Evaluation of recommender systems in streaming environments

Evaluation of recommender systems is typically done with finite datasets. This means that conventional evaluation methodologies are only applicable in offline experiments, where data and models are stationary. However, in real world systems, user feedback is continuously generated, at unpredictable rates. Given this setting, one important issue is how to evaluate algorithms in such a streaming data environment. In this paper we propose a prequential evaluation protocol for recommender systems, suitable for streaming data environments, but also applicable in stationary settings. Using this protocol we are able to monitor the evolution of algorithms' accuracy over time. Furthermore, we are able to perform reliable comparative assessments of algorithms by computing significance tests over a sliding window. We argue that besides being suitable for streaming data, prequential evaluation allows the detection of phenomena that would otherwise remain unnoticed in the evaluation of both offline and online recommender systems.Comment: Workshop on 'Recommender Systems Evaluation: Dimensions and Design' (REDD 2014), held in conjunction with RecSys 2014. October 10, 2014, Silicon Valley, United State

El manejo de grandes parques urbanos en la ciudad: apuntes sobre las políticas públicas ambientales: el Estero el Salado en Puerto Vallarta

El problema de la gestión de los espacios naturales en ciudades dista mucho de estar resuelto. Por ello, en primer término se tiene que hacer un esfuerzo referente a su interpretación y conceptualización, ya que al respecto predominan los trabajos con un enfoque normativo y los estudios de corte arquitectónico, los cuales ponen especial acento en su funcionalidad, estética y los servicios recreativos y culturales que estos espacios proporcionan. Sin embargo, poco exploran acerca de las formas de gestión, acceso y sus vinculaciones con el resto del entorno urbano. En este sentido, aquí importa abordar la problemática de los grandes parques urbanos en las metrópolis a partir de la teoría de los bienes públicos y de la política pública. Se parte de dos premisas centrales que son los hilos conductores de este trabajo: 1. Considerar que los parques urbanos son un conjunto de recursos renovables limitados que requieren de una atención sistemática y especializada por parte de las autoridades responsables, a fin de garantizar su desarrollo sustentable; y 2. Dada la importancia que los espacios de valor ambiental tienen para la ciudad, ponen de manifiesto la necesidad de conciliar los esquemas de gestión de la oferta recreativo-cultural con los de orden ambiental. Asimismo, detrás de estas premisas subyacen las siguientes interrogantes: ¿cómo garantizar la sustentabilidad de los parques urbanos? ¿Qué sucede cuando los parques son de libre acceso? ¿Quiénes deben internalizar los costos y recibir los beneficios por su mantenimiento cuando estos espacios prestan servicios a escala metropolitana? ¿Es posible que un agente privado pueda hacerse cargo de estos espacios y garantizar su funcionamiento sin exclusión para el beneficio de todos? ¿Pueden instrumentarse acciones eficaces para el incremento de espacios verdes a fin de contrarrestar la escasez de los bienes públicos ambientales? En términos generales se abordan cinco temas: El primero hace énfasis en el valor estratégico que hoy tienen los parques urbanos para el posicionamiento de las ciudades y su importancia para la integración social y reforzamiento identitario de una comunidad en el contexto de la globalización. El segundo apartado se refiere a los grandes parques urbanos considerados como un bien público ambiental y el problema de la acción colectiva en el suministro de éstos, así como el papel que juegan en el aseguramiento de la sustentabilidad en contextos urbanos. De igual modo se examina el asunto de las externalidades a la que están sujetos estos espacios naturales y el carácter distributivo de los programas que las autoridades implantan para corregirlas. El tercer tema aborda el diseño de políticas públicas y los programas de manejo integrales de los parques urbanos, a fin de mantener e incrementar sus potencialidades bióticas y físicas. El cuarto tema, propone el análisis de un caso práctico a partir del rescate del “Estero el Salado”. Finalmente, en el quinto apartado de presentan las conclusiones derivadas de este articulo.Peer Reviewe

INFRA-ESTRUTURA DIGITAL E INTELIGÊNCIA DOS TERRITÓRIOS EM PORTUGAL: A INTERNET, A WORLD WIDE WEB E AS EMPRESAS

Os territórios têm vindo a assumir nos anos mais recentes novas competências e desafios no quadro da valorização das novas tecnologias e da centralidade dos factores intangíveis essenciais para a criação de vantagens competitivas e para a qualificação dos territórios. A Internet tem-se tornado um instrumento privilegiado na disseminação de informação, na partilha de conhecimento e na interactividade, criando novas oportunidades para os agentes do sistema de conhecimento e inovação e da base produtiva, passando as estratégias empresariais cada vez mais pela economia digital e pela utilização de novos instrumentos digitais. Neste sentido, é importante que se compreenda a plataforma digital em Portugal traduzida pelo reflexo dos websites no território e sectores a que se encontram “ligados”. A determinação de potenciais Web e a correlação com o contexto territorial traduzirá a digitalidade dos territórios e as potencialidades no seio da nova economia digital e do conhecimento

Enhancing precision in process conformance: stability, confidence and severity

Process Conformance is becoming a crucial area due to the changing nature of processes within an Information System. By confronting specifications against system executions (the main problem tackled in process conformance), both system bugs and obsolete/incorrect specifications can be revealed. This paper presents novel techniques to enrich the process conformance analysis for the precision dimension. The new features of the metric proposed in this paper provides a complete view of the precision between a log and a model. The techniques have been implemented as a plug-in in an open-source Process Mining platform and experimental results witnessing both the theory and the goals of this work are presented.Postprint (published version

Fiscal Decentralization and Public R&D Policy: A Country Panel Analysis

This paper presents a first analysis of the potential link between the level of fiscal decentralization of a country and its public investment in innovation. We present a theoretical model where a ‘benevolent government’ invests in R&D aiming at maximizing net income, and R&D results are subject to interregional knowledge spillovers. The model predicts that decentralization leads to a lower level of public spending on innovation, and to a lower share of basic research in the government R&D budget. These hypotheses are empirically tested using country aggregate data. The results provide empirical support to the mentioned hypotheses, as we find evidence that higher levels of both expenditure and revenue decentralization are associated with a lower intensity of basic research in public R&D and with a lower level of R&D spending. The strength of the evidence, however, is weakened by the small sample size and shortcomings of the indicators used in the analysis

Áreas metropolitanas, competencias, capacidades y procesos, hacia una gobernabilidad y gobernanza eficaz; la Bahía de Banderas, México

Las transformaciones económicas de las últimas dos décadas han traído como consecuencia nuevos y profundos procesos de reorganización territorial, que implican desde nuevos patrones de localización de la actividad urbana, hasta la aparición de cambios significativos en el papel de las áreas metropolitanas. Dentro de este marco, todo supone que el crecimiento de las ciudades latinoamericanas está respondiendo al fenómeno del “policentrismo” caracterizado por la aparición de distritos territoriales habilitados por la inversión privada en un protagonismo creciente y abierto, manteniendo la dinámica concentradora (tanto productiva como demográfica) y su crecimiento en expansión, en donde quizá, el rasgo más característico sea la conformación de un esquema multinuclear. Un planteamiento policéntrico de este tipo en el interior de las áreas metropolitanas también necesitará una gobernanza metropolitana eficaz. Este artículo examina las competencias, capacidades y proceso necesarios para una ordenación y desarrollo del territorio eficaces a nivel metropolitano, y qué modelos de gobernanza metropolitana podrían considerarse para lograrlos, se analiza el caso de Bahía de banderas, México.The economic transformations of the last two decades have resulted in new and profound processes of territorial reorganization, involving from new location patterns of urban activity, until the appearance of significant changes in the role of metropolitan areas. Within this framework, all assumed that the growth of Latin American cities are responding to the phenomenon of "polycentrism" characterized by the emergence of territorial districts authorized by private investment and open a growing role, maintaining the dynamic concentrator (both productive and demographic) and expanding its growth, where perhaps the most characteristic feature is the formation of a multinuclear scheme. A polycentric approach of this type within metropolitan areas will also need an effective metropolitan governance. This article examines the skills, capabilities and management processes necessary for the effective development of the territory and the metropolitan level, and metropolitan governance models which could be considered to achieve, he examines the case of Bahía de Banderas, México.Peer Reviewe

Effective torsional strength of axially restricted RC beams

In a previous study, design charts where proposed to help the torsional design of axially restricted reinforced concrete (RC) beams with squared cross section. In this article, new design charts are proposed to cover RC beams with rectangular cross section. The influence of the height to width ratio of the cross section on the behavior of RC beams under torsion is firstly shown by using theoretical and experimental results. Next, the effective torsional strength of a reference RC beam is computed for several values and combinations of the study variables, namely: height to width ratio of the cross section, concrete compressive strength, torsional reinforcement ratio and level of the axial restraint. To compute the torsional strength, the modified Variable Angle Truss Model for axially restricted RC beams is used. Then, an extensive parametric analysis based on multivariable and nonlinear correlation analysis is performed to obtain nonlinear regression equations which allow to build the new design charts. These charts allow to correct the torsional strength in order to consider the favourable influence of the compressive axial stress that arises from the axial restraint.info:eu-repo/semantics/publishedVersio

Regulation of cardiac cell fate by microRNAs : implications for heart regeneration

© 2014 by the authors; licensee MDPI, Basel, SwitzerlandmicroRNAs are post-transcriptional regulators of gene expression that have been shown to be central players in the establishment of cellular programs, often acting as switches that control the choice between proliferation and differentiation during development and in adult tissues. The heart develops from two small patches of cells in the mesoderm, the heart fields, which originate the different cardiac cell types, including cardiomyocytes, vascular smooth muscle and endothelial cells. These progenitors proliferate and differentiate to establish a highly connected three-dimensional structure, involving a robust succession of gene expression programs strongly influenced by microRNAs. Although the mammalian heart has conventionally been viewed as a post-mitotic organ, cardiac cells have recently been shown to display some regenerative potential, which is nonetheless insufficient to regenerate heart lesions, in contrast with other vertebrates like the zebrafish. Both the proliferation of adult cardiac stem cells and the ability of cardiomyocytes to re-enter the cell cycle have been proposed to sustain these regenerative processes. Here we review the role of microRNAs in the control of stem cell and cardiomyocyte dependent cardiac regeneration processes, and discuss potential applications for the treatment of cardiac injury.info:eu-repo/semantics/publishedVersio