ETEA: A euclidean minimum spanning tree-Based evolutionary algorithm for multiobjective optimization

© the Massachusetts Institute of TechnologyAbstract The Euclidean minimum spanning tree (EMST), widely used in a variety of domains, is a minimum spanning tree of a set of points in the space, where the edge weight between each pair of points is their Euclidean distance. Since the generation of an EMST is entirely determined by the Euclidean distance between solutions (points), the properties of EMSTs have a close relation with the distribution and position information of solutions. This paper explores the properties of EMSTs and proposes an EMST-based Evolutionary Algorithm (ETEA) to solve multiobjective optimization problems (MOPs). Unlike most EMO algorithms that focus on the Pareto dominance relation, the proposed algorithm mainly considers distance-based measures to evaluate and compare individuals during the evolutionary search. Specifically in ETEA, four strategies are introduced: 1) An EMST-based crowding distance (ETCD) is presented to estimate the density of individuals in the population; 2) A distance comparison approach incorporating ETCD is used to assign the fitness value for individuals; 3) A fitness adjustment technique is designed to avoid the partial overcrowding in environmental selection; 4) Three diversity indicators-the minimum edge, degree, and ETCD-with regard to EMSTs are applied to determine the survival of individuals in archive truncation. From a series of extensive experiments on 32 test instances with different characteristics, ETEA is found to be competitive against five state-of-the-art algorithms and its predecessor in providing a good balance among convergence, uniformity, and spread.Engineering and Physical Sciences Research Council (EPSRC) of the United Kingdom under Grant EP/K001310/1, and the National Natural Science Foundation of China under Grant 61070088

Iodine content in running surface waters in areas with more intensive landscape management in the Czech Republic

The aim of this study has been to make an analysis and evaluation of iodine content in running surface waters in protected landscape areas (PLA) in the Czech Republic. Water samples were taken in 2009-2011 in Jeseníky PLA (Rapotín locality) and in Šumava PLA (Arnoštov and Lipno localities), and in 2009-2010 in the upper course of the Blanice River and its tributaries in and outside of Šumava PLA. Iodine was determined by the ICP-MS method. The average iodine content was 1.55±0.33 μg dm-3 (n = 41) in Jeseníky PLA and 2.58±0.33 μg dm-3 (n = 24) and 2.29±0.84 μg dm-3 (n = 30) in Šumava PLA. The average iodine content in water samples of the Blanice River and its tributaries localized in Šumava PLA was 2.27±0.65 and 2.38±0.66 μg dm-3 and outside of Šumava PLA it equalled 2.90±0.68 and 3.26±1.51 μg dm-3. The lowest concentration of 1.43 μg dm-3 was found out in a sample from the Spálenecký brook (Šumava PLA), and the highest one, 7.63 μg dm-3, was determined in a sample from the Živný brook, which flows below the town Prachatice. Higher concentrations were measured in the summer season: 3.05±0.35 (Blanice) and 3.63±1.24 μg dm-3 (tributaries), while lower ones were determined in the spring season: 1.48±0.30 (Blanice) and 2.37±1.12 μg dm-3 (tributaries). The results confirm the low iodine content in the environment of Jeseníky and Šumava Mts., and the self-purification capacity of the Blanice River even when it is stressed with anthropogenic iodine