Evolutionary computation of forests with Degree- and Role-Constrained Minimum Spanning Trees

Finding the degree-constrained minimum spanning tree (DCMST) of a graph is a widely studied NP-hard problem. One of its most important applications is network design. Here we deal with a new variant of the DCMST problem, which consists of finding not only the degree- but also the role-constrained minimum spanning tree (DRCMST), i.e., we add constraints to restrict the role of the nodes in the tree to root, intermediate or leaf node. Furthermore, we do not limit the number of root nodes to one, thereby, generally, building a forest of DRCMSTs. The modeling of network design problems can benefit from the possibility of generating more than one tree and determining the role of the nodes in the network. We propose a novel permutation-based representation to encode these forests. In this new representation, one permutation simultaneously encodes all the trees to be built. We simulate a wide variety of DRCMST problems which we optimize using eight different evolutionary computation algorithms encoding individuals of the population using the proposed representation. The algorithms we use are: estimation of distribution algorithm, generational genetic algorithm, steady-state genetic algorithm, covariance matrix adaptation evolution strategy, differential evolution, elitist evolution strategy, non-elitist evolution strategy and particle swarm optimization. The best results are for the estimation of distribution algorithms and both types of genetic algorithms, although the genetic algorithms are significantly faster.

Conflicts for control of Mapuche-Pehuenche land and natural resources in the Biobío highlands

Análisis de las políticas aplicadas por el Estado chileno y sus efectos en el uso del territorio por parte de las comunidades indígenas de la zona del Alto Bíobio. Se observa que históricamente las comunidades han ido perdiendo el control de sus tierras

Urbanization patterns and their impacts on social restructuring of urban space in Chilean mid-cities: The case of Los Angeles, Central Chile

El artículo analiza las relaciones entre los cambios de uso en el territorio rural de la región del Biobío y sus efectos en el crecimiento urbano y demográfico de una ciudad de tamaño medio. En forma específica se estudia el desarrollo de la industria forestal y sus efectos sobre el proceso urbano de Los Angeles.

Determination of spectral variations by means of component cells useful for CPV rating and design

A methodology is presented to determine both the short-term and the long-term influence of the spectral variations on the performance of Multi-Junction (MJ) solar cells and Concentrating "This is the peer reviewed version of the following article: R. Núñez, C. Domínguez, S. Askins, M. Victoria, R. Herrero, I. Antón, and G. Sala, “Determination of spectral variations by means of component cells useful for CPV rating and design,” Prog. Photovolt: Res. Appl., 2015., which has been published in final form at http://onlinelibrary.wiley.com/doi/10.1002/pip.2715/full. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving [http://olabout.wiley.com/WileyCDA/Section/id-820227.html#terms]." Photovoltaic (CPV) modules. Component cells with the same optical behavior as MJ solar cells are used to characterize the spectrum. A set of parameters, namely Spectral Matching Ratios (SMRs), is used to characterize spectrally a particular Direct Normal Irradiance (DNI) by comparison to the reference spectrum (AM1.5D-ASTM-G173-03). Furthermore, the spectrally corrected DNI for a given MJ solar cell technology is defined providing a way to estimate the losses associated to the spectral variations. The last section analyzes how the spectrum evolves throughout a year in a given place and the set of SMRs representative for that location are calculated. This information can be used to maximize the energy harvested by the MJ solar cell throughout the year. As an example, three years of data recorded in Madrid shows that losses lower than 5% are expected due to current mismatch for state-of-the-art MJ solar cells.

Spectral study and classification of worldwide locations considering several multijunction solar cell technologies

Multi-junction solar cells are widely used in high-concentration photovoltaic systems (HCPV) attaining the highest efficiencies in photovoltaic energy generation. This technology is more dependent on the spectral variations of the impinging Direct Normal Irradiance (DNI) than conventional photovoltaics based on silicon solar cells and consequently demands a deeper knowledge of the solar resource characteristics. This article explores the capabilities of spectral indexes, namely, spectral matching ratios (SMR), to spectrally characterize the annual irradiation reaching a particular location on the Earth and to provide the necessary information for the spectral optimization of a MJ solar cell in that location as a starting point for CPV module spectral tuning. Additionally, the relationship between such indexes and the atmosphere parameters, such as the aerosol optical depth (AOD), precipitable water (PW), and air mass (AM), is discussed using radiative transfer models such as SMARTS to generate the spectrally-resolved DNI. The network of ground-based sun and sky-scanning radiometers AERONET (AErosol RObotic NETwork) is exploited to obtain the atmosphere parameters for a selected bunch of 34 sites worldwide. Finally, the SMR indexes are obtained for every location, and a comparative analysis is carried out for four architectures of triple junction solar cells, covering both lattice match and metamorphic technologies. The differences found among cell technologies are much less significant than among locations.

Leslie Martin, Colin St. John Wilson y James Stirling : revisión de la modernidad en la arquitectura británica = Leslie Martin, Colin St. John Wilson and James Stirling : review of modernity in British architecture

La búsqueda de nuevas formas de modernidad se convirtió en la cuestión principal de la obras desarrolladas por Leslie Martin, Colin St. John Wilson y James Stirling entre los años 1955 y 1970. Enmarcadas dentro de la sensibilidad surgida en la posguerra británica, su profundo sentido crítico supone una renovada interpretación de alguno fundamentos del Movimiento Moderno así como la reflexión sobre la modificación y el uso de formas que tienen sus raíces en la tradición cultural. Esta investigación se estructura en cuatro temas ampliamente debatidos y que han articulado parte de la revisión moderna a lo largo de la segunda mitad del siglo XX: » la abstracción y el realismo » la revisión de la idea funcionalista » la reconsideración de los arquetipos formales » la relación entre forma y contexto urbano se muestran como base crítica para las obras seleccionadas. La tendencia hacia el realismo surgió como respuesta a la voluntad de universalidad (y objetividad) que representó el lenguaje abstracto, del mismo modo que la revisión de la idea funcionalista pretendió superar la consideración de la obra arquitectónica como producto racional de su función y tecnología. La reconsideración de los arquetipos de la tradición, a su vez, muestra una preocupación por el significado de las formas culturales del pasado, una cuestión igualmente decisiva en la renovada atención a la estructura de la ciudad histórica. Estos temas evidencian un interés por ampliar la arquitectura moderna sin que el reconocimiento de las formas del pasado suponga un distanciamiento respecto al futuro. La idea de revisión, asimismo, se convierte en estrategia a la hora de encontrar nuevas respuestas. Si algunos de los principios del Movimiento Moderno surgen como reacción al clasicismo Beaux Arts que le precedió, las propuestas analizadas muestran la validez operativa de este enfoque para crear obras de una intensa modernidad. Su interés, por lo tanto, no solo radica en su consideración como objetos de estudio que amplían nuestro conocimiento de un período determinado, sino como tradición reciente que sirve de base crítica para la práctica actual. ABSTRACT The search of new forms of modernity became the main theme of the works developed by Leslie Martin, Colin St. John Wilson and James Stirling between 1955 and 1970. Belonging to the sensitivity emerged in postwar Britain, their deep critical sense encourages a renewed interpretation of some principles of Modern Movement and a reflection about the modification or the use of forms that are rooted in cultural tradition. This research is divided into four themes widely discussed and which has articulated part of modern review along the second half of the twentieth century: » Abstraction and realism » Review of Functionalism » The reconsideration of the formal archetypes » The relationship between form and urban context are shown as critical base for the selected works. The trend toward realism arose in response to the will of universality (and objectivity) that represented the abstract language, just as the review of Functionalism aimed to overcome the consideration of architecture's work as rational product of its function and technology. The reconsideration of traditional archetypes, in turn, shows a concern for the meaning of the cultural forms, a matter equally decisive in the renewed attention to the structure of the historical city. These themes evidence an interest to extend modern architecture, without thereby the recognition of the past forms imply a distancing regarding the future. The idea of review also becomes strategy in finding new answers. If some principles of the Modern Movement arose in reaction to Beaux-Arts classicism which preceded it, the analyzed proposals show the operational validity of this approach to create works of a strong modernity. Their interest, therefore, lies not only in its consideration as study cases that broaden our knowledge of a certain period, but as a recent tradition which serves as a critic basis for the current practice.