22,009 research outputs found
Contrary-to-duties constraints: from UML to relational model
WOS:000261373900033Sometimes, because of an atypical Situation, ail important mandatory association between classes in a UML Class Diagram Must be replaced by all optional one. That semantic and functional impoverishment happens because the mandatory constraint must have a boolean value. In this paper we analyze the use Of soft constraints in the UML Class Diagram, and their automatic repercussion in the corresponding Relational Model. The soft (deontic) constraints allow the formal representation of requirements, which ideally should always be fulfilled, but can be violated in atypical situations. In this paper we enrich a previous deontic approach, by introducing the ability to explicitly represent the so called Contrary-To-Duties requirements, i.e.. domain integrity requirements that emerge as a consequence of an unfulfilled mandatory constraint. We Support our approach with the UML/OCL language.info:eu-repo/semantics/acceptedVersio
Value-at-Risk and Tsallis statistics: risk analysis of the aerospace sector
In this study, we analyze the aerospace stocks prices in order to
characterize the sector behavior. The data analyzed cover the period from
January 1987 to April 1999. We present a new index for the aerospace sector and
we investigate the statistical characteristics of this index. Our results show
that this index is well described by Tsallis distribution. We explore this
result and modify the standard Value-at-Risk (VaR), financial risk assessment
methodology in order to reflect an asset which obeys Tsallis non-extensive
statistics.Comment: 10 pages, 4 figures, 1 table, to appear in Physica
Shear-melting of a hexagonal columnar crystal by proliferation of dislocations
A hexagonal columnar crystal undergoes a shear-melting transition above a
critical shear rate or stress. We combine the analysis of the shear-thinning
regime below the melting with that of synchrotron X-ray scattering data under
shear and propose the melting to be due to a proliferation of dislocations,
whose density is determined by both techniques to vary as a power law of the
shear rate with a 2/3 exponent, as expected for a creep model of crystalline
solids. Moreover, our data suggest the existence under shear of a line hexatic
phase, between the columnar crystal and the liquid phase
An intrinsic state for an extended version of the interacting boson model
An intrinsic-state formalism for IBM-4 is presented. A basis of deformed
bosons is introduced which allows the construction of a general trial wave
function which has Wigner's spin-isospin SU(4) symmetry as a particular limit.
Intrinsic-state calculations are compared with exact ones showing good
agreement.Comment: 12 pages, TeX (ReVTeX). Content changed. Accepted in Phys. Rev.
BEC-BCS crossover in a cold and magnetized two color NJL model
The BEC-BCS crossover for a NJL model with diquark interactions is studied in
the presence of an external magnetic field. Particular attention is paid to
different regularization schemes used in the literature. A thorough comparison
of results is performed for the case of a cold and magnetized two-color NJL
model. According to our results, the critical chemical potential for the BEC
transition exhibits a clear inverse magnetic catalysis effect for magnetic
fields in the range . As for the BEC-BCS
crossover, the corresponding critical chemical potential is very weakly
sensitive to magnetic fields up to , showing a much smaller
inverse magnetic catalysis as compared to the BEC transition, and displays a
strong magnetic catalysis from this point on.Comment: 15 pages, 8 figures; v2 PRD versio
The type N Karlhede bound is sharp
We present a family of four-dimensional Lorentzian manifolds whose invariant
classification requires the seventh covariant derivative of the curvature
tensor. The spacetimes in questions are null radiation, type N solutions on an
anti-de Sitter background. The large order of the bound is due to the fact that
these spacetimes are properly , i.e., curvature homogeneous of order 2
but non-homogeneous. This means that tetrad components of are constant, and that essential coordinates first appear as
components of . Covariant derivatives of orders 4,5,6 yield one
additional invariant each, and is needed for invariant
classification. Thus, our class proves that the bound of 7 on the order of the
covariant derivative, first established by Karlhede, is sharp. Our finding
corrects an outstanding assertion that invariant classification of
four-dimensional Lorentzian manifolds requires at most .Comment: 7 pages, typos corrected, added citation and acknowledgemen
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Controllable direction of liquid jets generated by thermocavitation within a droplet.
A high-velocity fluid stream ejected from an orifice or nozzle is a common mechanism to produce liquid jets in inkjet printers or to produce sprays among other applications. In the present research, we show the generation of liquid jets of controllable direction produced within a sessile water droplet by thermocavitation. The jets are driven by an acoustic shock wave emitted by the collapse of a hemispherical vapor bubble at the liquid-solid/substrate interface. The generated shock wave is reflected at the liquid-air interface due to acoustic impedance mismatch generating multiple reflections inside the droplet. During each reflection, a force is exerted on the interface driving the jets. Depending on the position of the generation of the bubble within the droplet, the mechanical energy of the shock wave is focused on different regions at the liquid-air interface, ejecting cylindrical liquid jets at different angles. The ejected jet angle dependence is explained by a simple ray tracing model of the propagation of the acoustic shock wave inside the droplet
Bioeletricidade no setor sucroalcooleiro paulista: participação no mercado de carbono, perspectivas e sustentabilidade.
bitstream/item/12264/1/documentos_78.pd
First report of Puccinia thaliae causing rust on Canna spp. in Europe
Disease Notesinfo:eu-repo/semantics/publishedVersio
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