| 1. |
- Aryasetiawan, F., et al.
(författare)
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Energy loss spectra and plasmon dispersions in alkali metals : Negative plasmon dispersion in Cs
- 1994
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Ingår i: Physical Review Letters. - : American Physical Society. - 0031-9007 .- 1079-7114. ; 73:12, s. 1679-1682
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Tidskriftsartikel (refereegranskat)abstract
- We present ab initio calculations of the energy loss spectra and plasmon dispersions of the alkali metals Na, K, Rb, and Cs within the random phase approximation, including band structure effects and core electrons as well as local field effects, due to inhomogeneity in the induced charge density. Band structure effects are found to cause a negative dispersion in Cs.
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| 2. |
- Berndtsson, Mikael
(författare)
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Management of Rules in Object-Oriented Databases
- 1994
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Ingår i: Proceedings of the Baltic Workshop on National Infrastructure Databases. ; , s. 78-85
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Konferensbidrag (refereegranskat)abstract
- This paper proposes a new approach to associating rules with events in object-oriented database systems. In it we propose a new run time mechanism, which associates rules with specific event definitions. This provide a basis for indexing rules by event definitions, which reduces rule checking to a minimum. The proposed subscription mechanism is general, in that it can be applied to both primitive events and composite events. Both rules and events are represented as first class objects. This architecture has been adopted in the ACOOD2 prototype on top of ONTOS.
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| 3. |
- Berndtsson, Mikael, et al.
(författare)
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On Developing Reactive Object-Oriented Databases
- 1992
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Ingår i: IEEE Data Engineering Bulletin. ; 15:1-4, s. 31-34
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Tidskriftsartikel (refereegranskat)abstract
- This paper outlines the ongoing work in Reactive Object-oriented Database Systems between the Departments of Computer Science in the University of Exeter(UK) and the University of Skovde(Sweden). The group is currently designing a monitoring system based on a reactive object oriented database with the objective of supporting efficient interaction between the active DBMS and applications (including intelligent systems). Initial work has centered on a prototype reactive object-oriented system built on top of ONTOS, a commercial OODBMS which has C++ as its base language. The prototype is referred to as ACOOD (ACtive Object Oriented Database system). We briefly discuss this prototype, showing how reactive behaviour has been incorporated into a full OODBMS albeit with some restrictions. We also outline our plans for its future extensions, and how these are motivated.
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| 4. |
- Berndtsson, Mikael
(författare)
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Reactive Object-Oriented Databases and CIM
- 1994
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Ingår i: Database and Expert Systems Applications. - Berlin : Springer. - 9783540584353 - 0387584358 - 3540584358 ; , s. 769-778
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Konferensbidrag (refereegranskat)abstract
- This paper propose a simple and powerful approach to associating rules with events in reactive object-oriented database systems. In it we propose a new run time subscription mechanism, which associates rules with specific event definitions. This brings optimization considerations - when to fire a rule - to the language level. The proposed subscription mechanism reduces rule checking to a minimum. It can be applied to both primitive and composite events. Both rules and events are represented as first class objects. This architecture has been adopted in the ACOOD2 prototype on top of ONTOS.
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| 5. |
- Bodén, Mikael, et al.
(författare)
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A Connectionist Model of Nonmonotonic Reasoning : Handling Exceptions in Inheritance Hierarchies
- 1992
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Nonmonotonic reasoning is a core problem in AI. An example of nonmonotonic reasoning is the type of default reasoning which occurs with inheritance structures which allow exceptions. This paper describes a connectionist model of a hierarchical inheritance structure with exceptions. Existing symbolic and related connectionist research are described, and their limitations summarized. The requirements for an adaptable connectionist model are laid out, and a representational architecture is constructed. The architecture requires relations (i.e. links between objects) to be bi-directional or directional, where the former is meant to capture those relations for which it is useful to have the inverse relation (e.g. `isa', `part-of'). The general assumption is that inferential distances are best captured by relying on representational similarities in the semantic features of tokens and types. Both the encoding mechanism and the decoding mechanism (for checking the uniqueness of the distributed representations) are described in detail. The representational architecture is implemented in recursive autoassociative memory. The model is successful, and future adaptation or handling multiple inheritance with exceptions is briefly explored.
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| 6. |
- Bodén, Mikael, et al.
(författare)
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A Representational Architecture for Nonmonotonic Inheritance Structures
- 1993
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- This paper describes a connectionist system for representing and reasoning with multiple inheritance structures with exceptions. The representational architecture has three characteristics. First, it merges relational with taxonomic representations. Secondly, it handles conflicts generated by exceptions and the use of multiple superclasses. Thirdly, it uses fully distributed representations. One novel feature is that, since the distributed representation of an entity is influenced by its position in the inheritance structure, representations of assertions are influenced by the context of the entities. An extension to the model which implements and makes use of confluent inference is described.
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| 7. |
- Chauhan, H. S., et al.
(författare)
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Direct- and inverse-photoemission investigations of the electronic structure of Cd(0001)
- 1993
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Ingår i: Physical Review B Condensed Matter. - : American Physical Society. - 0163-1829 .- 1095-3795. ; 48:7, s. 4729-4734
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Tidskriftsartikel (refereegranskat)abstract
- Photoemission and inverse angle-resolved photoemission spectra are presented for Cd(0001). The data are interpreted in terms of interband transitions, density-of-states effects, and excitations of surface states.
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| 8. |
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| 9. |
- Karlsson, Krister, 1961-, et al.
(författare)
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Chemical shifts for monovalent, divalent and trivalent Cu compounds
- 1992
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Ingår i: Journal of Physics. - : Institute of Physics Publishing (IOPP). - 0953-8984 .- 1361-648X. ; 4:3, s. 895-909
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Tidskriftsartikel (refereegranskat)abstract
- The authors study the chemical shift of the Cu 2p core level for Cu 2O, CuO and NaCuO2, where Cu is formally monovalent, divalent and trivalent, respectively. They find that the binding energy increases with the valence, as expected, although the variation in the number of 3d electrons is small and the trivalent Cu atom is found to have a smaller net positive charge than the monovalent or divalent Cu. The origin of the calculated chemical shifts is analysed and the relation with the chemical valence is discussed.
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| 10. |
- Karlsson, Krister, 1961-, et al.
(författare)
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Cu 2p chemical shifts for YBa2Cu3O6.5 : Valence of the Cu atoms
- 1992
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Ingår i: Physical Review B Condensed Matter. - : American Physical Society. - 0163-1829 .- 1095-3795. ; 45:13, s. 7559-7562
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Tidskriftsartikel (refereegranskat)abstract
- We study the chemical shift of three different Cu atoms in YBa2Cu3O6.5, and compare the results with the formally mono-, di-, and trivalent model compounds Cu2O, CuO, and NaCuO2. We find similar chemical shifts between Cu in the empty chains, Cu in the planes, and Cu in the intact chains as between the Cu atoms in the model compounds. This suggests that the different Cu atoms in YBa2Cu3O6.5 have formal valences of approximately 1,2, and 3. © 1992 The American Physical Society.
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