Multi-core computation of transfer matrices for strip lattices in the Potts model

The transfer-matrix technique is a convenient way for studying strip lattices in the Potts model since the compu- tational costs depend just on the periodic part of the lattice and not on the whole. However, even when the cost is reduced, the transfer-matrix technique is still an NP-hard problem since the time T(|V|, |E|) needed to compute the matrix grows ex- ponentially as a function of the graph width. In this work, we present a parallel transfer-matrix implementation that scales performance under multi-core architectures. The construction of the matrix is based on several repetitions of the deletion- contraction technique, allowing parallelism suitable to multi-core machines. Our experimental results show that the multi-core implementation achieves speedups of 3.7X with p = 4 processors and 5.7X with p = 8. The efficiency of the implementation lies between 60% and 95%, achieving the best balance of speedup and efficiency at p = 4 processors for actual multi-core architectures. The algorithm also takes advantage of the lattice symmetry, making the transfer matrix computation to run up to 2X faster than its non-symmetric counterpart and use up to a quarter of the original space

Factibilidad técnica y análisis económico del mejoramiento térmico de viviendas a través de fachadas ventiladas en la ciudad de Curicó

126 p.El avance tecnológico y las nuevas exigencias en el estilo de vida de la sociedad contemporánea, llaman a la creación de sistemas tecnológicos que permitan, a través de elementos pasivos, mantener un estatus de comodidad y confort en las viviendas sin incurrir en un desmedro al medio ambiente. De acuerdo al estudio realizado en la presente memoria en las viviendas de Curicó, un 62% de las viviendas que se sometieron a estudio, no cumplen con los requerimientos mínimos de aislación, lo que conlleva a un uso deficiente de los materiales constructivos y usos de elementos de calefacción, que merman a largo y mediano plazo las condiciones, tanto ambientales como de salud en la ciudad. Se eligió intervenir los muros, pues son a través de estos elementos, en donde se producen las mayores deficiencias tanto constructivas como energéticas. Cerca del 40% de la humedad que ingresa a una vivienda proviene de los muros. En el presente trabajo se propone la construcción de un sistema de aislación térmica llamada fachada ventilada, como un sistema válido de aislación pasiva, la cual funciona por principio de convección en una cámara de aire en el exterior del muro, permitiendo un intercambio de calor entre las diferentes superficies y la regulación de la temperatura. Para ello se diseñó una fachada ventilada con una cámara de aire de 4 cm de espesor, utilizando las normas nacionales e internacionales, ocupando materiales que son accesibles para la región y usando parámetros de la localidad para que su funcionamiento sea eficiente, tanto en temporadas frías como cálidas. La fachada ventilada logra aumentar la gradiente de temperatura interior y exterior de 1,42°C a 3,21°C , mientras que para la humedad se logró disminuir en un 3,89% aumentando el confort térmico con estos parámetros en un 11,87% en relación a las mediciones realizadas, todas estas en temporada de meses fríos. Posteriormente se utilizó el software Ecotect analisys 2011 con el cual se verificó el funcionamiento de la fachada en temporadas más cálidas, encontrando una diferencia de temperatura con la colocación del sistema de 1,92 °C. En promedio. Con un coeficiente de variabilidad entre ambas mediciones del 72% demostrando así la tendencia de la fachada en mantener una distancia acorde a los requerimientos del ambiente en pro de un confort térmico al interior de la vivienda Palabras claves: Fachada ventilada, convección, eficiencia energética, espesor de cámara

Veamy: an extensible object-oriented C++ library for the virtual element method

This paper summarizes the development of Veamy, an object-oriented C++ library for the virtual element method (VEM) on general polygonal meshes, whose modular design is focused on its extensibility. The linear elastostatic and Poisson problems in two dimensions have been chosen as the starting stage for the development of this library. The theory of the VEM, upon which Veamy is built, is presented using a notation and a terminology that resemble the language of the finite element method (FEM) in engineering analysis. Several examples are provided to demonstrate the usage of Veamy, and in particular, one of them features the interaction between Veamy and the polygonal mesh generator PolyMesher. A computational performance comparison between VEM and FEM is also conducted. Veamy is free and open source software

A complete 12CO 2-1 map of M51 with HERA: I. Radial averages of CO, HI, and radio continuum

The mechanisms governing the star formation rate in spiral galaxies are not yet clear. The nearby, almost face-on, and interacting galaxy M51 offers an excellent opportunity to study at high spatial resolutions the local star formation laws. In this first paper, we investigate the correlation of H2, HI, and total gas surface densities with the star forming activity, derived from the radio continuum (RC), along radial averages out to radii of 12kpc. We have created a complete map of M51 in 12CO 2-1 at a resolution of 450kpc using HERA at the IRAM-30m telescope. These data are combined with maps of HI and the radio-continuum at 20cm wavelength. The latter is used to estimate the star formation rate (SFR), thus allowing to study the star formation efficiency and the local Schmidt law. The velocity dispersion from CO is used to study the critical surface density and the gravitational stability of the disk. The critical gas velocity dispersions needed to stabilize the gas against gravitational collapse in the differentially rotating disk of M51 using the Toomre criterion, vary with radius between 1.7 and 6.8 km/s. Observed radially averaged dispersions derived from the CO data vary between 28 km/s in the center and 8 km/s at radii of 7 to 9 kpc. They exceed the critical dispersions by factors Q_gas of 1 to 5. We speculate that the gravitational potential of stars leads to a critically stable disk

Climate and construction delays: case study in Chile

Purpose – Construction projects usually suffer delays, and the causes of these delays and its cost overruns have been widely discussed, the weather being one of the most recurrent. The purpose of this paper is to analyze the influence of climate on standard construction work activities through a case study. Design/methodology/approach – By studying the extent at which some weather variables impede outdoor work from being effectively executed, new maps and tables for planning for delays are presented. In addition, a real case regarding the construction of several bridges in southern Chile is analyzed. Findings – Few studies have thoroughly addressed the influences of major climatic agents on the most common outdoor construction activities. The method detailed here provides a first approximation for construction planners to assess to what extent construction productivity will be influenced by the climate. Research limitations/implications – Although this study was performed in Chile, the simplified method proposed is entirely transferable to any other country, however, other weather or combinations of weather variables could be needed in other environments or countries. Practical implications – The implications will help reducing the negative social, economic and environmental outcomes that usually emerge from project delays. Originality/value – Climatic data were processed using extremely simple calculations to create a series of quantitative maps and tables that would be useful for any construction planner to decide the best moment of the year to start a project and, if possible, where to build it