1,939 research outputs found
Designing data warehouses for geographic OLAP querying by using MDA
Data aggregation in Geographic Information Systems (GIS) is a desirable feature, spatial data are integrated in OLAP engines for this purpose. However, the development and operation of those systems is still a complex task due to methodologies followed. There are some ad hoc solutions that deal only with isolated aspects and do not provide developer and analyst with an intuitive, integrated and standard framework for designing all relevant parts. To overcome these problems, we have defined a model driven approach to accomplish Geographic Data Warehouse (GDW) development. Then, we have defined a data model required to implement and query spatial data. Its modeling is defined and implemented by using an extension of UML metamodel and it is also formalized by using OCL language. In addition, the proposal has been verified against a example scenario with sample data sets. For this purpose, we have accomplished a developing tool based on Eclipse platform and MDA standard. The great advantage of this solution is that developers can directly include spatial data at conceptual level, while decision makers can also conceptually make geographic queries without being aware of logical details.This work has been partially supported by the ESPIA project (TIN2007-67078) from the Spanish Ministry of Education and Science and by the QUASIMODO project (PAC08-0157-0668) from the Castilla-La Mancha Ministry of Education and Science (Spain). Octavio Glorio is funded by the University of Alicante under the 11th Latin American grant program
Strain dependence of bonding and hybridization across the metal-insulator transition of VO2
Soft x-ray spectroscopy is used to investigate the strain dependence of the
metal-insulator transition of VO2. Changes in the strength of the V 3d - O 2p
hybridization are observed across the transition, and are linked to the
structural distortion. Furthermore, although the V-V dimerization is
well-described by dynamical mean-field theory, the V-O hybridization is found
to have an unexpectedly strong dependence on strain that is not predicted by
band theory, emphasizing the relevance of the O ion to the physics of VO2
Surface plasmon polariton modes in a single-crystal Au nanoresonator fabricated using focused-ion-beam milling
We use focused-ion-beam milling of a single-crystal Au surface to fabricate a
590-nm-long linear ridge that acts as a surface plasmon nanoresonator.
Cathodoluminescence imaging spectroscopy is then used to excite and image
surface plasmons on the ridge. Principal component analysis reveals distinct
plasmonic modes, which proves confinement of surface-plasmon oscillations to
the ridge. Boundary-element-method calculations confirm that a linear ridge is
able to support highly-localized surface-plasmon modes (mode diameter < 100
nm). The results demonstrate that focused-ion-beam milling can be used in rapid
prototyping of nanoscale single-crystal plasmonic components.Comment: 4 pages, 4 figure
Magnetism and unconventional superconductivity in CeMIn heavy-fermion crystals
We review magnetic, superconducting and non-Fermi-liquid properties of the
structurally layered heavy-fermion compounds CeMIn (M=Co, Rh,
Ir). These properties suggest d-wave superconductivity and proximity to an
antiferromagetic quantum-critical point.Comment: submitted 23rd International Conference on Low Temperature Physics
(LT-23), Aug. 200
Modifying the Symbolic Aggregate Approximation Method to Capture Segment Trend Information
The Symbolic Aggregate approXimation (SAX) is a very popular symbolic
dimensionality reduction technique of time series data, as it has several
advantages over other dimensionality reduction techniques. One of its major
advantages is its efficiency, as it uses precomputed distances. The other main
advantage is that in SAX the distance measure defined on the reduced space
lower bounds the distance measure defined on the original space. This enables
SAX to return exact results in query-by-content tasks. Yet SAX has an inherent
drawback, which is its inability to capture segment trend information. Several
researchers have attempted to enhance SAX by proposing modifications to include
trend information. However, this comes at the expense of giving up on one or
more of the advantages of SAX. In this paper we investigate three modifications
of SAX to add trend capturing ability to it. These modifications retain the
same features of SAX in terms of simplicity, efficiency, as well as the exact
results it returns. They are simple procedures based on a different
segmentation of the time series than that used in classic-SAX. We test the
performance of these three modifications on 45 time series datasets of
different sizes, dimensions, and nature, on a classification task and we
compare it to that of classic-SAX. The results we obtained show that one of
these modifications manages to outperform classic-SAX and that another one
slightly gives better results than classic-SAX.Comment: International Conference on Modeling Decisions for Artificial
Intelligence - MDAI 2020: Modeling Decisions for Artificial Intelligence pp
230-23
Anisotropy of Thermal Conductivity and Possible Signature of the Fulde-Ferrell-Larkin-Ovchinnikov state in CeCoIn_5
We have measured the thermal conductivity of the heavy-fermion superconductor
CeCoIn_5 in the vicinity of the upper critical field, with the magnetic field
perpendicular to the c axis. Thermal conductivity displays a discontinuous jump
at the superconducting phase boundary below critical temperature T_0 ~ 1 K,
indicating a change from a second to first order transition and confirming the
recent results of specific heat measurements on CeCoIn_5. In addition, the
thermal conductivity data as a function of field display a kink at a field H_k
below the superconducting critical field, which closely coincides with the
recently discovered anomaly in specific heat, tentatively identified with the
appearance of the spatially inhomogeneous Fulde-Ferrell-Larkin-Ovchinnikov
(FFLO) superconducting state. Our results indicate that the thermal
conductivity is enhanced within the FFLO state, and call for further
theoretical investigations of the order parameter's real space structure (and,
in particular, the structure of vortices) and of the thermal transport within
the inhomogeneous FFLO state.Comment: 19 pages, 6 figures, submitted to Prhys. Rev.
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