2,076 research outputs found
Fund Finder: A case study of database-to-ontology mapping
The mapping between databases and ontologies is a basic problem when trying to "upgrade" deep web content to the semantic web. Our approach suggests the declarative definition of mappings as a way to achieve domain independency and reusability. A specific language (expressive enough to cover some real world mapping situations like lightly structured databases or not 1st normal form ones) is defined for this purpose. Along with this mapping description language, the ODEMapster processor is in charge of carrying out the effective instance data migration. We illustrate this by testing both the mappings definition and processor on a case study
R2O, an extensible and semantically based database-to-ontology mapping language
We present R2O, an extensible and declarative language to describe mappings between relational DB schemas and ontologies implemented in RDF(S) or OWL. R2O provides an extensible set of primitives with welldefined semantics. This language has been conceived expressive enough to cope with complex mapping cases arisen from situations of low similarity between the ontology and the DB models
Non-extensive radiobiology
The expression of survival factors for radiation damaged cells is based on
probabilistic assumptions and experimentally fitted for each tumor, radiation
and conditions. Here we show how the simplest of these radiobiological models
can be derived from the maximum entropy principle of the classical
Boltzmann-Gibbs expression. We extend this derivation using the Tsallis entropy
and a cutoff hypothesis, motivated by clinical observations. A generalization
of the exponential, the logarithm and the product to a non-extensive framework,
provides a simple formula for the survival fraction corresponding to the
application of several radiation doses on a living tissue. The obtained
expression shows a remarkable agreement with the experimental data found in the
literature, also providing a new interpretation of some of the parameters
introduced anew. It is also shown how the presented formalism may has direct
application in radiotherapy treatment optimization through the definition of
the potential effect difference, simply calculated between the tumour and the
surrounding tissue.Comment: 8 pages, 1 figure. Sent to MaxEnt 2010. To be submitted for
publicatio
Integrable systems with BMS Poisson structure and the dynamics of locally flat spacetimes
We construct a hierarchy of integrable systems whose Poisson structure
corresponds to the BMS algebra, and then discuss its description in terms
of the Riemannian geometry of locally flat spacetimes in three dimensions. The
analysis is performed in terms of two-dimensional gauge fields for .
Although the algebra is not semisimple, the formulation can be carried out \`a
la Drinfeld-Sokolov because it admits a nondegenerate invariant bilinear
metric. The hierarchy turns out to be bi-Hamiltonian, labeled by a nonnegative
integer , and defined through a suitable generalization of the Gelfand-Dikii
polynomials. The symmetries of the hierarchy are explicitly found. For , the corresponding conserved charges span an infinite-dimensional Abelian
algebra without central extensions, and they are in involution; while in the
case of , they generate the BMS algebra. In the special case of
, by virtue of a suitable field redefinition and time scaling, the field
equations are shown to be equivalent to a specific type of the Hirota-Satsuma
coupled KdV systems. For , the hierarchy also includes the so-called
perturbed KdV equations as a particular case. A wide class of analytic
solutions is also explicitly constructed for a generic value of .
Remarkably, the dynamics can be fully geometrized so as to describe the
evolution of spacelike surfaces embedded in locally flat spacetimes. Indeed,
General Relativity in 3D can be endowed with a suitable set of boundary
conditions, so that the Einstein equations precisely reduce to the ones of the
hierarchy aforementioned. The symmetries of the integrable systems then arise
as diffeomorphisms that preserve the asymptotic form of the spacetime metric,
and therefore, they become Noetherian. The infinite set of conserved charges is
recovered from the corresponding surface integrals in the canonical approach.Comment: 34 pages, 2 figure
Evaluación de la distribución del Gasto Público en un marco Post-Keynesiano para una economía abierta
Un creciente peso económico de los gobiernos a lo largo del mundo junto con una relación negativa entre los niveles de gasto público y el ritmo de crecimiento, abren el interrogante sobre cuál debe ser el papel óptimo del Estado. Desde una óptica postkeynesiana se explora la posibilidad de que la distribución que realice el gobierno de su gasto pueda explicar esta relación negativa al generar dinámicas insostenibles en el largo plazo o que aun pareciendo positivas puedan estar reduciendo el potencial futuro dado un efecto negativo sobre la acumulación de capital físico y humano. Así, para eliminar el efecto negativo de la intervención estatal, bastaría con reestructurar el gasto público, privilegiando aquellas partidas que afecten de forma positiva la productividad al tiempo que generan demanda efectiva en el corto plazo. / Abstract. A heavy economic growth of the governments throughout the world goes hand in hand with a negative relationship between the standard of public spending and the growth rate, raising the question what the ideal role of the state is. From the post-Keynesian point of view the possibility has to be investigated that governments budget spending could explain this negative relationship by generating a long term unsustainable dynamic or even though it appears positive it could be reducing the future potential therefore resulting in a negative effect over the accumulation of physical and human capital. Thus, to eliminate the negative effect of state intervention, it would be sufficient to restructure public spending, favoring those parties that affect in a positive way productivity while generating demand effectively short term.Maestrí
CMOS SPADs selection, modeling and characterization towards image sensors implementation
The selection, modeling and characterization of Single Photon Avalanche Diodes (SPADs) are presented. Working with the standard 180nm UMC CMOS process, different SPAD structures are proposed in combination with several quenching circuits in order to compare their relative performances. Various configurations for the active region and the prevention of the premature edge breakdown are tested, looking for a miniaturization of the devices to implement image sensor arrays without loses in their performance
Financiamiento especulativo de la vivienda en Colombia: un análisis de la dinámica de los precios, 2000-2016
This paper studies the dynamics of housing prices in Colombia from 2000 to 2016. The non-conventional theoretical foundations for price determination are presented, along with two quantitative strategies: 1) a descriptive study of the market and the possible financial fragility that has allowed the increase in prices of new housing; and 2) a VEC econometric model that captures the short and long term price determinants. The paper concludes that the dynamics of housing prices is influenced by mortgage loans and construction costs, and has a strong long-term relationship between current and previous behavior of prices, made evident in speculative financial scenarios.O presente trabalho estuda a dinâmica dos preços da moradia na Colômbia no período de 2000 a 2016. Apresentam-se os fundamentos teóricos não convencionais para a determinação do preço, juntamente com duas estratégias quantitativas: 1) um estudo descritivo do mercado e da possível fragilidade financeira que permitiu o aumento dos preços de imóveis novos, e 2) um modelo econométrico VEC que captura os determinantes de curto e longo prazo do preço. Conclui-se que a dinâmica do preço da moradia é influenciada pelo crédito hipotecário e pelos custos de construção, além de apresentar uma forte relação de longo prazo entre o comportamento atual e prévio dos preços, evidentes nos cenários financeiros especulativos.El presente trabajo estudia la dinámica de los precios de la vivienda en Colombia para el periodo 2000 a 2016. Se presentan los fundamentos teóricos no-convencionales para la determinación del precio, junto con dos estrategias cuantitativas: 1) un estudio descriptivo del mercado y la posible fragilidad financiera que ha permitido el incremento de los precios de la vivienda nueva; y 2) un modelo econométrico VEC que captura los determinantes de corto y largo plazo del precio. Se concluye que la dinámica del precio de la vivienda está influenciada por el crédito hipotecario y los costos de construcción, y presenta una fuerte relación de largo plazo entre el comportamiento actual y previo de los precios, evidentes en los escenarios financieros especulativos
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