| 51. |
- Carlsson, Janne
(författare)
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Methods for mechanical testing based on analysis of elastic waves in rods
- 1992
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis summarizes six papers on development and applications of a method to evaluate the normal force and particle velocity at any cross-section of a nonuniform rod from measurements of strain at two different cross-sections. In Paper A the method is developed. It is an extension of that developed by Lundberg and Henchoz for uniform rods. Theoretical results, based on onedimensional elastic wave theory, are provided for the general case as well as for cases of piecewise constant characteristic impedance. In Paper B an extension of the method has been used to determine the characteristic impedance function for an initially uniform rod heated at one end. The results show that force and particle velocity at the heated end can be evaluated with the same accuracy as for a uniform rod. In Paper C the method has been used to extend the split-Hopkinson pressure bar technique to testing of high-strength materials such as ceramics. The technique gives an accurate value of the fracture stress and a fair approximation of the strain rate. A modified Hopkinson pressure bar has been used in Paper D to determine the dynamic fracture toughness from the load-point displacement of a three-point bend specimen. The latter quantity was assumed to be proportional to the stress intensity factor. The results agreed well with those obtained from strain measurement near the notch tip. From the penetration tests made in Paper E it was concluded that the method established allows force-penetration data to be determined satisfactorily for standard threaded rod-bit configurations. Paper F presents a rod transducer for rotational point mobility. The tests showed that the transducer works satisfactorily in frequency and mobility ranges of approximately two decades.
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| 52. |
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| 53. |
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| 54. |
- Carlsson, Svante
(författare)
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A note on HEAPSORT
- 1992
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Ingår i: Computer journal. - : Oxford University Press (OUP). - 0010-4620 .- 1460-2067. ; 35:4, s. 410-411
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- In The Computer Journal 33 (3), 1990, Xunrang and Yuzhang presented a new algorithm for HEAPSORT to reduce the number of comparisons from 2n lg n comparisons to ¾n lg n in the worst case. By recursing on their technique we show how the cost can be reduced to n lg n + n lg lg n comparisons. Combining this with another known technique that has the same complexity, we shall achieve the optimal solution for deleting the maximum element from a heap. Using this for sorting we get slightly less than n lg n + n lg* n comparisons.
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| 55. |
- Carlsson, Svante, et al.
(författare)
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In-place linear probing sort
- 1992
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Ingår i: STACS 92. - Berlin, Heidelberg : Encyclopedia of Global Archaeology/Springer Verlag. - 3540552103 ; , s. 581-587
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Konferensbidrag (refereegranskat)abstract
- We introduce the first sorting algorithm that is proven to sort n randomly drawn uniformly distributed elements in O(n) time in situ. The constants in this algorithm are small, and simulations have shown it competitive with other sorting algorithms. It is, furthermore, conceptually simple and easy to code, which makes it a practical distributive sorting algorithm.
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| 56. |
- Carlsson, Svante, et al.
(författare)
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On partitions and presortedness of sequences
- 1992
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Ingår i: Acta Informatica. - 0001-5903 .- 1432-0525. ; 29:3, s. 267-280
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Tidskriftsartikel (refereegranskat)abstract
- To take advantage of existing order in a sequence when sorting, we evaluate the quantity of this information by the minimal size of decomposition of the input sequence, particularly the minimal size of chain and of monotonic partitions. Some sorting strategies that are optimal with respect to these measures of presortedness are presented. The relationships between these new measures of presortedness and other known measures have also been explored. As an application, we carry out the optimality of an adaptive sorting algorithm Skiena'sMelsort. For some special partitioning strategies, we present two sorting algorithms based on Dijkstra'sSmoothsort. Moreover, the optimalities of these two algorithms are demonstrated. By examining the optimalities of sorting algorithms with respect to certain measures of presortedness, we also propose some optimal sorting strategies for one class of measures. Finally, we discuss other types of sorting problems, such as sorting multisets and topological sorting. In particular, we derive an optimal algorithm for sorting multisets and for finding the multiset sizes as well.
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| 57. |
- Carlsson, Svante, et al.
(författare)
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Parallel complexity of heaps and min-max heaps
- 1992
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Ingår i: LATIN '92. - Berlin : Encyclopedia of Global Archaeology/Springer Verlag. - 3540552847 ; , s. 108-116
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Konferensbidrag (refereegranskat)abstract
- We study parallel solutions to the problem of implementing priority queues and priority deques. It is known that data structures for the implementation (e.g., the heap, the minmax heap, and the deap) can be constructed in linear sequential time. In this paper, we design optimal Ω((log log n)2) time parallel algorithms with n/(log logn)2 processors for the constructions on the parallel comparison tree model. For building heaps in parallel, our algorithm improves the previous best result of Ω(log n) time with n/log n processors. For building min-max heaps and deaps, our algorithms are the first attempt to design parallel algorithms for constructing the data structures of the priority deque that are cost optimal.
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| 58. |
- Carlsson, Svante, et al.
(författare)
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Parallel constructions of heaps and min-max heaps
- 1992
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Ingår i: Parallel Processing Letters. - 0129-6264 .- 1793-642X. ; 2:4, s. 311-320
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Tidskriftsartikel (refereegranskat)abstract
- The authors study parallel solutions to the problem of implementing priority queues and priority deques. It is known that data structures for the implementation (e.g. the heap, the min-max heap, and the deap) can be constructed in linear sequential time. They design optimal Θ((log log n)2) time parallel algorithms with n/(loglogn)2 processors for the constructions in the parallel comparison tree model
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| 59. |
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| 60. |
- Chaesson, Johan, et al.
(författare)
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Conformal flow models for warm and cold storage in aquifers
- 1992
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Ingår i: Proceedings of the Intersociety Energy Conversion Engineering Conference. - 0146-955X. ; 4, s. 125-129
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Tidskriftsartikel (refereegranskat)abstract
- The paper presents the thermohydraulic models for aquifer thermal energy storage developed by the Lund Group for Ground Heat. The basic assumption is that the aquifer is horizontally homogeneous and that the groundwater flow is two-dimensional without a vertical component. The groundwater flow field is then given by an analytical function, or conformal transformation, which is obtained from the positions of the well, the pumping rates, and the regional flow. The first set of PC models concerns the groundwater flow and the motion of thermal fronts for any set of wells and a regional flow. The flow field, with streamlines and stagnation points, is presented graphically on the screen. The motion of the thermal fronts is determined by particle tracking. These interactive models have proven to be very convenient and useful design tools. The complete three-dimensional thermal process is solved in the second set of PC models. The groundwater flow is again given by the explicit analytical formulas, while the thermal process is solved numerically. The coupled groundwater and the heat flow process in the aquifer is dealt with using a new entropy-conservation technique. The models are carefully documented and available on PC. They have been validated against a few field experiments and they are used extensively for design studies
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