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| 2. |
- Lundberg, Lars, et al.
(author)
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Using Golomb Rulers for Minimizing Collisions in Closed Hashing
- 2004
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Conference paper (peer-reviewed)abstract
- We give conditions for hash table probing which minimize the expected number of collisions. A probing algorithm is determined by a sequence of numbers denoting jumps for an item during multiple collisions. In linear probing, this sequence consists of only ones – for each collision we jump to the next location. To minimize the collisions, it turns out that one should use the Golomb ruler conditions: consecutive partial sums of the jump sequence should be distinct. The commonly used quadratic probing scheme fulfils the Golomb condition for some cases. We define a new probing scheme – Golomb probing - that fulfills the Golomb conditions for a much larger set of cases. Simulations show that Golomb probing is always better than quadratic and linear and in some cases the collisions can be reduced with 25% compared to quadratic and with more than 50% compared to linear.
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| 3. |
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Archives of ALGA, volume 1
- 2004
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Editorial collection (other academic/artistic)abstract
- Volume 1 contains 3 articles: Nail H. Ibragimov, Equivalence groups and invariants of linear and non-linear equations; Nail H. Ibragimov and Sergey V. Meleshko, Linearization of third-order ordinary differential equations; Nail H. Ibragimov, Gazanfer Ünal and Claes Jogreús, Group analysis of stochastic differential systems: Approximate symmetries and conservation laws.
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| 4. |
- Ibragimov, Nail H.
(author)
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Laplace type invariants for parabolic equations
- 2002
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In: Nonlinear dynamics. - DORDRECHT : KLUWER ACADEMIC PUBL. - 0924-090X .- 1573-269X. ; , s. 125-133
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Journal article (peer-reviewed)abstract
- The Laplace invariants pertain to linear hyperbolic differential equations with two independent variables. They were discovered by Laplace in 1773 and used in his integration theory of hyperbolic equations. Cotton extended the Laplace invariants to elliptic equations in 1900. Cotton's invariants can be obtained from the Laplace invariants merely by the complex change of variables relating the elliptic and hyperbolic equations. To the best of my knowledge, the invariants for parabolic equations were not found thus far. The purpose of this paper is to fill this gap by considering what will be called Laplace type invariants (or seminvariants), i.e. the quantities that remain unaltered under the linear transformation of the dependent variable. Laplace type invariants are calculated here for all hyperbolic, elliptic and parabolic equations using the unified infinitesimal method. A new invariant is found for parabolic equations.
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| 5. |
- Ibragimov, Nail H., et al.
(author)
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Symmetries of integro-differential equations : A survey of methods illustrated by the Benny equations
- 2002
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In: Nonlinear dynamics. - DORDRECHT : KLUWER ACADEMIC PUBL. - 0924-090X .- 1573-269X. ; , s. 135-153
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Journal article (peer-reviewed)abstract
- Classical Lie group theory provides a universal tool for calculating symmetry groups for systems of differential equations. However Lie's method is not as much effective in the case of integral or integro-differential equations as well as in the case of infinite systems of differential equations. This paper is aimed to survey the modern approaches to symmetries of integro-differential equations. As an illustration, an infinite symmetry Lie algebra is calculated for a system of integro-differential equations, namely the well-known Benny equations. The crucial idea is to look for symmetry generators in the form of canonical Lie-Backlund operators.
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| 6. |
- Kuzniarz, Ludwik, et al.
(author)
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Generating Domain Models from Ontologies.
- 2002
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In: International Conference on Object-Oriented Information Systems, LNCS, Springer. - Montpellier, France : SPRINGER-VERLAG BERLIN.
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Conference paper (peer-reviewed)abstract
- The paper presents and elaborates on the idea of automatic acquisition of knowledge about domain structure from ontologies into an object-oriented software development process. The information required to be included in the domain model produced during the development process is identified. The existence of the knowledge in ontologies is investigated. Requirements for ontology description languages are formulated followed by brief evaluation of existing languages against these requirements. A schema for domain knowledge acquisition is outlined. A realization of the schema is sketched in the paper while the implementation details can be found in the technical report.
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| 7. |
- Lundberg, Jenny, et al.
(author)
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Information exploration using the Pond
- 2002
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Conference paper (peer-reviewed)abstract
- In this paper we describe The Pond, a system used to search for and visualise data elements on an engaging tabletop display. The Pond uses methods of unencumbered interaction and audio feedback to allow users to investigate data elements, and supports shoulder-to-shoulder collaboration with the physical Pond artefact mediating the collaboration between those people gathered around it. The user interface is based on an ecosystem metaphor, presenting data elements in the form of shoals of aquatic creatures inside a virtual 3D pond. The Pond is an interactive system offering an appealing and novel way to search for and interchange information. We describe the motivation and design choices behind The Pond, the system as it stands today, details of its implementation, and observations from a study of The Pond in use.
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| 8. |
- Persson, Jan, 1972-, et al.
(author)
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A Tabu Search Heuristic for Scheduling the Production Processes at an Oil Refinery
- 2004
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In: International Journal of Production Research. - : Taylor & Francis. - 0020-7543 .- 1366-588X. ; 42:3, s. 445-471
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Journal article (peer-reviewed)abstract
- In this paper we present a tabu search heuristic which can be used for scheduling the production at an oil refinery. The scheduling problem is to decide which production modes to use at the different processing units at each point in time. The problem is a type of lot-sizing problem where costs of changeovers, inventories and production are considered. In the suggested tabu search heuristic we explore the use of variable neighbourhood, dynamic penalty and different tabu lists. Computational results are presented for different versions of the heuristic and the results are compared to the best-known lower bound for a set of scheduling scenarios.
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| 9. |
- Rakus-Andersson, Elisabeth
(author)
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The fuzzy development and adaptation of statistical and numerical methods to applications to technical and medical models with imprecise data
- 2002
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Other publication (other academic/artistic)abstract
- All the solutions to the problems sketched below will be created on the basis of Fuzzy Set Theory. Fuzzy Set Theory is applied instead of the classical set theory when data involved in the problem to solve is imprecise, verbally described or cannot be measured exactly. The models, which are the contents of the project should contain some proposed solutions to such problems as: 1) the approximation of the mean value and the standard deviation for some imprecise data, 2) a probability distribution filled with fuzzy probability sets (Yager’s probabilities) that replace the probability values from the normal distribution, 3) the application of the last distribution to statistical tests with imprecise data, 4) the development of Factor Analysis for qualitative variables and factors provided that the data is collected by means of a questionnaire, 5) the interpolation of a set of points with imprecise coordinates by a fuzzy function.
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| 10. |
- Rakus-Andersson, Elisabeth
(author)
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The Lattice of Verbal Fuzzy Numbers in IP-Traffic Prediction
- 2004
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Conference paper (peer-reviewed)abstract
- Fuzzy numbers constitute a helpful tool for some users who deal with imprecise data. To facilitate a procedure of performing operations on fuzzy numbers for these users who do not possess deep mathematical qualifications, we introduce a special space of fuzzy numbers verbally defined. This consists of families of fuzzy numbers in the L-R form provided that every family has a common mean value. We not only discuss some properties of the space, but also propose new conceptions of the arithmetical operations on the verbally expressed fuzzy numbers. The classification of the IP-traffic can act as a practical aspect, which clarifies the theoretical assumptions formulated in the paper.
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