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- Edvardsson, Hannes, et al.
(författare)
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Compact and efficient 3D shape description through radial function approximation
- 2003
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Ingår i: Computer Methods and Programs in Biomedicine. - 0169-2607 .- 1872-7565. ; 72:2, s. 89-97
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Tidskriftsartikel (refereegranskat)abstract
- A fast and simple method for three-dimensional shape description is described. The method views a 3D object as a radial distance function on the unit sphere, and thus reduces the dimensionality of the description problem by one. The radial distance function is approximated by Fourier methods in the basis of the spherical harmonic polynomials. The necessary integration is carried out on the object boundary, rather than on the unit sphere. Consequently, there is no need of a parameterisation of the object surface. The description makes it possible to compare shapes in a computationally very simple way. Solutions on how to cope with translated and rotated objects are discussed. The method is developed for star-shaped objects, but is stable even if the input image is non-star-shaped. The method is tested in a data set from magnetic resonance imaging (MRI) of the brain. Potential medical applications are discussed. ⌐ 2002 Elsevier Science Ireland Ltd. All rights reserved.
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| 2. |
- Kannisto, Hannes, 1979, et al.
(författare)
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Efficient low temperature lean NOx reduction over Ag/Al2O3-A system approach
- 2011
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Ingår i: Applied Catalysis B: Environmental. - : Elsevier BV. - 0926-3373 .- 1873-3883. ; 104:1-2, s. 74-83
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Tidskriftsartikel (refereegranskat)abstract
- This study focuses on lean NOx reduction (LNR) by n-octane using silver-alumina based catalysts, with the addition of hydrogen. The work takes a system approach, where parameters such as temperature, reformate gas composition, fuel penalty and realistic monolith samples are considered. The LNR catalyst samples were prepared by impregnation and sol-gel methods and the NOx reduction performance was characterized by flow-reactor experiments, where realistic engine-out gas compositions were used. The hydrogen feed over the LNR catalyst samples was determined via data achieved by autothermal reforming experiments over a rhodium based catalyst, using real diesel as feedstock. The LNR catalyst samples generally show an enhanced NOx reduction when hydrogen is added to the gas feed. In particular, a 2 wt% silver-alumina sample with the addition of minute amounts of platinum, shows a high increase in NOx reduction when hydrogen is added to the feed. The addition of CO, a potential poison in the reaction and a by-product from the reforming, did not show any significant effect on the LNR catalyst performance at the conditions used. This is beneficial, since it renders a CO clean-up step in the reformer system unneeded. Ammonia formation is discussed in terms of a possible dual-SCR system. Finally, the fuel penalty for hydrogen production and hydrocarbon addition is taken into consideration. It is found that an addition of 1000 ppm H-2 leads to unacceptable fuel penalties. (C) 2011 Elsevier B.V. All rights reserved.
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