A Study of the Combination of Variation Operators in the NSGA-II Algorithm

Multi-objective evolutionary algorithms rely on the use of variation operators as their basic mechanism to carry out the evolutionary process. These operators are usually fixed and applied in the same way during algorithm execution, e.g., the mutation probability in genetic algorithms. This paper analyses whether a more dynamic approach combining different operators with variable application rate along the search process allows to improve the static classical behavior. This way, we explore the combined use of three different operators (simulated binary crossover, differential evolution’s operator, and polynomial mutation) in the NSGA-II algorithm. We have considered two strategies for selecting the operators: random and adaptive. The resulting variants have been tested on a set of 19 complex problems, and our results indicate that both schemes significantly improve the performance of the original NSGA-II algorithm, achieving the random and adaptive variants the best overall results in the bi- and three-objective considered problems, respectively.UNIVERSIDAD DE MÁLAGA. CAMPUS DE EXCELENCIA INTERNACIONAL ANDALUCÍA TEC

Two-neutrino double electron capture on 124^{124}Xe based on an effective theory and the nuclear shell model

We study the two-neutrino double electron capture on $^{124}$Xe based on an effective theory (ET) and large-scale shell model calculations, two modern nuclear structure approaches that have been tested against Gamow-Teller and double-beta decay data. In the ET, the low-energy constants are fit to electron capture and $\beta^{-}$ transitions around xenon. For the nuclear shell model, we use an interaction in a large configuration space that reproduces the spectroscopy of nuclei in this mass region. For the dominant transition to the $^{124}$Te ground state, we find half-lives $T^{2\nu{\rm ECEC}}_{1/2}=(1.3-18)\times 10^{22}$ y for the ET and $T^{2\nu{\rm ECEC}}_{1/2} = (0.43-2.9)\times 10^{22}$ y for the shell model. The ET uncertainty leads to a half-life almost entirely consistent with present experimental limits and largely within the reach of ongoing experiments. The shell model half-life range overlaps with the ET, but extends less beyond current limits. Our findings thus suggest that the two-neutrino double electron capture on $^{124}$Xe has a good chance to be discovered by ongoing or future experiments. In addition, we present results for the two-neutrino double electron capture to excited states of $^{124}$Te.Comment: 5 pages, 2 figure

Approximate solutions in space mission design

In this paper, we address multi-objective space mission design problems. From a practical point of view, it is often the case that,during the preliminary phase of the design of a space mission, the solutions that are actually considered are not 'optimal' (in the Pareto sense)but belong to the basin of attraction of optimal ones (i.e. they are nearly optimal). This choice is motivated either by additional requirements that the decision maker has to take into account or, more often, by robustness considerations. For this, we suggest a novel MOEA which is a modification of the well-known NSGA-II algorithm equipped with a recently proposed archiving strategy which aims at storing the set of approximate solutions of a given MOP. Using this algorithm we will examine some space trajectory design problems and demonstrate the benefit of the novel approach

Designing a Solid Waste Infrastructure Management Model for Integration into a National Infrastructure System-of Systems

Solid waste management is arguably one of the most important municipal services provided by government1. Given the rapid socio-economic changes that are projected to take place in the UK2 it is important that we plan our future waste management capacity to ensure the continuance of this valuable service. The Solid Waste Infrastructure Management System (SWIMS) model was designed to model the current solid waste infrastructure requirements (from collection through treatment and disposal) for an area based on its solid waste arisings. SWIMS allows an area’s waste treatment capacity requirements to be forecast against future socio-economic change to help decision-makers choose the right solid waste infrastructure given their goals, constraints and ideas about future conditions. The modelling of solid waste management systems has been carried out since the 1970s3 and such modelling exercises have been undertaken for numerous different geographical areas around the world4. However, the SWIMS model is unique in that it was designed to also operate within a larger national infrastructure system-of-systems model, including interdependencies with other infrastructure sectors including energy, water and waste water. To achieve such flexibility the SWIMS model was carefully designed using object-oriented programming (OOP) principles. In documenting this model’s design methodology we hope to demonstrate how applying OOP principles enables such models to not only be more flexible and more easily integrated with other modelling efforts, but also more easily understood by system experts and end-users

VSD-MOEA: A Dominance-Based Multiobjective Evolutionary Algorithm with Explicit Variable Space Diversity Management

Most state-of-the-art Multiobjective Evolutionary Algorithms (moeas) promote the preservation of diversity of objective function space but neglect the diversity of decision variable space. The aim of this article is to show that explicitly managing the amount of diversity maintained in the decision variable space is useful to increase the quality of moeas when taking into account metrics of the objective space. Our novel Variable Space Diversity-based MOEA (vsd-moea) explicitly considers the diversity of both decision variable and objective function space. This information is used with the aim of properly adapting the balance between exploration and intensification during the optimization process. Particularly, at the initial stages, decisions made by the approach are more biased by the information on the diversity of the variable space, whereas it gradually grants more importance to the diversity of objective function space as the evolution progresses. The latter is achieved through a novel density estimator. The new method is compared with state-of-art moeas using several benchmarks with two and three objectives. This novel proposal yields much better results than state-of-the-art schemes when considering metrics applied on objective function space, exhibiting a more stable and robust behavior

Piecewise Linear Representation Segmentation as a Multiobjective Optimization Problem

Proceedings of: Forth International Workshop on User-Centric Technologies and applications (CONTEXTS 2010). Valencia, September 7-10, 2010Actual time series exhibit huge amounts of data which require an unaffordable computational load to be processed, leading to approximate representations to aid these processes. Segmentation processes deal with this issue dividing time series into a certain number of segments and approximating those segments with a basic function. Among the most extended segmentation approaches, piecewise linear representation is highlighted due to its simplicity. This work presents an approach based on the formalization of the segmentation process as a multiobjetive optimization problem and the resolution of that problem with an evolutionary algorithm.This work was supported in part by Projects CICYT TIN2008-06742-C02-02/TSI, CICYT TEC2008-06732-C02-02/TEC, CAM CONTEXTS (S2009/TIC-1485) and DPS2008-07029-C02-02.Publicad

Dynamic Multi-Objective Optimization With jMetal and Spark: a Case Study

Technologies for Big Data and Data Science are receiving increasing research interest nowadays. This paper introduces the prototyping architecture of a tool aimed to solve Big Data Optimization problems. Our tool combines the jMetal framework for multi-objective optimization with Apache Spark, a technology that is gaining momentum. In particular, we make use of the streaming facilities of Spark to feed an optimization problem with data from different sources. We demonstrate the use of our tool by solving a dynamic bi-objective instance of the Traveling Salesman Problem (TSP) based on near real-time traffic data from New York City, which is updated several times per minute. Our experiment shows that both jMetal and Spark can be integrated providing a software platform to deal with dynamic multi-optimization problems.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Solving a Real-World Structural Optimization Problem With a Distributed SMS-EMOA Algorithm

This paper addresses a real-world optimization problem in civil engineering. It lies in the dimensioning of a 162m long bridge composed of 1584 bars so that both its weight and its deformation are to be minimized. Evaluating each possible configuration of the bridge takes several seconds and, as a consequence, running a metaheuristic for several thousands of evaluations would require many days on one single processor. Our approach has been to develop a distributed master/worker version of SMS-EMOA, an indicator-based multiobjective algorithm. By combining the Java implementation of the algorithm in jMetal with the Condor distributed scheduler, we have been able to use more than 350 cores to obtain accurate results in a reasonable amount of time.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

A Descent Method for Equality and Inequality Constrained Multiobjective Optimization Problems

In this article we propose a descent method for equality and inequality constrained multiobjective optimization problems (MOPs) which generalizes the steepest descent method for unconstrained MOPs by Fliege and Svaiter to constrained problems by using two active set strategies. Under some regularity assumptions on the problem, we show that accumulation points of our descent method satisfy a necessary condition for local Pareto optimality. Finally, we show the typical behavior of our method in a numerical example

Evolución del contenido de macro conidios de Fusarium en el aire de la ciudad de Ourense (NW España).

MÉNDEZ, J., SEIJO, M. C. & IGLESIAS, I. 2001. Evolución del contenido de macroconidios de Fusarium en el aire de la ciudad de Ourense (NW España). Bot. Complutensis 25: 73-82. En este trabajo se presentan los resultados obtenidos para el tipo conidial Fusarium, en la atmósfera de la ciudad de Ourense tras el muestreo aerobiológico realizado durante los años 1993-1996 utilizando para ello un captador volumétrico tipo Hirst, modelo Lanzoni VPPS 2000. Se analiza tanto el comportamiento estacional como intradiario así como su relación con los diferentes parámetros meteorológicos. Las mayores concentraciones se han registrado durante los meses de mayo y junio, exceptuando el año 1996 que tienen lugar en el mes de septiembre y entre la 01:00 y las 07:00 de la mañana, habiéndose observado diferencias cuantitativas importantes entre el año 1993 y el resto de los años de estudio. Las correlaciones obtenidas entre las concentraciones medias diarias y los diferentes parámetros meteorológicos demuestran que, para este tipo conidial tanto la precipitación como la humedad relativa, resultan siempre significativa y positivamente correlacionadas mientras que la temperatura máxima, media, mínima y las horas de sol varían según los años tanto en el signo como en el grado de significación de las correlaciones obtenidas.MÉNDEZ, J., SEIJO, M. C. & IGLESIAS, I. 2001. Evolution of the content of macroconidia of Fusarium in the air of Ourense (NW Spain) Bot. Complutensis 25: 73-82. In this work, we present the results obtained for the spore-type Fusarium in the atmosphere of the city Ourense during 199-1996, period in which a volumetric spore-trap VPPS 2000 was used. Beside seasonal and intradiurnal variations, the relationships between meteorological parameters and spore concentrations have been also analysed. The maximun values for airborne spores were always registered during May and June only in the year 1996 the maximum values are registered during September, especially between 01:00 and 07:00 (Spanish official time). On spite of the fact that important quantitative differences were observed between 1993 and the rest of the years, the correlations obtained between 73 José Méndez et al. Evolución del contenido de macroconidios de Fusarium... daily mean spore concentrations and the different meteorological parameters showed that rainfall and relative humidity were always positively correlated, whereas the correlations with maximun, minimum and mean temperature and sunshine hours were variable during the different years in sing and signification level