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91.
Modal Kleene algebras are Kleene algebras enriched by forward and backward box and diamond operators. We formalise the symmetries of these operators as Galois connections, complementarities and dualities. We study their properties in the associated operator algebras and show that the axioms of relation algebra are theorems at the operator level. Modal Kleene algebras provide a unifying semantics for various program calculi and enhance efficient cross-theory reasoning in this class, often in a very concise pointfree style. This claim is supported by novel algebraic soundness and completeness proofs for Hoare logic and by connecting this formalism with an algebraic decision procedure. 相似文献
92.
Georg Pohlner Zoran Vujic Manfred Bürger Günter Lohnert 《Nuclear Engineering and Design》2006,236(19-21):2026-2048
The objective of the development of the code system KESS is simulating the processes of core melting, relocation of core material to the lower head of the reactor pressure vessel (RPV) and its further heatup, modelling of fission product release and coolability of the core material. In the scope of the code development, IKEJET and IKEMIX were designed as key models for the breakup of a molten jet falling into a water pool, cooling of fragments and the formation of particulate debris beds. Calculations were performed with these codes, simulating FARO corium quenching experiments at saturated (L-28) and subcooled (L-31) conditions, as well as PREMIX experiments, e.g. PM-16. With the assumption of a reduced interfacial friction between water and steam as compared to usually applied laws, the melt breakup, energy release from the melt and pressurisation of the vessel observed in the experiments are reproduced with a reasonable accuracy. The model is further applied to reactor conditions, calculating the relocation of a mass of corium of 30 t into the lower plenum, its fragmentation and the formation of a particle bed. 相似文献
93.
Propagation Models for Trust and Distrust in Social Networks 总被引:4,自引:0,他引:4
Semantic Web endeavors have mainly focused on issues pertaining to knowledge representation and ontology design. However,
besides understanding information metadata stated by subjects, knowing about their credibility becomes equally crucial. Hence,
trust and trust metrics, conceived as computational means to evaluate trust relationships between individuals, come into play.
Our major contribution to Semantic Web trust management through this work is twofold. First, we introduce a classification
scheme for trust metrics along various axes and discuss advantages and drawbacks of existing approaches for Semantic Web scenarios.
Hereby, we devise an advocacy for local group trust metrics, guiding us to the second part which presents Appleseed, our novel
proposal for local group trust computation. Compelling in its simplicity, Appleseed borrows many ideas from spreading activation
models in psychology and relates their concepts to trust evaluation in an intuitive fashion. Moreover, we provide extensions
for the Appleseed nucleus that make our trust metric handle distrust statements.
Cai-Nicolas Ziegler is a post-doctoral researcher at DBIS, the Databases and Information Systems group of the University of Freiburg, Germany.
He studied Computer Science at the University of Passau, Germany, and Université Laval, Québec, receiving his Diploma (equivalent
to MSc) in 2003. Cai-Nicolas obtained his PhD in Computer Science from the University of Freiburg in 2005.
His primary research interests cover collaborative filtering applications and recommender systems, as well as computational
trust models on the verge of human-computer interaction.
Georg Lausen is head of the research group on Databases and Information Systems (DBIS) at the University of Freiburg, Germany. He received
his Diploma in Industrial Engineering in 1978, PhD in 1982, and his postdoctoral lecture qualification (Habilitation) in 1985
from the University of Karlsruhe (TH). He was associate professor for Information Technology and Integration Problems at the
Technical University of Darmstadt from 1986 to 1987. From 1987 to 1994 he was full professor for databases and informations
systems at the University of Mannheim, and since 1994 at the University of Freiburg.
His current research interests comprise information integration, internet technologies, and Web services. 相似文献
94.
Georg Struth 《The Journal of Logic and Algebraic Programming》2006,66(2):239
We propose novel algebraic proof techniques for rewrite systems. Church–Rosser theorems and further fundamental statements that do not mention termination are proved in Kleene algebra. Certain reduction and transformation theorems for termination that depend on abstract commutation, cooperation or simulation properties are proved in an extension with infinite iteration. Benefits of the algebraic approach are simple concise calculational proofs by equational reasoning, connection with automata-based decision procedures and a natural formal semantics for rewriting diagrams. It is therefore especially suited for mechanization and automation. 相似文献
95.
It is shown that NMR/NQR-thermometry on Ga single crystals can serve the need of absolute thermometry in a temperature range from below 20 K to above 1 mK. Thus, the sensitive range includes all phase transition temperatures around 1 mK of solid and fluid
3
He, a necessity for an extension of the
3
He-melting-pressure temperature scale towards lower temperatures. The experiments were performed in magnetic fields of 50 to 200 mT and at temperatures down to 200 K using single rf-pulses. Special care was taken for the orientation of the magnetic field with respect to crystal orientation which was obtained by in-situ pulsed NMR-experiments. It has been shown that in the investigated parameter range nonlinear effects in NMR due to high spin alignment had no significant influence. In pulsed NMR as well as in specific heat experiments it could be shown that spin-spin interactions are only weak in Ga and do not influence nuclear paramagnetism, at least at temperatures above 100 K. The advantages of using Ga instead other elements for population difference thermometry are discussed. 相似文献
96.
97.
By a strategy suggested by E. H. Uhlenhuth et al (1983), Diagnostic and Statistical Manual of Mental Disorders (DSM-III) referenced syndrome classifications were derived on the basis of the Hopkins Symptoms Checklist—42 scores of 1,131 elderly community residents. Overall syndrome prevalence rates were consistent with other epidemiologic data: 3.9% for depression, 1.0% for agoraphobia-panic, 2.6% for other phobia, and 6.9% for anxiety. Prevalence rates reflected expected sex differences and showed an age trend for other phobias. Considerable comorbidity among syndromes was observed. The association of the syndromes with patterns of psychosocial risk factors, prior diagnoses, and medication suggests that some but not all of the identified syndromes reflect clinically relevant classifications. If further developed, syndrome classifications based on self-report scales can provide inexpensive and clinically relevant measures of caseness. Required refinements of this approach are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
98.
Georg Koschek 《Journal of microscopy》1992,168(1):79-84
The suitability of cathodoluminescence (CL) measurements for differentiating between different paint pigments is demonstrated with an example of a combined energy-dispersive X-ray (EDX) and CL analysis of different zinc oxide (ZnO) pigments in a paint fragment where the EDX spectra are virtually identical, but where the CL spectra show significant differences. Consequently, it is possible to distinguish different pigments on the basis of CL spectra and monochromatic CL micrographs. 相似文献
99.
Catalyst substrate foils of the highly oxidation resistant Fe-25Cr-5Al alloy (mass contents in %) with a thickness ranging from 40 to 180 μm have been produced by planar flow casting. The rapidly solidified ribbons showed a monophase ferritic microstructure of columnar grains. The grain size determined over a section parallel to the ribbon wheel side ranged from 5 μm for the thin ribbons (40 μm) to 18 μm for the thicker ones {180 μm). This anisotropic columnar solidification microstructure exhibits a strong <100> fiber texture, with the fiber axis nearly perpendicular to the plane of the ribbon. The position of the maximum in the pole figure was tilted from the center point toward the casting direction. Results of uniaxial tensile tests showed that only the yield stress data of the ribbons in the as-cast condition are reproducible, whereas the ultimate tensile strength and the elongation to failure data show a wide scatter band. The fracture mode exhibits ductile features such as glide bands and dimples. 相似文献
100.
This paper describes a technique for the automatic adaptation of a canonical facial model to data obtained by a 3D laser scanner. The facial model is a B-spline surface with 13×16 control points. We introduce a technique by which this canonical model is fit to the scanned data and that takes into consideration the requirements for the animation of facial expressions. The animation of facial expressions is based on the facial action coding system (FACS). Using B-splines in combination with FACS, we automatically create the impression of a moving skin. To increase the realism of the animation we map textural information onto the B-spline surface. 相似文献