; , s. 175-182
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Konferensbidrag (refereegranskat)abstract
- It is often recognised that in real-life decision situations, classical utility theory puts too strong requirements on the decision-maker. Various interval approaches for decision making have therefore been developed and these have been reasonably successful. However, a problem that sometimes appears in real-life situations is that the result of an evaluation still has an uncertainty about which alternative is to prefer. This is due to expected utility overlaps rendering discrimination more difficult. In this article we discuss how adding second-order information may increase a decision-maker�s understanding of a decision situation when handling aggregations of imprecise representations, as is the case in decision trees or influence diagrams.
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