38,130 research outputs found
Endurant Types in Ontology-Driven Conceptual Modeling: Towards OntoUML 2.0
For over a decade now, a community of researchers has contributed
to the development of the Unified Foundational Ontology (UFO)
- aimed at providing foundations for all major conceptual modeling constructs.
This ontology has led to the development of an Ontology-Driven
Conceptual Modeling language dubbed OntoUML, reflecting the ontological
micro-theories comprising UFO. Over the years, UFO and OntoUML
have been successfully employed in a number of academic, industrial and
governmental settings to create conceptual models in a variety of different
domains. These experiences have pointed out to opportunities of
improvement not only to the language itself but also to its underlying
theory. In this paper, we take the first step in that direction by revising
the theory of types in UFO in response to empirical evidence. The
new version of this theory shows that many of the meta-types present
in OntoUML (differentiating Kinds, Roles, Phases, Mixins, etc.) should
be considered not as restricted to Substantial types but instead should
be applied to model Endurant Types in general, including Relator types,
Quality types and Mode types. We also contribute a formal characterization
of this fragment of the theory, which is then used to advance a
metamodel for OntoUML 2.0. Finally, we propose a computational support
tool implementing this updated metamodel
X-ray powder diffraction of high-absorption materials at the XRD1 beamline off the best conditions: Application to (Gd,Nd)5Si4 compounds
Representative compounds of the new family of magnetic materials Gd5-xNdxSi4
were analyzed by X-ray diffraction at the XRD1 beamline at LNLS. To reduce
X-ray absorption, thin layers of the powder samples were mounted outside the
capillaries and measured in Debye-Scherrer geometry as usual. The X-ray
diffraction analyses and the magnetometry results indicate that the behavior of
the magnetic transition temperature as a function of Nd content may be directly
related to the average of the four smallest interatomic distances between
different rare earth sites of the majority phase of each compound. The quality
and consistency of the results show that the XRD1 beamline is able to perform
satisfactory X-ray diffraction experiments on high-absorption materials even
off the best conditions.Comment: 12 pages, 3 figures, 3 table
White dwarfs with a surface electrical charge distribution: Equilibrium and stability
The equilibrium configuration and the radial stability of white dwarfs
composed of charged perfect fluid are investigated. These cases are analyzed
through the results obtained from the solution of the hydrostatic equilibrium
equation. We regard that the fluid pressure and the fluid energy density follow
the relation of a fully degenerate electron gas. For the electric charge
distribution in the object, we consider that it is centralized only close to
the white dwarfs' surfaces. We obtain larger and more massive white dwarfs when
the total electric charge is increased. To appreciate the effects of the
electric charge in the structure of the star, we found that it must be in the
order of with which the electric field is about
. For white dwarfs with electric fields close to the
Schwinger limit, we obtain masses around . We also found that in
a system constituted by charged static equilibrium configurations, the maximum
mass point found on it marks the onset of the instability. This indicates that
the necessary and sufficient conditions to recognize regions constituted by
stable and unstable equilibrium configurations against small radial
perturbations are respectively and .Comment: This is a preprint. The original paper will be published in EPJ
INEFFECTIVE CONTROLS ON CAPITAL INFLOWS UNDER SOPHISTICATED FINANCIAL MARKETS: BRAZIL IN THE NINETIES
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