| 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. |
- 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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| 3. |
- Engholm, Magnus, et al.
(författare)
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Improved photodarkening resistivity in ytterbium-doped fiber lasers by cerium codoping
- 2009
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Ingår i: Optics Letters. - 0146-9592 .- 1539-4794. ; 34:8, s. 1285-1287
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Tidskriftsartikel (refereegranskat)abstract
- We show that the photodarkening resistivity of ytterbium-doped fiber lasers can be greatly improved by cerium codoping. It is suggested that the coexistence of the redox couple Ce3+⁄Ce4+ in the glass provides means for trapping both hole- and electron-related color centers that are responsible for the induced optical losses in Yb-doped fiber lasers.
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| 4. |
- Halvarsson, Sören, et al.
(författare)
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Manufacture of non-resin wheat straw fibreboards
- 2009
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Ingår i: Industrial crops and products (Print). - : Elsevier BV. - 0926-6690 .- 1872-633X. ; 29:2-3, s. 437-445
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Tidskriftsartikel (refereegranskat)abstract
- Wheat straw was used as raw material in the production of fibreboards. The size-reduced straw was pretreated with steam, hot water and sulphuric acid before the defibration process to loosen its physical structure and reduce the pH. No synthetic binder was added. Adhesive bonding between fibres was initiated by activation of the fibre surfaces by an oxidative treatment during the defibration process. Fenton's reagent (ferrous chloride and hydrogen peroxide) was added. Two different levels of hydrogen peroxide (H2O2), 2.5% or 4.0% were used. The resulting fibres were characterized in terms of fibre length distribution, shive content, pH and pH-buffering capacity. The properties of finished fibreboards were compared with medium-density fibreboard (MDF) with density above 800 kg/m(3) produced from straw and melamine modified UF resin. The modulus of rupture (MOR), modulus of elasticity (MOE) and internal bond (IB) were lower than those of conventional manufactured wheat straw fibreboards but close to the requirements of the MDF standard (EN 622-5: 2006). The water absorption properties for the H2O2 activated straw fibreboards were relatively high, but were reduced by 25% with the addition of CaCl2 into the defibrator system as a water-repelling agent. Increased levels of hydrogen peroxide improved the mechanical and physical properties of the straw fibreboard. Crown
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| 5. |
- Holmgren, Anders, et al.
(författare)
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On the role of the monolignol gamma-carbon functionality in lignin biopolymerization
- 2009
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Ingår i: Phytochemistry. - : Elsevier BV. - 0031-9422 .- 1873-3700. ; 70:1, s. 147-155
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Tidskriftsartikel (refereegranskat)abstract
- In order to investigate the importance of the monomeric gamma-carbon chemistry in lignin biopolymerization and structure, synthetic lignins (dehydrogenation polymers; DHP) were made from monomers with different degrees of oxidation at the gamma-carbon, i.e., carboxylic acid, aldehyde and alcohol. All monomers formed a polymeric material through enzymatic oxidation. The polymers displayed similar sizes by size exclusion chromatography analyses, but also exhibited some physical and chemical differences. The DHP made of coniferaldehyde had poorer solubility properties than the other DHPs, and through contact angle of water measurement on spin-coated surfaces of the polymeric materials, the DHPs made of coniferaldehyde and carboxylic ferulic acid exhibited higher hydrophobicity than the coniferyl alcohol DHP. A structural characterization with C-13 NMR revealed major differences between the coniferyl alcohol-based polymer and the coniferaldehyde/ferulic acid polymers, such as the predominance of aliphatic double bonds and the lack of certain benzylic structures in the latter cases. The biological role of the reduction at the gamma-carbon during monolignol biosynthesis with regard to lignin polymerization is discussed.
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| 6. |
- Högberg, Lovisa, et al.
(författare)
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Incentives for improving energy efficiency when renovating large-scale housing estates : A Case Study of the Swedish Million Homes Programme
- 2009
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Ingår i: Sustainability. - : MDPI AG. - 2071-1050. ; 1:4, s. 1349-1365
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Tidskriftsartikel (refereegranskat)abstract
- Sweden has adopted ambitious energy savings objectives for buildings, but at the current rate of energy efficiency investments the objectives are unlikely to be reached. In this article we report the early findings of how real estate owners reason and act in energy efficiency investment decisions. Based on the results from interviews with the real estate companies, the companies have been divided into four ideal types that illuminate the differences in energy efficiency ambition and strategies; the Strict Profit Maximizing Company, the Little Extra Company, the Policy Led Ambitious Company and the Administration Led Ambitious Company. The different strategies will determine how the companies respond to incentives to invest in energy efficiency, and affect the overall result in the energy efficiency work. The ideal types hence are important to have in mind when designing policies to increase energy efficiency.
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| 7. |
- Johansson, Erik, et al.
(författare)
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Adsorption Behavior and Adhesive Properties of Biopolyelectrolyte Multilayers formed from Cationic and Anionic Starch
- 2009
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Ingår i: Biomacromolecules. - : American Chemical Society (ACS). - 1525-7797 .- 1526-4602. ; 10:7, s. 1768-1776
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Tidskriftsartikel (refereegranskat)abstract
- Cationic starch (D.S. 0.065) and anionic starch (D.S. 0.037) were used to form biopolyelectrolyte multilayers. The influence of the solution concentration of NaCl on the adsorption of starch onto silicon oxide substrates and on the formation of multilayers was investigated using stagnation point adsorption reflectometry (SPAR) and quartz crystal microbalance with dissipation (QCM-D). The wet adhesive properties of the starch multilayers were examined by measuring pull-off forces with the AFM colloidal probe technique. It was shown that polyelectrolyte multilayers (PEM) can be successfully constructed from cationic starch and anionic starch at electrolyte concentrations of 1 mM NaCl and 10 mM NaCl. The water content of the PEMs was approximately 80% at both electrolyte concentrations. However, the thickness of the PEMs formed at 10 mM NaCl was approximately twice the thickness formed at I mM NaCl. The viscoelastic properties of the starch PEMs, modeled as Voigt elements, were dependent on the polyelectrolyte that was adsorbed in the outermost layer. The PEMs appeared to be more rigid when capped by anionic starch than when capped by cationic starch. The wet adhesive pull-off forces increased with layer number and were also dependent oil the polyelectrolyte adsorbed in the outermost layer. Thus, starch PEM treatment has a large potential for increasing the adhesive interaction between solid substrates to levels higher than can be reached by a single layer of cationic starch.
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| 8. |
- Kulachenko, Artem, et al.
(författare)
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Strength of wet fiber networks-Strength scaling
- 2009
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Ingår i: Papermaking Research Symposium 2009. - Kuopio : University of Kuopio. - 9789512710164 ; , s. 35-
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)
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| 9. |
- Lindström, Stefan B, 1974-, et al.
(författare)
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New insights in paper forming from particle-level process simulations
- 2009
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Ingår i: Papermaking Research Symposium 2009. - Kuopio, Finland : University of Kuopio. - 9789512710164 ; , s. 38-
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- By virtue of the recent developments in simulation techniques for fibre suspensions flows, it is now possible to directly simulate forming of the paper sheet at a particle level under realistic flow conditions. This opens up a window of opportunity to better understand the microscale development of the paper structure, and to attribute particular features of the structure to different drainage elements.The simulations are based on a particle-level fibre suspension model, in which fibres are represented by chains of cylindrical fibre segments. The fibre model includes curled shapes and the torsion and bending of the fibres. It also captures the two-way interactions between the fibres and the fluid phase. The fluid motion is integrated from the Navier--Stokes equations.To illustrate the usage of the simulation tool, a sample parametric study of the effects of different fibre furnishes on the paper structure and wet strength is presented. Such an investigation could almost as easily have been performed with experiments. Simulations, however, have some advantages: First, the cost is almost nothing as compared to pilot trials. Secondly, the parameters of the simulations can be controlled one at a time, whereas in pilot trials, changing one process parameter will affect the others. Thirdly, every detail of the evolving paper structure is accessible at every instant in the simulations. That is, the forming process needs no longer be considered a "black box". Simulations also have some drawbacks. For instance, it is not possible to include the smallest particles, due to their vast number, while maintaining sufficiently large flow geometry. Therefore, simulations must target paper grades of low fines contents.In this communication, the pros and cons of particle-level simulations are discussed, and put into the context of previous forming and dewatering models in the literature. The development of the paper microstructure predicted in the simulations shows that thickening is the dominant forming mechanism, while filtration only occurs in the most dilute end of the typical range of consistencies used in the industry. This predicted behaviour is compared with the conventional view of dewatering, which holds filtration as the dominant forming mechanism.
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| 10. |
- Mbairi, Felix D., et al.
(författare)
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Microwave bandstop filters using novel artificial periodic substrate electromagnetic band gap structures
- 2009
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Ingår i: IEEE transactions on components and packaging technologies (Print). - 1521-3331 .- 1557-9972. ; 32:2, s. 273-282
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Tidskriftsartikel (refereegranskat)abstract
- Novel microwave and millimeterwave (mm-wave) bandstop filters using artificial periodic substrate electromagnetic bandgap (EBG) are investigated in this paper. Three types of microstrip structures using periodically modified trace width, patterned dielectric substrate, and periodically modified ground plane are treated, respectively. By periodically modifying either the width of the conductor trace, the substrate height, or the dielectric constant of a standard microstrip transmission line, it has been possible to design microwave bandstop filter functions with wide stopband characteristics and reduced size, compared to conventional microwave/RF filter structures. Commercial electronic design automation (EDA) and computational electromagnetic tools such as Agilent's advanced design system (ADS) and CST Microwave Studio are used in the design and simulations of these filter structures. The effects of the physical parameters of the structures on the filter characteristic are studied. The design procedure and simulation results are described and possible applications of these filter structures are discussed in this paper. A particularly wide stopband is achieved by the circuits presented in this paper, which use only a few cell elements. A significant performance improvement of microstrip patch antenna has been observed by implementing one of the presented EBG periodic substrate structures.
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