Time-series Modelling, Stationarity and Bayesian Nonparametric Methods

In this paper we introduce two general non-parametric first-order stationary time-series models for which marginal (invariant) and transition distributions are expressed as infinite-dimensional mixtures. That feature makes them the first Bayesian stationary fully non-parametric models developed so far. We draw on the discussion of using stationary models in practice, as a motivation, and advocate the view that flexible (non-parametric) stationary models might be a source for reliable inferences and predictions. It will be noticed that our models adequately fit in the Bayesian inference framework due to a suitable representation theorem. A stationary scale-mixture model is developed as a particular case along with a computational strategy for posterior inference and predictions. The usefulness of that model is illustrated with the analysis of Euro/USD exchange rate log-returns.Stationarity, Markov processes, Dynamic mixture models, Random probability measures, Conditional random probability measures, Latent processes.

Automatic Metro Map Layout Using Multicriteria Optimization

This paper describes an automatic mechanism for drawing metro maps. We apply multicriteria optimization to find effective placement of stations with a good line layout and to label the map unambiguously. A number of metrics are defined, which are used in a weighted sum to find a fitness value for a layout of the map. A hill climbing optimizer is used to reduce the fitness value, and find improved map layouts. To avoid local minima, we apply clustering techniques to the map the hill climber moves both stations and clusters when finding improved layouts. We show the method applied to a number of metro maps, and describe an empirical study that provides some quantitative evidence that automatically-drawn metro maps can help users to find routes more efficiently than either published maps or undistorted maps. Moreover, we found that, in these cases, study subjects indicate a preference for automatically-drawn maps over the alternatives

Tourism SMEs in a Digital Environment: Literature Review

Purpose - The aim of the research is to present the main challenges faced by Small and Medium Enterprises (SMEs) in the tourism industry, to build and enhance their value proposition within the framework of a digital environment. Design/methodology/approach - The authors carried out a review of the literature in databases using keywords. The selection of sources includes scientific articles and case studies based on different methods and contexts. Findings - The findings suggest that in a context characterized by the integration of the economy and the interference of Information and Communication Technologies (ICT), commercialization has become flexible and accessible. The above has had a tangible impact on the structure of the market and in the way in which the SMEs in the tourism industry are managed. Research limitations/implications - The study offers an up-to-date and global vision for future researchers through the review of the literature on SMEs located in the tourism industry in the context of a digital environment. Social implications - The study shows that to survive and grow, SMEs in the tourism sector must differentiate themselves from their competitors, evolve in their business model and rapidly integrate ICT in their organizational fabric. Originality/value - The construction of a value proposition for SMEs in the tourism sector should be settled on an understanding of the position held, on the competence of the competitors and the needs of the market

Aquacrop model calibration in potato and its use to estimate yield variability under field conditions

AquaCrop model estimates the crop pro ductivity decrease in response to water stress, determining the biomass (B) based on water productivity (WP) and accumulated transpiration (ΣTr); and the yield (Y) is calculated according to B and the harvest index (HI). AquaCrop was evaluated considering different WP values for 2010 late growing season to simulate crop yield of potato (Solanum tuberosum L.) cv. Spunta, in a commercial production field of 9 ha located in the green belt of Cordoba city (31 ̊30'S, 64 ̊08'W, 402 m asl), while monitoring in 2009 was used to verify the model. Canopy cover estimation by AquaCrop was adjusted using observed field data obtained from vertical digital photographs acquired at 2.5 m height. WP values of 15.8 and 31.6 (for C3 and C4 species, respectively) and two intermediate values 21 and 26.3 g·m−2 were considered to evaluate the model performance. While linear function between observed tuber yields and estimated by AquaCrop had always a correlation coefficient greater than 0.94 (p < 0.001), using WP = 26.3 and WP =31.6 g·m−2 presented overestimation, whereas with 15.8 g·m−2 had an opposite behavior, while WP = 21 g·m−2 was the value that produced the lowest estimation error. In addition, soil moisture from this estimated value of WP was highly correlated with measured water content in different areas of production field. The verification test shows that while the model slightly underestimates canopy cover, biomass was overestimated. After setting the coefficients of canopy cover development, the AquaCrop crop model estimated adequately potato yield for high production values that are less affected by lack of water, but in both years showed a tendency to overestimate the lowest yields, as was observed for other crops. Meanwhile, the dispersion between the observed and estimated yield was higher in the verification test because the sampling this year was more random.publishedVersionFil: de la Casa, Antonio Carlos. Universidad Nacional de Córdoba. Facultad de Ciencias Agropecuarias; Argentina.Fil: Ovando, Gustavo Gabriel. Universidad Nacional de Córdoba. Facultad de Ciencias Agropecuarias; Argentina.Fil: Bressanini, Luciano. Universidad Nacional de Córdoba. Facultad de Ciencias Agropecuarias; Argentina.Fil: Martínez, Jorge Mario. Universidad Nacional de Córdoba. Facultad de Ciencias Agropecuarias; Argentina

Kinetics of Drying Medicinal Plants by Hybridization of Solar Technologies

Historically, medicinal plants have always had an important place in medicine. Medicinal plants processing represents a great challenge, due to their compounds sensitive to the environmental conditions that surround and degrade them. Mostly of these plants require to be dry to preserve its safety and medicinal properties; therefore, for proper drying, it is necessary to use sustainable devices that protect the desirable characteristics of plants from direct radiation. In this work, the kinetics of dehydration of three medicinal plants are presented in an indirect solar dryer. In addition, the experimental results were adjusted to nine mostly used models, to estimate the drying conditions required to achieve a desired final moisture content. Modified Page and Page were the models with better fit to experimental results. Furthermore, a computational simulation of temperature evolution and distribution inside the dryer is presented. These results agree with those obtained experimentally

Un sistema experto de lógica difusa para evaluar la sustentabilidad de edificaciones

Se trata de una tesis en la que se presenta un sistema experto para evaluar cuantitativamente el manejo del agua, la energía y el confort de las edificaciones civiles.La presente tesis muestra como resultado final la elaboración de un sistema basado en Lógica Difusa (software) para evaluar la sustentabilidad en una edificación. Para la elaboración del mismo, en primera instancia se llevó a cabo un proceso de elección con algunas normas internacionales de certificación sustentable en edificaciones para determinar en cuál de ellas estaría basado el sistema programado. Una vez estudiadas las normas, se llega a la determinación de que la más apropiada es la norma LEED (Leadership In Energy and Enviromental Design) debido a su influencia a nivel mundial y no solo en cierta zona geográfica. Posteriormente a la elección, se toman tres de sus siete parámetros a evaluar debido a que son los de mayor peso y para efectos de la presente investigación, dichos parámetros a evaluar son: Manejo del Agua en Edificaciones, Manejo de la Energía en Edificaciones y Manejo del Confort dentro de las Edificaciones. Para cada una de ellas, en la investigación se presenta qué aspectos se evalúan, realizando una descripción acerca de lo que trata cada uno para un mayor entendimiento de los mismos y finalmente se muestra el desarrollo del software por medio del cual se obtiene un índice de sustentabilidad basado en Lógica Difusa. En capítulos finales se explica el proceso de toma de decisiones del sistema para que éste finalmente arroje un índice de sustentabilidad

Before and After the Reform: Fixed Line Internet Penetration in Mexican Households

Purpose – Despite being the second largest mobile market in Latin America regarding subscribers, Mexico’s penetration levels remain lower than the regional averages. The aim of this paper is to evaluate whether the Mexican 2013 Telecommunications and Broadcasting Reform helped mitigate or exacerbate the digital divide. In particular, we evaluate if the Reform had an impact on fixed-line internet penetration in Mexico. Methodology/approach/design – For the assessment, the 2010 Census and 2015 Intercensal Survey data used to create impact indexes through Generalized Linear Models (GLMs) estimations. Findings – Through a quintile analysis were confronted by results, with the intention of showing the average of internet penetration in each income group. The data obtained suggest that internet penetration had positive variations in all the quintiles indicating that recent regulatory changes in telecommunications matter had helped to reduce the digital divide. Practical implications – The poor and vulnerable groups remain at the digital exclusion; these groups need more digital inclusion actions

Estimación de la cobertura del suelo y evaluación de la fertilización nitrogenada en papa con registros de cámaras digitales convencionales y modificadas

Ponencia presentada en 42º Jornadas Argentinas de Informática (JAiiO). V Congreso Argentino de AgroInformática (CAI). Córdoba, Argentina, 16 al 20 de septiembre de 2013La fracción de suelo cubierta por un cultivo (CC) determina tanto la intercepción de radiación solar como el tamaño del aparato transpiratorio. El Nitrógeno en el cultivo de papa (Solanum tuberosum L.) afecta al rendimiento y la calidad de los tubérculos. Este trabajo propone desarrollar procedimientos di- gitales para estimar la cobertura de papa bajo distintas condiciones de fertilidad nitrogenada. Tanto la cámara convencional que produce imágenes a color como la modificada que genera imágenes de NDVI, como así también los procedi- mientos para estimar CC, se presentaron apropiados para detectar diferencias en CC asociadas a la condición de fertilidad existente. El método del cociente en- tre la banda verde y roja para determinar CC, pierde sensibilidad en la etapa de senescencia del cultivo La diferencia en la fertilización, produjo una disminu- ción anticipada de CC al final del ciclo lo que redujo tanto la productividad como la calidad comercial del cultivo.Fil: De la Casa, Antonio Carlos. Universidad Nacional de Córdoba. Facultad de Ciencias Agropecuarias; Argentina.Fil: Ovando, Gustavo Gabriel. Universidad Nacional de Córdoba. Facultad de Ciencias Agropecuarias; Argentina.Fil: Bressanini, Luciano. Universidad Nacional de Córdoba. Facultad de Ciencias Agropecuarias; Argentina.Fil: Martínez, Jorge Mario. Universidad Nacional de Córdoba. Facultad de Ciencias Agropecuarias; Argentina