In this paper we develop a study on several types of parallel genetic algorithms (PGAs). Our motivation is to bring some uniformity to the proposal, comparison, and knowledge exchange among the traditionally opposite kinds of serial and parallel GAs. We comparatively analyze the properties of steady-state, generational, and cellular genetic algorithms. Afterwards, this study is extended to consider a distributed model consisting in a ring of GA islands. The analyzed features are the time complexity, selection pressure, schema processing rates, efficacy in finding an optimum, efficiency, speedup, and resistance to scalability. Besides that, we briefly discuss how the migration policy affects the search. Also, some of the search properties of cellular GAs are investigated. The selected benchmark is a representative subset of problems containing real world difficulties. We often conclude that parallel GAs are numerically better and faster than equivalent sequential GAs. Our aim is to shed some light on the advantages and drawbacks of various sequential and parallel GAs to help researchers using them in the very diverse application fields of the evolutionary computation. 相似文献
Recently, we developed a GIS-Integrated Integral Risk Index (IRI) to assess human health risks in areas with presence of environmental pollutants. Contaminants were previously ranked by applying a self-organizing map (SOM) to their characteristics of persistence, bioaccumulation, and toxicity in order to obtain the Hazard Index (HI). In the present study, the original IRI was substantially improved by allowing the entrance of probabilistic data. A neuroprobabilistic HI was developed by combining SOM and Monte Carlo analysis. In general terms, the deterministic and probabilistic HIs followed a similar pattern: polychlorinated biphenyls (PCBs) and light polycyclic aromatic hydrocarbons (PAHs) were the pollutants showing the highest and lowest values of HI, respectively. However, the bioaccumulation value of heavy metals notably increased after considering a probability density function to explain the bioaccumulation factor. To check its applicability, a case study was investigated. The probabilistic integral risk was calculated in the chemical/petrochemical industrial area of Tarragona (Catalonia, Spain), where an environmental program has been carried out since 2002. The risk change between 2002 and 2005 was evaluated on the basis of probabilistic data of the levels of various pollutants in soils. The results indicated that the risk of the chemicals under study did not follow a homogeneous tendency. However, the current levels of pollution do not mean a relevant source of health risks for the local population. Moreover, the neuroprobabilistic HI seems to be an adequate tool to be taken into account in risk assessment processes. 相似文献
A cooperative game with transferable utilities– or simply a TU-game – describes a situation in which players can obtain certain payoffs by cooperation. A solution concept for these games is a function which assigns to every such a game a distribution of payoffs over the players in the game.
Famous solution concepts for TU-games are the Shapley value and the Banzhaf value. Both solution concepts have been axiomatized in various ways.
An important difference between these two solution concepts is the fact that the Shapley value always distributes the payoff
that can be obtained by the `grand coalition' consisting of all players cooperating together while the Banzhaf value does
not satisfy this property, i.e., the Banzhaf value is not efficient. In this paper we consider the normalized Banzhaf value which distributes the payoff that can be obtained by the `grand coalition' proportional to the Banzhaf values of the players.
This value does not satisfy certain axioms underlying the Banzhaf value. In this paper we introduce some new axioms that characterize
the normalized Banzhaf value. We also provide an axiomatization of the Shapley value using similar axioms.
Received: 10 April 1996 / Accepted: 2 June 1997 相似文献
We propose an influence diagnostic methodology for linear regression models with stochastic restrictions and errors following elliptically contoured distributions. We study how a perturbation may impact on the mixed estimation procedure of parameters in the model. Normal curvatures and slopes for assessing influence under usual schemes are derived, including perturbations of case-weight, response variable, and explanatory variable. Simulations are conducted to evaluate the performance of the proposed methodology. An example with real-world economy data is presented as an illustration. 相似文献
The establishment of the European Higher Education Area has involved specifying lists of professional competencies that programs are expected to develop, and with this the need for procedures to measure how every course within a higher education program is aligned with the program's competencies. We propose an instrument for characterizing this alignment, a process that we call assessing the relevance of a course. Using information from the course syllabus (objectives, contents and assessment scheme), our instrument produces indicators for characterizing the syllabus in terms of a competence list and for assessing its coherence. Because assessment involves quality, the results obtained can also be used to revise and improve the course syllabus. We illustrate this process with an example of a methods course from a mathematics teacher education program at a Spanish university. 相似文献
Urban Ecosystems - Urban streams provide important ecosystem services to cities’ population, from the maintenance of urban biodiversity, temperature, humidity and air quality to improving... 相似文献
We analyze cooperation of individuals in a family context, using a Public Good game. In a lab experiment, 165 individuals from 55 three-generation families (youth, parent, and grandparent) play a repeated Public Good game in three different treatments: one in which three members of the same family play each other (family), a second with the youth and two non-family members, while preserving the previous generational structure (inter-generational), and a third in which three randomly-selected players play each other (random). We find that all the age groups cooperate more when playing with relatives, indicating that family ties may have a positive relationship to contributions to the Public Good. We also find that this trend is more evident for the youths and the parents than for the grandparents. Furthermore, young individuals tend to cooperate less than older generations, especially in non-family treatments. Our results serve as evidence of the relationship between family ties and inter-generational cooperative behaviors.
This article describes the design process and main features of an instrument developed for use in the specialist area of intervention in care homes for older persons. The essential aim of ISD-1 (instrument for social diagnosis) is to permit the correct formulation of social diagnoses and to standardise and define the professional language used by social workers. Its content has been organised into 4 dimensions of social diagnosis, divided into 15 sub-dimensions containing 83 diagnostic categories. This work was performed in Spain, in the 24 care homes of the Madrid Social Care Agency of the Community of Madrid, involving the participation of the 40 social workers practising in these centres. ISD-1 is an easily understood and used tool, of potential use for social workers practising in care homes for older persons and capable of being adapted for use in other institutional environments, as well as being capable of adaptation and translation for its application in other countries. 相似文献
This article studies the voters of DENK, the first immigrant party to gain seats in a national parliament. It builds further on the existing literature on how immigrants and people from immigrant descent vote in Western European countries. From the literature we derive seven expectations about the kind of voters that are likely to vote for an immigrant party in terms of their political cynicism, attitudes towards economic, globalisation and moral issues. We find that DENK voters are younger Muslims, who have conservative views on moral matters, cynical attitudes towards politics, right-wing views on economic matters and progressive views on issues that pertain to the globalisation dimension, such as immigration, integration and Islam and in particular discrimination. This article uses VAA data to construct a matched sample that in terms of key variables is representative for voters with and without a migration background. 相似文献