Matrices con inversa positiva

El objeto de este trabajo es presentar un análisis de las matrices reales con inversa positiva. Es una clase de matrices que contiene a las M-matrices, de las que heredan algunas de sus numerosas aplicaciones y de sus propiedades. Presentamos algunos ejemplos de matrices inversa positiva, que aparecen en problemas de discretización, de factorización de matrices, etc. Hacemos un estudio de las propiedades hereditarias de esta clase de matrices, prestando especial atenci´on a la suma sub-directa, y establecemos relaciones entre estas matrices y otras clases de matrices como las totalmente no negativas, las matrices monótonas, etc

El conflicto del Líbano

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Los sistemas de iluminación de grandes edificios desde la visión de la mantenibilidad y la eficiencia energetica

En este trabajo se estudian las posibilidades técnicas de mejora del ahorro energético en la iluminación de edificios de gran escala. Para ello en primer lugar se analiza la reglamentación que afecta a las instalaciones de iluminación en edificación, después se estudia todo lo relativo al mantenimiento de dichas instalaciones, tras lo cual se hace un análisis de los sistemas de eficiencia energética aplicables. Partiendo de los datos obtenidos, se estudia un caso práctico centrado en el Colegio de los Dominicos de Valencia, y por último se establecen los resultados y conclusiones del estudio.Sánchez Rodríguez, JM. (2013). Los sistemas de iluminación de grandes edificios desde la visión de la mantenibilidad y la eficiencia energetica. http://hdl.handle.net/10251/33501.Archivo delegad

An Approach to the Multivectorial Apparent Power in Terms of a Generalized Poynting Multivector

The purpose of this paper is to explain an exact derivation of apparent power in n-sinusoidal operation founded on electromagnetic theory, until now unexplained by simple mathematical models. The aim is to explore a new tool for a rigorous mathematical and physical analysis of the power equation from the Poynting Vector (PV) concept. A powerful mathematical structure is necessary and Geometric Algebra offers such a characteristic. In this sense, PV has been reformulated from a new Multivectorial Euclidean Vector Space structure (CGn-R3) to obtain a Generalized Poynting Multivector ( ~ S). Consequently, from ~ S, a suitable multivectorial form ( ~ P and ~D) of the Poynting Vector corresponds to each component of apparent power. In particular, this framework is essential for the clari¯cation of the connection between a Complementary Poynting Multivector (~D) and the power contribution due to cross-frequency products. A simple application example is presented as an illustration of the proposed power multivector analysis

Considerations on the non-active power using geometric algebra

Several approaches have been developed to define the non-active power concept under nonsinusoidal situations in electrical systems. Nevertheless, these contributions do not provide a complete and satisfactory solution to the non-active power reversibility between frequency domain and time domain. This paper presents a non-active power multivector concept, based on an original vector space frequency-domain approach that bridges the gap between both domains. The suggested correspondence can provide a convenient descriptive language to reconcile Fryze’s instantaneous non-active power with Budeanu´s deactive-power

Data-independent Random Projections from the feature-map of the homogeneous polynomial kernel of degree two

[EN] This paper presents a novel non-linear extension of the Random Projection method based on the degree-2 homogeneous polynomial kernel. Our algorithm is able to implicitly map data points to the high-dimensional feature space of that kernel and from there perform a Random Projection to an Euclidean space of the desired dimensionality. Pairwise distances between data points in the kernel feature space are approximately preserved in the resulting representation. As opposed to previous kernelized Random Projection versions, our method is data-independent and preserves much of the computational simplicity of the original algorithm. This is achieved by focusing on a specific kernel function, what allowed us to analyze the effect of its associated feature mapping in the distribution of the Random Projection hyperplanes. Finally, we present empirical evidence that the proposed method outperforms alternative approaches in terms of pairwise distance preservation, while being significantly more efficient. Also, we show how our method can be used to approximate the accuracy of non-linear classifiers with efficient linear classifiers in some datasets

Compact bilinear pooling via kernelized random projection for fine-grained image categorization on low computational power devices

[EN]Bilinear pooling is one of the most popular and effective methods for fine-grained image recognition. However, a major drawback of Bilinear pooling is the dimensionality of the resulting descriptors, which typically consist of several hundred thousand features. Even when generating the descriptor is tractable, its dimension makes any subsequent operations impractical and often results in huge computational and storage costs. We introduce a novel method to efficiently reduce the dimension of bilinear pooling descriptors by performing a Random Projection. Conveniently, this is achieved without ever computing the high-dimensional descriptor explicitly. Our experimental results show that our method outperforms existing compact bilinear pooling algorithms in most cases, while running faster on low computational power devices, where efficient extensions of bilinear pooling are most useful

Psychological elements explaining the consumer's adoption and use of a website recommendation system: A theoretical framework proposal

The purpose of this paper is to understand, with an emphasis on the psychological perspective of the research problem, the consumer's adoption and use of a certain web site recommendation system as well as the main psychological outcomes involved. The approach takes the form of theoretical modelling. Findings: A conceptual model is proposed and discussed. A total of 20 research propositions are theoretically analyzed and justified. Research limitations/implications: The theoretical discussion developed here is not empirically validated. This represents an opportunity for future research. Practical implications: The ideas extracted from the discussion of the conceptual model should be a help for recommendation systems designers and web site managers, so that they may be more aware, when working with such systems, of the psychological process consumers undergo when interacting with them. In this regard, numerous practical reflections and suggestions are presented

The microbiome of the uropygial secretion in hoopoes is shaped along the nesting phase

Microbial symbiont acquisition by hosts may determine the effectiveness of the mutualistic relationships. A mix of vertical and horizontal transmission may be advantageous for hosts by allowing plastic changes of microbial communities depending on environmental conditions. Plasticity is well known for gut microbiota but is poorly understood for other symbionts of wild animals. We here explore the importance of environmental conditions experienced by nestling hoopoes (Upupa epops) during the late nesting phase determining microbiota in their uropygial gland. In cross-fostering experiments of 8 days old nestlings, “sibling-sibling” and “mother-offspring” comparisons were used to explore whether the bacterial community naturally established in the uropygial gland of nestlings could change depending on experimental environmental conditions (i.e., new nest environment). We found that the final microbiome of nestlings was mainly explained by nest of origin. Moreover, cross-fostered nestlings were more similar to their siblings and mothers than to their stepsiblings and stepmothers. We also detected a significant effect of nest of rearing, suggesting that nestling hoopoes acquire most bacterial symbionts during the first days of life but that the microbiome is dynamic and can be modified along the nestling period depending on environmental conditions. Estimated effects of nest of rearing, but also most of those of nest of origin are associated to environmental characteristics of nests, which are extended phenotypes of parents. Thus, natural selection may favor the acquisition of appropriated microbial symbionts for particular environmental conditions found in nests.Support by funding was provided by Spanish Ministerio de Economía y Competitividad, European funds (FEDER) (CGL2013-48193-C3-1-P, CGL2013-48193-C3-2-P), and Junta de Andalucía (P09-RNM-4557). AM-G had a predoctoral grant from the Junta de Andalucía (P09-RNM-4557).Peer reviewe