Combining model-based and genetics-based offspring generation for multi-objective optimization using a convergence criterion

Abstract — In our previous work [1], it has been shown that the performance of evolutionary multi-objective algorithms can be greatly enhanced if the regularity in the distribution of Pareto-optimal solutions is taken advantage using a probabilistic model. This paper suggests a new hybrid multi-objective evolutionary algorithm by introducing a convergence based criterion to determine when the model-based method and when the genetics-based method should be used to generate offspring in each generation. The basic idea is that the genetics-based method, i.e., crossover and mutation, should be used when the population is far away from the Pareto front and no obvious regularity in population distribution can be observed. When the population moves towards the Pareto front, the distribution of the individuals will show increasing regularity and in this case, the model-based method should be used to generate offspring. The proposed hybrid method is verified on widely used test problems and our simulation results show that the method is effective in achieving Pareto-optimal solutions compared to two state-of-the-art evolutionary multi-objective algorithms: NSGA-II and SPEA2, and our pervious method in [1]. I

Mouse sperm membrane potential: changes induced by Ca2+

AbstractMouse sperm resting membrane potential (Er) (−42±8.8 mV), determined with a potential sensitive dye, depended on extracellular K+ and, in the absence of extracellular Ca2+ ([Ca2+]e), on external Na+ ([Na+]e). Ca2+ addition (>5 μM) to sperm in Ca-free media induced a transient hyperpolarization (Ca-ith) which strongly depended on [Na+]e and less on external Cl− ([Cl−]e). Cd2+ and Mn2+ (μM) mimicked the Ca2+ effect, but not Ba2+. The Ca-ith was partially inhibited by ouabain (74%, IC50 = 5.8 μM) and niflumic acid (38%, IC50 = 240 μM), indicating the participation of the Na-K ATPase and Cl− channels. In Ca-free low-Na+ media, Ca2+ addition caused a depolarization sensitive to: nimodipine (25 μM), trifluoperazine (12.5 μM) and Mg2+ (1.2 mM), suggesting the participation of Ca2+ channels. Since some inhibitors of the sperm Ca-ith block the acrosome reaction (AR), both processes may share transport systems

Plan Acquisition Through Intentional Learning in BDI Multi-Agent Systems

Multi-Agent Systems (MAS), a technique emanating from Distributed Artificial Intelligence, is a suitable technique to study complex systems. They make it possible to represent and simulate both elements and interrelations of systems in a variety of domains. The most commonly used approach to develop the individual components (agents) within MAS is reactive agency. However, other architectures, like cognitive agents, enable richer behaviours and interactions to be captured and modelled. The well-known Belief-Desire-Intentions architecture (BDI) is a robust approach to develop cognitive agents and it can emulate aspects of autonomous behaviour and is thus a promising tool to simulate social systems. Machine Learning has been applied to improve the behaviour of agents both individually or collectively. However, the original BDI model of agency, is lacking learning as part of its core functionalities. To cope with learning, the BDI agency has been extended by Intentional Learning (IL) operating at three levels: belief adjustment, plan selection, and plan acquisition. The latter makes it possible to increase the agent’s catalogue of skills by generating new procedural knowledge to be used onwards. The main contributions of this thesis are: a) the development of IL in a fully-fledged BDI framework at the plan acquisition level, b) extending IL from the single-agent case to the collective perspective; and c) a novel framework that melts reactive and BDI agents through integrating both MAS and Agent-Based Modelling approaches, it allows the configuration of diverse domains and environments. Learning is demonstrated in a test-bed environment to acquire a set of plans that drive the agent to exhibit behaviours such as target-searching and left-handed wall-following. Learning in both decision strata, single and collective, is tested in a more challenging and socially relevant environment: the Disaster-Rescue problem

Politics of oil in Venezuela: A decision-making analysis of PDVSA's internationalisation policy.

The high degree of international vertical integration achieved by the Venezuelan state oil enterprise, Petroleos de Venezuela S.A. (PDVSA), has placed it among the most important oil multinationals (MNs). The policy of creating downstream outlets through the establishment of foreign direct investments (FDIs) in the form of refinery assets was given the term of 'internationalisation'. By analysing PDVSA's internationalisation policy, the thesis explores the difficulties encountered by a major state-owned enterprise (SOE) from a developing country in its efforts to grow beyond national borders. The study focuses on the impact of democratic bargaining on the process of oil policymaking in Venezuela, stressing the constraints posed by politics on PDVSA's efforts to expand its foreign operations. Specifically, the study examines the intricate policymaking process that shaped the origins and the development of PDVSA's internationalisation policy, underlying the events and factors that influenced each one of its three distinguishable phases: adoption, formulation, and implementation. The tensions between politics and corporate strategy are highlighted at the core of the policymaking process. The study also looks at the relationship between the oil industry and the other two key decision-making centres involved in the oil policymaking process: the executive and Congress. In exploring the ways in which each one of them sought to influence policy outcome, the study attempts to gain insight into the main factors that prompted the tensions among the policy actors involved. Three environments, or pressure-generating centres, constantly exert influence on the oil industry: the oil market, the political context and the government's financial situation. By seeking to determine the industry's response to their pervasive influence on policy formulation and implementation, this research ascertains the extent to which these variables influenced the decision-making process that characterised PDVSA's internationalisation policy. Being too powerful a company in a developing country context where the executive and the legislature find it increasingly difficult to exert their means of control over it had the effect of minimising some of PDVSA's characteristics as SOE: accountability to Congress and subordination to the executive. The thesis argues that as a result of its role as oil MN PDVSA has minimised some of its attributes as SOE. In turn, the more PDVSA has diminished its status as SOE, the more the government has increased its dependence over it. The successful accomplishment of PDVSA's internationalisation policy has stressed this equation, highlighting the contentious interaction between an excessively dependent govemment and a company struggling to reconcile its roles as both a SOE and a MN. By examining the policy process that brought about the international expansion of a large SOE from a developing country, the findings of the thesis contribute significantly to the political science and public administration literatures and suggests new paths for further research in the area of public policymaking processes. (Abstract shortened by UMI.)

Gender priming in Italian

The goals of the present study were: (1) to determine whether grammatical gender on a noun modifier can prime recognition of the following noun; (2) to determine whether the priming effect involves facilitation, inhibition or both, and (3) to compare performance across three different tasks that vary in the degree to which explicit attention to gender is required, including word repetition, gender monitoring and grammaticality judgment. Results showed a clear effect of gender priming, involving both facilitation and inhibition. Priming was observed whether or not the subjects ’ attention was directed to gender per se. Results suggest that gender priming involves a combination of controlled, post-lexical processing and automatic, pre-lexical processing. Implications for different models of lexical access are discussed, with special reference to modular vs. interactive-activation theories. Why grammatical priming? The issue of whether gender can be a useful prime in lexical access is a particular example of a more general problem: How can context influence the nature and timing of information access during lexical processing? The answer to this question has consequences for theories of language comprehension, including the contrast between modularity and interactive models of lexical access (for reviews, see Balota, 1992; Frauenfelder & Tyler (Eds.), 1987; Levelt (Ed.), 1992). If grammatical gender does contribute to word recognition, then it can be said to constitute an example of grammatical priming. Two earlier studies provided evidence for faster lexical decisions when the prime and target are preceded by a syntactically appropriate context (Goodman, McClelland & Gibbs, 1981, in a study of English), or when they were preceded by an appropriat