3,256 research outputs found

    Incremental context creation and its effects on semantic query precision

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    The final publication is available at Springer via http://dx.doi.org/10.1007/978-3-642-10543-2_19Proceedings of 4th International Conference on Semantic and Digital Media Technologies, SAMT 2009 Graz, Austria, December 2-4, 2009We briefly describe the results of an experimental study on the incremental creation of context out of the results of targeted queries, and discuss the increase in retrieval precision that results from the incremental enrichment of context.This work was supported in part by Consejería de Educación, Comunidad Autónoma de Madrid, under the grant CCG08-UAM/TIC/4303, Búsqueda basada en contexto como alternativa semántica al modelo ontológico. Simone Santini was in part supported by the Ramón y Cajal initiative of the Ministero de educación y ciencia. Alexandra Dumitrescu was in part supported by the European Social Fund, Universidad Autónoma de Madrid

    The influence of stochasticity, landscape structure and species traits on abundant–centre relationships

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    Species have been commonly hypothesized to have high population densities in geographic areas which correspond to either the centre of the species geographic range or climatic niche (abundant–centre hypothesis). However, there is mixed empirical support for this relationship, and little theoretical underpinning. We simulate a species spreading across a set of replicated artificial landscapes to examine the expected level of support for abundant–centre relationships in geographic and niche space. Species niche constraints were modeled as a single axis which was related directly to population growth rates. We found strong evidence for abundant–centre relationships when populations follow deterministic growth, dispersal is high, environmental noise is absent and intraspecific competition is low. However, the incorporation of ecological realism reduced the detectability of abundant–centre relationships considerably. Our results suggest that even in carefully constructed artificial landscapes designed to demonstrate abundant–centre dynamics, the incorporation of small amounts of demographic stochasticity, environmental heterogeneity or landscape structure can strongly influence the relationship between species population density and distance to species geographic range or niche centre. While some simulated relationships were of comparable strength to common empirical support for abundant–centre relationships, our results suggest that these relationships are expected to be fairly variable and weak

    Economic and demographic issues related to deployment of the Satellite Power System (SPS)

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    Growth in energy consumption stimulated interest in exploitation of renewable sources of electric energy. One technology that was proposed is the Satellite Power System (SPS). Before committing the U.S. to such a large program, the Department of Energy and the National Aeronautics and Space Administration are jointly participating in an SPS Concept Development and Evaluation Program. This white paper on industrial and population relocation is part of the FY 78 preliminary evaluation of related socio-economic issues. Results of four preliminary assessment activities are documented

    Multipole correlations in low-dimensional f-electron systems

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    By using a density matrix renormalization group method, we investigate the ground-state properties of a one-dimensional three-orbital Hubbard model on the basis of a j-j coupling scheme. For B400B_4^0 \ne 0, where B40B_4^0 is a parameter to control cubic crystalline electric field effect, one orbital is itinerant, while other two are localized. Due to the competition between itinerant and localized natures, we obtain orbital ordering pattern which is sensitive to B40B_4^0, leading to a characteristic change of Γ3g\Gamma_{3g} quadrupole state into an incommensurate structure. At B40=0B_4^0 = 0, all the three orbitals are degenerate, but we observe a peak at q=0q = 0 in Γ3g\Gamma_{3g} quadrupole correlation, indicating a ferro-orbital state, and the peak at q=πq = \pi in Γ4u\Gamma_{4u} dipole correlation, suggesting an antiferromagnetic state. We also discuss the effect of Γ4u\Gamma_{4u} octupole on magnetic anisotropy.Comment: 4 pages, 3 figures, Proceedings of ASR-WYP-2005 (September 27-29, 2005, Tokai

    Invariant Form of Hyperfine Interaction with Multipolar Moments - Observation of Octupolar Moments in NpO2_{2} and CeB6_{6} by NMR -

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    The invariant form of the hyperfine interaction between multipolar moments and the nuclear spin is derived, and applied to discuss possibilities to identify the antiferro-octupolar (AFO) moments by NMR experiments. The ordered phase of NpO2_{2} and the phase IV of Ce1x_{1-x}Lax_{x}B6_{6} are studied in detail. Recent 17^{17}O NMR for polycrystalline samples of NpO2_{2} are discussed theoretically from our formulation. The observed feature of the splitting of 17^{17}O NMR spectrum into a sharp line and a broad line, their intensity ratio, and the magnetic field dependence of the shift and of the width can be consistently explained on the basis of the triple \bq AFO ordering model proposed by Paix\~{a}o {\it et. al.} Thus, the present theory shows that the 17^{17}O NMR spectrum gives a strong support to the model. The 4 O sites in the fcc NpO2_2 become inequivalent due to the secondary triple \bq ordering of AF-quadrupoles: one cubic and three non-cubic sites. It turns out that the hyperfine field due to the antiferro-dipole and AFO moments induced by the magnetic field, and the quadrupolar field at non-cubic sites are key ingredients to understand the observed spectrum. The controversial problem of the nature of phase IV in Ce1x_{1-x}Lax_{x}B6_{6} is also studied. It is pointed out that there is a unique feature in the NMR spectra, if the Γ5\Gamma_{5}(Txβ=Tyβ=TzβT^{\beta}_{x}=T^{\beta}_{y}=T^{\beta}_{z}) AFO ordering is realized in Ce1x_{1-x}Lax_{x}B6_{6}. Namely, the hyperfine splitting of a B atom pair on the (1/2,1/2,±u)({1/2},{1/2},\pm u) sites crosses zero on the (11ˉ0)(1\bar{1}0) plane when the magnetic field is rotated around the [001][001] axis.Comment: 22 pages, 2 figure

    The evolution of the AGN content in groups up to z~1

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    Determining the AGN content in structures of different mass/velocity dispersion and comparing them to higher mass/lower redshift analogs is important to understand how the AGN formation process is related to environmental properties. We use our well-tested cluster finding algorithm to identify structures in the GOODS North and South fields, exploiting the available spectroscopic redshifts and accurate photometric redshifts. We identify 9 structures in GOODS-south (presented in a previous paper) and 8 new structures in GOODS-north. We only consider structures where at least 2/3 of the members brighter than M_R=-20 have a spectroscopic redshift. For those group members that coincide with X-ray sources in the 4 and 2 Msec Chandra source catalogs respectively, we determine if the X-ray emission originates from AGN activity or it is related to the galaxies' star-formation activity. We find that the fraction of AGN with Log L_H > 42 erg/s in galaxies with M_R < -20 is on average 6.3+-1.3%, much higher than in lower redshift groups of similar mass and more than double the fraction found in massive clusters at a similarly high redshift. We then explore the spatial distribution of AGN in the structures and find that they preferentially populate the outer regions. The colors of AGN host galaxies in structures tend to be confined to the green valley, thus avoiding the blue cloud and, partially, also the red-sequence, contrary to what happens in the field. We finally compare our results to the predictions of two sets of semi analytic models to investigate the evolution of AGN and evaluate potential triggering and fueling mechanisms. The outcome of this comparison attests the importance of galaxy encounters, not necessarily leading to mergers, as an efficient AGN triggering mechanism. (abridged)Comment: 11 pages, 8 figures, Accepted accepted for publication in A&

    APPLICATIONS OF THE INFRARED THERMOGRAPHY TO THE ASSESSMENT OF HISTORIC BUILDINGS: A CASE STUDY IN PISA

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    Measuring the thermal response of materials in building assessment has a wide range of applications concerning not only the thermophysical aspects, but also the structural ones. The last topic is particularly interesting in the context of historic buildings, where the modern tools for surface temperature measurement are capable of providing many useful information: the masonry texture and the materials detection under the plaster are the fundamentals for the evaluation of the structural behavior and for the selection of the strengthening and restoration criteria. In this regard, the full-field, contactless and real time investigation makes the infrared thermography indispensable. The thermographic technique is taken here into consideration in an emblematic case study
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