Scientia

Particle Swarm Optimization with inertia non-monotonic control

Tiago Silveira — 2009-12-30

This work presents a mechanism to reduce the chances of the optimization process of nonlinear functions stagnating in local minima, using the meta-heuristic “Particle Swarm Optimization”. This mechanism is a nonmonotonic way to control the particle inertia, which is one of the factors responsible for movement during the optimization process. The experimental results were compared to the original PSO model aiming to show the potential to find a better solution related to the benchmark functions for complex problems. Finally, a comparison of both models was made in the adjustment of synaptic weights of a Multi-Layer Perceptron neural network obtaining interesting results.

Keywords: swarm intelligence, Particle Swarm Optimization, artificial life, artificial neural network MLP.

Control of the population diversity in genetic algorithms applied to the protein structure prediction problem

Vinicius Tragante do Ó — 2009-12-30

Genetic Algorithms (GAs), a successful approach for optimization problems, usually fail when employed in the standard configuration in the protein structure prediction problem, since the solution space is very large and the population converges before a reasonable percentage of the possible solutions is explored. Thus, this work investigates the effect of increasing the diversity of the population on this problem by using Hypermutation and Random Immigrants, two traditional population diversity control schemes, in the structure prediction of the proteins Crambin (PDB 1CRN), Met-Enkephalin (PDB 1PLW), and DNA-Ligand (PDB 1ENH). Results show a significant reduction of the minimal energy found, thanks to the diversity, but this does not necessarily means a higher similarity to the original structure.

Keywords: evolutionary computing, genetic algorithms, hypermutation, random immigrants, protein structure prediction.

Particle Swarm Optimization applied to robotic squad coordination

Gustavo Pessin — 2009-12-30

In this paper it is described the modeling, implementation and evaluation of the Particle Swarm Optimization (PSO) efficiency when applied to robotic group formation and coordination. The robotic task is performed over a natural disaster, simulated as a forest fire. The robot squad mission is to surround the fire and avoid fire’s propagation. Experiments have been made with several parameter’s variation seeking to get the more efficient swarm performance. This paper describes all performed experiments detailing all sets of parameters, including positive and negative results. The simulation’s results showed that with an adequate set of parameters is possible to get satisfactory strategic positions for a multi-robotic system’s operation.

Keywords: Particle Swarm Optimization, coordination, multi-robotics systems.

Continuum software infrastructure for ubiquitous computing: A service-based approach

Cristiano Costa — 2009-12-30

The latest technological advances, which introduced innovative and more affordable devices, have contributed to boost the practical application of research in the field of ubiquitous computing (ubicomp). For the development of applications in this area, we need an adequate software infrastructure. In order to do so, we have proposed Continuum, an infrastructure based on service-oriented architecture (SOA), making use of framework and middleware, and employing a redefinition of follow-me semantics. In this redefined vision, users can go anywhere carrying the data and application they want, which they can use in a seamlessly integrated fashion with the real world. In this article, we focus on the description of the service-based architecture proposed for Continuum. The proposal widens the web services standards to support the mobility of services, allowing them to be deployed, copied, or moved. Besides, the abstraction provided enables the adaptation of legacy applications as Continuum pluggable services. We conduct some experimental analysis, using case study methodology. Based on these assessments, we present lessons learned and draw the conclusion of our work.

Keywords: software infrastructure, middleware, web services, service oriented architecture, ubiquitous computing.

MobSIP: A SIP extension to support application layer handover in realtime multimedia communications with mobility requirements

Daniel G. Costa — 2009-12-30

In real-time multimedia, the overall time in Internet communications must be low and constant, in order to keep real-time sense and received media quality. When mobility is a basic requirement, efficient and flexible solutions should be adopted, avoiding harming time sensitive applications. In order to support real-time multimedia communications with mobility requirements on Internet backbones, a novel SIP extension is proposed, adding direct support to handover procedures in SIP clients. The procedures of that new extension, MobSIP, are specified and implemented, allowing formal and experimental verifications.

Keywords: SIP, application layer mobility, handover procedures, real-time multimedia.

Letter from the Editor

Patricia Jaques — 2021-06-21