| 1. |
- 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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| 2. |
- 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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| 3. |
- 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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| 4. |
- Engqvist, Cecilia, et al.
(författare)
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Interactions between single latex particles and silica surfaces studied with AFM
- 2007
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Ingår i: Colloids and Surfaces A. - : Elsevier BV. - 0927-7757 .- 1873-4359. ; 302:03-jan, s. 197-203
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Tidskriftsartikel (refereegranskat)abstract
- The spreading of single styrene-acrylic latex particles on silicon oxide C surfaces was studied using atomic force microscopy (AFM). Three latexes with different glass transition temperature (Tg) were used and the effects of temperature, time and preparation method were investigated. Particle sizes and shape were measured with AFM and the contact angles were calculated. The observed rate for the spreading of latex particles was low and it took several days before the particles reached steady state, even at temperatures well above their T-g. The experimental particle spreading results deviated with two orders of magnitude from predictions Using the WLF equation for polymer diffusion. The deviation could be attributed to polymer-surface interactions that slowed down the particle spreading. The work of adhesion was calculated using two models. The results from using the regular Young-Dupre equation and a modified version of this equation that also included the mechanical properties (E-modulus and Poisson's ratio) of the latexes, were compared. For soft latex particles the results from the two models agreed well and were of the order of 75 J/m(2), but for glassy latexes the Young-Dupre equation underestimated the work of adhesion.
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| 5. |
- Gärdlund, Linda, et al.
(författare)
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New insights into the structure of polyelectrolyte complexes
- 2007
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Ingår i: Journal of Colloid and Interface Science. - : Elsevier BV. - 0021-9797 .- 1095-7103. ; 312:2, s. 237-246
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Tidskriftsartikel (refereegranskat)abstract
- The formation of polyelectrolyte complexes (PECs) from oppositely charged linear polyelectrolytes (PELs) was studied using static light scattering at various salt concentrations. The PELs used were poly(allylamine hydro chloride) (PAH) and the two polyanions poly(acrylic acid) (PAA) and poly(methacrylic acid) (PMAA). Physical characteristics such as the radii of gyration, molecular weights, and water contents of the PECs were determined at various molar mixing ratios. Despite relatively small differences in chemical structure between PAA and PMAA, fairly large differences were detected in these physical characteristics. Generally, PECs comprising PMAA were larger and contained more water. Moreover, by using cryogenic transmission electron microscopy, transmission microscopy and atomic force microscopy, shape and structure of the prepared PECs were investigated both in solution and after drying. The PECs were found to be spherical in solution and the shape was retained after freeze-drying. PECs adsorbed on silica surfaces and dried in air at room-temperature still showed a three-dimensional structure. However, the relatively low aspect ratios indicated that the PECs collapsed significantly due to interactions with the silica during adsorption and drying. At intermediate ionic strengths (1-10 mM), stagnation point adsorption reflectometry (SPAR) showed that the adsorption oflow charged cationic PAH-PAA PECs on silica surfaces increased if the pH value was increased from pH 5.5 to 7.5.
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| 6. |
- Gärdlund, Linda, et al.
(författare)
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The use of polyelectrolyte complexes (PEC) as strength additives for different pulps used for production of fine paper
- 2007
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Ingår i: Nordic Pulp & Paper Research Journal. - 0283-2631 .- 2000-0669. ; 22:2, s. 210-216
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Tidskriftsartikel (refereegranskat)abstract
- In this work the application of polyelectrolyte complexes (PEC) to different pulps, to improve the strength of papers produced from them, is compared with conventional pulp beating. The pulps chosen for the investigation were a fully bleached chemical hardwood pulp (HBK), a fully bleached chemical softwood pulp (SBK), and a peroxide-bleached chemithermomechanical pulp (BCTMP). The polyelectrolytes used were a polyamideamine epichlorohydrine condensate (PAE), traditionally used as a wet-strength additive, and carboxymethylcellulose. Since the prepared complexes had an anionic charge, they could only be used after fibre pre-treatment with the cationic PAE. Results indicate that the addition of 2% PAE and 2% PEC can improve all the measured tensile strength properties of the sheets as much as is commonly achieved by mechanically beating the pulps. In fact, for the chemical pulps, PEC addition at the chosen level produced better results than did traditional beating, since the improved tensile index and tensile energy absorption could be achieved without any significant deterioration in the light scattering coefficient of the papers produced. However, with the BCTMP a significant decrease in light scattering could be detected, especially following the addition of PEC. Adding the chemicals (especially the PEC) increased the sheet density and this together with the increase in the tensile stiffness, following chemical addition, resulted in a constant bending stiffness of the sheets. However, based on the results it can be suggested that a combination of unbeaten HBK and BCTMP treated with PAE and PEC can be used to produce a strong paper with a high bending stiffness.
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| 7. |
- Intarasiri, S., et al.
(författare)
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Crystalline quality of 3C-SiC formed by high-fluence C+-implanted Si
- 2007
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Ingår i: Applied Surface Science. - : Elsevier BV. - 0169-4332 .- 1873-5584. ; 253:11, s. 4836-4842
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Tidskriftsartikel (refereegranskat)abstract
- Carbon ions at 40 keV were implanted into (1 0 0) high-purity p-type silicon wafers at 400 degrees C to a fluence of 6.5 x 10(17) ions/cm(2). Subsequent thermal annealing of the implanted samples was performed in a diffusion furnace at atmospheric pressure with inert nitrogen ambient at 1100 degrees C. Time-of-flight energy elastic recoil detection analysis (ToF-E ERDA) was used to investigate depth distributions of the implanted ions. Infrared transmittance (IR) and Raman scattering measurements were used to characterize the formation of SiC in the implanted Si substrate. X-ray diffraction analysis (XRD) was used to characterize the crystalline quality in the surface layer of the sample. The formation of 3C-SiC and its crystalline structure obtained from the above mentioned techniques was finally confirmed by transmission electron microscopy (TEM). The results show that 3C-SiC is directly formed during implantation, and that the subsequent high-temperature annealing enhances the quality of the polycrystalline SiC.
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| 8. |
- Jaradeh, Majed, et al.
(författare)
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Analysis of solidification in a Bridgman furnace as a simulation of DC casting of aluminium alloy slabs
- 2007
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Ingår i: Materials Science and Technology. - 0267-0836 .- 1743-2847. ; 23:4, s. 475-482
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Tidskriftsartikel (refereegranskat)abstract
- The vertical Bridgman directional solidification equipment has been used in several investigations to simulate direct chill casting of wrought aluminium alloys. As a basis for such investigations and alloy developments, it is important to have an understanding of the performance of the furnace used during simulation of the casting conditions. In this investigation the thermal conditions in the furnace have been analysed in detail, both by measurements and by mathematical modelling. The growth characteristics of the furnace, such as gradient, growth rates and cooling rates have been compared to conditions in large ingots. The direct chill casting conditions, which the simulations have been compared to, are casting of slabs of 330 and 600 mm thickness of an aluminium AA3003 type alloy. The results show that the experiments are able to simulate the cooling conditions in the ingots except from the surface zone. Comparisons of the microstructures have been made and a good agreement has been obtained for structure parameters such as grain size and DAS.
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| 9. |
- Jaradeh, Majed, et al.
(författare)
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DTA and DSC Studies of Aluminium 3003 Alloys with Zn and Cu Additions
- 2007
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Ingår i: Metallurgical and Materials Transactions. A. - New York : Springer. - 1073-5623 .- 1543-1940. ; 38A, s. 2138-2147
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Tidskriftsartikel (refereegranskat)abstract
- The effect of Zn additions in the range of 0-5wt.% and Cu contents of 0.15-1.0 wt.%, on the solidification and precipitation behaviour of aluminium alloys of AA 3003 type was investigated with differential thermal analysis (DTA), differential scanning calorimetry (DSC), optical microscopy (OM), and scanning electron microscopy (SEM/EDX). The results show that the additions of varying Zn and Cu have significant effects on the crystallization process, phase precipitation and microstructure formation of the alloys. Phases formed have been identified and morphological differences have been discussed.
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| 10. |
- Jaradeh, Majed, et al.
(författare)
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Method Developed for Quantitative Assessment of Inclusions in Aluminium Billets
- 2007
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Ingår i: LIGHT METALS 2007. - : Minerals, Metals & Materials Society. - 9780873396592 ; , s. 679-684
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Konferensbidrag (refereegranskat)abstract
- A technique, based on sodium hydroxide hot macro etching, has been developed to deep etch non-metallic inclusions in a way that makes them visible on a macro scale. The distribution of inclusions in transverse sections along DC-cast aluminium billets could thus be studied. The technique has obvious advantages over other common analysis methods in giving a macroscopic spatial distribution of inclusions in a relatively simple way. The paper describes the development of the new technique and some applications. An analysis was made of how different inclusions behave during prolonged strong etching. Light optical microscopy, TEM and SEM/EDX have been used to identify specific inclusions.
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