my latest work entitled Second Order Swarm Intelligence with Vitorino Ramos and Jorge Louçã will be presented at the HAIS’2013 Conference in Salamanca, latter this year. It is an exploration of Ant Colony Systems by introducing a second order feedback mechanism. This is done with a negative pheromone that acts as a `non-entry’ signal.
An artificial Ant Colony System (ACS) algorithm to solve general-purpose combinatorial Optimization Problems (COP) that extends previous AC models  by the inclusion of a negative pheromone, is here described. Several Travelling Salesman Problem (TSP) were used as benchmark. We show that by using two different sets of pheromones, a second-order co-evolved compromise between positive and negative feedbacks achieves better results than single positive feedback systems. The algorithm was tested against known NP-complete combinatorial Optimization Problems, running on symmetrical TSP’s. We show that the new algorithm compares favourably against these benchmarks, accordingly to recent biological findings by Robinson [26,27], and Gruter  where “No entry” signals and negative feedback allows a colony to quickly reallocate the majority of its foragers to superior food patches. This is the first time an extended ACS algorithm is implemented with these successful characteristics.
PDF available from arXiv
NETWORK ANALYSIS OF SOCIAL AND DIGITAL MEDIA 47th HAWAII INTERNATIONAL CONFERENCE ON SYSTEM SCIENCES (HICSS) Minitrack: Network Analysis of Social and Digital Media Track: Digital and Social Media Conference: JANUARY 6-9, 2014 http://www.hicss.hawaii.edu/ Multilevel innovation networks PDW 2013 Academy of Management Meetings; Orlando, FL, USA Friday, Aug 9 2013 3:00PM – 7:00PM at WDW Swan [...]
As I’m starting a new life in the UK I need to adapt to some things, but… YES BUT… We always believe that we have our little shenanigans and mischiefs in Portugal, mainly with computers. The Portuguese Computer layout, although “international” has been changed to include accents, and moving some programer keys to places that [...]
Segundo o relatório para a transparência publicado da EFF (Eletronic Frontier Foundation), Portugal aparece logo em segundo lugar na lista de países que mais pedem a identificação de contas de utilizadores ao Google. Agora poderíamos pensar à primeira vista que este tipo de situação seria pedida por países de democracias dúbias ou onde a própria [...]
When doing community detection on networks, sometimes we have more than connections between entities. These entities represent something in reality that we might want to represent also in the network visualisation. Consider the following example extracted from the Nexus repository library(igraph) gg <- nexus.get("Davis") plot(gg) I’m using the Davis Dataset. This is the dataset collected [...]
E agora para algo completamente diferente do que por aqui aparece, a BMW lançou um vídeo dos seus icónicos 90 anos a produzir motociclos. Já devem ter percebido que por aqui há uma crise de meia idade a nascer, mas mais pormenores para outras alturas.