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- Larsson, Mikael, 1982, et al.
(författare)
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Effect of calcium neutralization on elastic and swelling properties of crosslinked poly(acrylic acid) - correlation to inhomogeneities and phase behaviour
- 2009
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Ingår i: E-Polymers. - 1618-7229. ; :141, s. 1683-1696
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Tidskriftsartikel (refereegranskat)abstract
- Crosslinked hydrogels of poly(acrylic acid) neutralized with calcium hydroxide were synthesized using free radical co-polymerization. The effects of the amount added calcium on the elastic modulus and swelling properties of the gels and the correlation to phase behaviour and structural changes within the gels were studied using texture analysis, gravimetric analysis, scanning electron microscopy (SEM), energy dispersive X-ray (EDX) analysis and atomic force microscopy (AFM). It was found that the elastic modulus decreased nonlinearly with increasing amount of added calcium and that the swelling's dependence on the amount of added calcium was complicated. The maximum swelling increased with increasing amount of added calcium until a critical calcium content was reached, upon which the gels phase separated, with a strong decrease in swelling as a result. The changes in properties are explained by the fact that calcium affects the structure of the polymer network during synthesis and by the phase behaviour of the gels. Changes in the gel structure with the addition of calcium were detected with AFM. Furthermore, AFM revealed different phases on the nanometre scale for the sample with a calcium content around which phase separation is macroscopically observed. Finally, it was shown that the sulphur from the initiator potassium persulfate formed crystal like regions with high sulphur and calcium content upon drying of the hydrogels.
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| 5. |
- Nybacka, Mikael, et al.
(författare)
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Project: CASTT - Centre for Automotive Systems Technologies and Testing
- 2007
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Annan publikation (populärvet., debatt m.m.)abstract
- Through the Centre for Automotive Systems Technologies and Testing, Luleå University of Technology aims to first of all support automotive winter testing in Northern Sweden. This means to support the local automotive test entrepreneurs and through them their customers: the car manufacturers and their suppliers. To succeed in this task, the center relies on the university's areas of leading research and most importantly on the cooperation between those areas.
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- Schmidt, Henning, et al.
(författare)
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DESIREE as a new tool for interstellar ion chemistry
- 2008
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Ingår i: International Journal of Astrobiology. - 1473-5504 .- 1475-3006. ; 7:3-4, s. 205-208
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Tidskriftsartikel (refereegranskat)abstract
- A novel cryogenic electrostatic storage device consisting of two ion-beam storage rings with a common straight section for studies of interactions between oppositely charged ions at low and well-defined relative velocities is under construction at Stockholm University. Here we consider the prospect of using this new tool to measure cross-sections and rate coefficients for mutual neutralization reactions of importance in interstellar ion chemistry in general and specifically in cosmic pre-biotic ion chemistry.
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| 7. |
- Wang, Chuan, et al.
(författare)
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Integrated conceptual design of heating system at a Swedish mining company
- 2009
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Ingår i: Pres09 - 12th Conference Process Integration, Modelling and Optimisation for Energy Saving and Pollution Reduction. - : AIDIC Servizi S.r.l.. - 9788895608044 ; , s. 129-134
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Konferensbidrag (refereegranskat)abstract
- LKAB Malmberget is a Swedish mining site located at Malmberget, Sweden. Seven boiler centers are located on north part of Malmberget. There are no connections in between these boiler centers, meaning that it is a decentralized heating system. The heat generated is to heat up buildings and for mine ventilation mainly during the cold periods. The heat is mainly provided from electric and oil boilers. However, most boilers under use are over 20 years old, and it is time to retrofit the boiler system and infrastructure. The purpose of this work is to design and optimize the heating system by the integrated concept. An optimization model based on the mixed integer linear programming (MlLP) has been developed to minimize the total heat production cost, including operation cost and investment cost. The model can be used to calculate how a given heat demand can be satisfied at the lowest possible cost. Four different technical options have been considered in a new centralized heating system. On the basis of data input and assumptions, modeling results indicate that a lower cost could be achieved when a waste heat recovery boiler is installed at the old pelletization plant to recover sensible heat from flue gas. This will lead to a remarkable electricity saving (around 70% saving) compared to the reference case. It has also been noticed that in the optimized cases, oil boilers should not be operated due to a higher price compared to electricity, and by estimation an annual reduction of 3000 ton CO2 and 4.5 ton NOx could be achieved.
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- Abrahamsson, Maria, et al.
(författare)
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A new strategy for the improvement of photophysical properties in ruthenium(II) polypyridyl complexes. Synthesis and photophysical and electrochemical characterization of six mononuclear ruthenium(II) bisterpyridine-type complexes
- 2005
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Ingår i: Inorganic Chemistry. - : American Chemical Society (ACS). - 0020-1669 .- 1520-510X. ; 44:9, s. 3215-3225
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Tidskriftsartikel (refereegranskat)abstract
- The synthesis and characterization of six ruthenium(II) bistridentate polypyridyl complexes is described. These were designed on the basis of a new approach to increase the excited-state lifetime of ruthenium(II) bisterpyridine-type complexes. By the use of a bipyridylpyridyl methane ligand in place of terpyridine, the coordination environment of the metal ion becomes nearly octahedral and the rate of deactivation via ligand-field (i.e., metal-centered) states was reduced as shown by temperature-dependent emission lifetime studies. Still, the possibility to make quasi-linear donor-ruthenium-acceptor triads is maintained in the complexes. The most promising complex shows an excited-state lifet me of tau = 15 ns in alcohol solutions at room temperature, which should be compared to a lifetime of tau = 0.25 ns for [Ru(tpy)(2)](2+). The X-ray structure of the new complex indeed shows a more octahedral geometry than that of [Ru(tpy)(2)](2+). Most importantly, the high excited-state energy was retained, and thus, so was the potential high reactivity of the excited complex, which has not been the case with previously published strategies based on bistridentate complexes.
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| 9. |
- Adolfsson, Klas, 1972, et al.
(författare)
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Discretization of integro-differential equations modeling dynamic fractional order viscoelasticity
- 2006
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Ingår i: Lecture Notes in Computer Science, Springer, ''Proceedings of Large-Scale Scientific Computations, 2005, Sozopol, Bulgaria'', I. Lirkov, S. Margenov, and J. Wasniewski (Eds.). - 3540319948 ; 3743, s. 76-83
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Konferensbidrag (refereegranskat)abstract
- We study a dynamic model for viscoelastic materials based on a constitutive equation of fractional order. This results in an integro-differential equation with a weakly singular convolution kernel. We discretize in the spatial variable by a standard Galerkin finite element method. We prove stability and regularity estimates which show how the convolution term introduces dissipation into the equation of motion. These are then used to prove a priori error estimates. A numerical experiment is included.
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