| 1. |
- Andersson, Arne, et al.
(författare)
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A New Analysis of Combinatorial vs Simultaneous Auctions: Revenue and Efficiency
- 2008
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- We address the fundamental issue of revenue and efficiency in the combinatorial and simultaneous auction using a novel approach. Specifically, upper and lower bounds are constructed for the first-price sealed-bid setting of these two auctions. The question of revenue is important yet very few results can be found in the literature. Only for very small instances with 2 items have comparisons been made. Krishna et. al. find that allowing combinatorial bids result in lower revenue compared to a second price simultaneous auction. We formulate a lower bound on the first-price combinatorial auction and an upper bound on the first-price simultaneous auction for larger problems with several items and many bidders, in a model where bidders have synergies from winning a specific set of items. We show that the combinatorial auction is revenue superior to the simultaneous auction for a specific instance in pure symmetric equilibrium and give two generalized upper bounds on revenue for the simultaneous auction.
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| 2. |
- Andersson, Arne, et al.
(författare)
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A New Analysis of Revenue in the Combinatorial and Simultaneous Auction
- 2009
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- We prove that in many cases, a first-price sealed-bid combinatorial auction gives higher expected revenue than a sealed-bid simultaneous auction. This is the first theoretical evidence that combinatorial auctions indeed generate higher revenue, which has been a common belief for decades.We use a model with many bidders and items, where bidders are of two types: (i) single-bidders interested in only one item and (ii) synergy-bidders, each interested in one random combination of items. We provide an upper bound on the expected revenue for simultaneous auctions and a lower bound on combinatorial auctions. Our bounds are parameterized on the number of bidders and items, combination size, and synergy.We derive an asymptotic result, proving that as the number of bidders approach infinity, expected revenue of the combinatorial auction will be higher than that of the simultaneous auction. We also provide concrete examples where the combinatorial auction is revenue-superior.
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| 3. |
- Andersson, Arne, et al.
(författare)
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A study of the ageing and deactivation phenomena occurring during operation of an iron molybdate catalyst in formaldehyde production
- 2006
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Ingår i: Catalysis Today. - : Elsevier BV. - 0920-5861. ; 112:1-4, s. 40-44
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Tidskriftsartikel (refereegranskat)abstract
- Catalyst from a Perstorp Formox formaldehyde plant, operating with high inlet concentration of methanol (10.2 vol.%), was discharged from single tubes of a multi-tube reactor after half the expected lifetime of the catalyst and again after termination of the load. Each tube was filled with two different layers of catalyst. From the inlet of the reactor the first layer was a catalyst mixed with inert rings, which was followed by a second layer of pure catalyst extending from the middle to the outlet of the reactor. Catalyst fractions from the two layers were characterized with various techniques including BET, Fourier transform Raman (FT-Raman) spectroscopy, X-ray diffraction (XRD), elemental analysis with atomic absorption spectroscopy (AAS) and activity measurements. It was found that the surface area of the catalyst in the mixed layer increases during operation while a small decrease is noticeable for the catalyst below in the pure layer. Elemental analysis, XRD and FT-Raman show that during operation of the catalyst there is migration of Mo species from the upper part of the reactor towards the outlet. Activity measurements reveal severe deactivation of the catalyst in the mixed layer. It is concluded that the deactivation primarily is due to formation of volatile species formed by the MoO3 surface reacting methanol, causing a decrease of the MoO3/Fe-2(MoO4)(3) mole ratio in the catalyst. Concerning the catalyst in the pure layer, the condensation of needle-like crystals of MoO3 mainly occurs on the external surface of the catalyst ring.
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| 4. |
- Andersson, Arne, et al.
(författare)
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Amyloid Deposition in Transplanted Human Pancreatic Islets : A Conceivable Cause of Their Long-Term Failure
- 2008
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Ingår i: EXPERIMENTAL DIABETES RESEARCH. - : Hindawi Limited. - 1687-5214 .- 1687-5303. ; 2008:562985
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Tidskriftsartikel (refereegranskat)abstract
- Following the encouraging report of the Edmonton group, there was a rejuvenation of the islet transplantation field. After that, more pessimistic views spread when long-term results of the clinical outcome were published. A progressive loss of the beta-cell function meant that almost all patients were back on insulin therapy after 5 years. More than 10 years ago, we demonstrated that amyloid deposits rapidly formed in human islets and in mouse islets transgenic for human IAPP when grafted into nude mice. It is, therefore, conceivable to consider amyloid formation as one potential candidate for the long-term failure. The present paper reviews attempts in our laboratories to elucidate the dynamics of and mechanisms behind the formation of amyloid in transplanted islets with special emphasis on the impact of long-term hyperglycemia.
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| 5. |
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| 6. |
- Andersson, Arne
(författare)
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Balanced Binary Search Trees
- 2005
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Ingår i: Handbook of Data Structures and Applications. - : CRC Press. - 1584884355 ; , s. 1392-
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Bokkapitel (övrigt vetenskapligt/konstnärligt)
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| 7. |
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| 8. |
- Andersson, Arne, et al.
(författare)
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Dynamic Ordered Sets with Exponential Search Trees
- 2007
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Ingår i: Journal of the ACM. - : Association for Computing Machinery (ACM). - 0004-5411 .- 1557-735X. ; 54:3, s. 1236460-
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Tidskriftsartikel (refereegranskat)abstract
- We introduce exponential search trees as a novel technique for converting static polynomial space search structures for ordered sets into fully-dynamic linear space data structures. This leads to an optimal bound of O(log n/log log n) for searching and updating a dynamic set X of n integer keys in linear space. Searching X for an integer y means finding the maximum key in X which is smaller than or equal to y. This problem is equivalent to the standard text book problem of maintaining an ordered set. The best previous deterministic linear space bound was O(log n/log log n) due to Fredman and Willard from STOC 1990. No better deterministic search bound was known using polynomial space. We also get the following worst-case linear space trade-offs between the number n, the word length W, and the maximal key U < 2W: O(min log log n + log n/logW, log log n log log U/log log log U). These trade-offs are, however, not likely to be optimal. Our results are generalized to finger searching and string searching, providing optimal results for both in terms of n.
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| 9. |
- Andersson, Arne, et al.
(författare)
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Dynamic String Searching
- 2001
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Ingår i: ACM-SIAM symposium on Discrete algorithms, SODA.
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Konferensbidrag (refereegranskat)
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| 10. |
- Andersson, Arne, et al.
(författare)
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Efficient resource allocation with non-concave objective functions
- 2001
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Ingår i: Computational Optimization and Applications. - 0926-6003. ; 20:3, s. 281-298
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Tidskriftsartikel (refereegranskat)abstract
- We consider resource allocation with separable objective functions defined over subranges of the integers. While it is well known that (the maximization version of) this problem can be solved efficiently if the objective functions are concave, the general
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