2,864 research outputs found
Texture descriptor combining fractal dimension and artificial crawlers
Texture is an important visual attribute used to describe images. There are
many methods available for texture analysis. However, they do not capture the
details richness of the image surface. In this paper, we propose a new method
to describe textures using the artificial crawler model. This model assumes
that each agent can interact with the environment and each other. Since this
swarm system alone does not achieve a good discrimination, we developed a new
method to increase the discriminatory power of artificial crawlers, together
with the fractal dimension theory. Here, we estimated the fractal dimension by
the Bouligand-Minkowski method due to its precision in quantifying structural
properties of images. We validate our method on two texture datasets and the
experimental results reveal that our method leads to highly discriminative
textural features. The results indicate that our method can be used in
different texture applications.Comment: 12 pages 9 figures. Paper in press: Physica A: Statistical Mechanics
and its Application
Complex network classification using partially self-avoiding deterministic walks
Complex networks have attracted increasing interest from various fields of
science. It has been demonstrated that each complex network model presents
specific topological structures which characterize its connectivity and
dynamics. Complex network classification rely on the use of representative
measurements that model topological structures. Although there are a large
number of measurements, most of them are correlated. To overcome this
limitation, this paper presents a new measurement for complex network
classification based on partially self-avoiding walks. We validate the
measurement on a data set composed by 40.000 complex networks of four
well-known models. Our results indicate that the proposed measurement improves
correct classification of networks compared to the traditional ones
Adulterants found in mixtures of illegal psychoactive drugs
Os danos biológicos causados pelo uso de substâncias psicoactivas ilegais podem resultar não só das substâncias
ilegais por si só, mas também da presença de substâncias que os traficantes lhes adicionam no sentido de aumentar
o volume final de droga (substâncias de corte). O objectivo central do presente estudo consistiu na análise de substâncias
psicoactivas ilegais e dos seus contaminantes/adulterantes, pela conjugação de esforços entre CHECK-IN/
APDES e o Instituto Nacional de Medicina Legal do Porto. Esta colaboração permitiu comparar dados portugueses
com os dados gerados pelo projecto Energy Control em Espanha, que se tem dedicado desde há mais de 10 anos Ã
redução de riscos.
The biological damages caused by the use of illicit psychoactive substances can result not only from the illegal
substances themselves, but can also be due to substances that dealers had to the mixtures in order to increase the
overall volume of drug (cutting substances). The central aim of the present study was analysing illegal psychoactive
substances and their contaminants/adulterants, through the conjugation of efforts by CHECK-IN/APDES and Instituto
Nacional de Medicina Legal do Porto. This cooperation allowed the comparison of Portuguese data with the data that
were collected in Spain by Energy Control, a project that has been working in risk reduction for the past 10 years
Three-winding transformer with DC microgrid and active power filter
Trabalho final de Mestrado para obtenção do grau de Mestre em Engenharia Eletrotécnica Ramo Automação e Eletrónica IndustrialEsta tese procura estudar uma nova arquitetura para postos de transformação. Estes são, na grande maioria dos casos, constituÃdos por transformadores de apenas dois enrolamentos (entrada e saÃda) e, por essa razão, a implementação de microrredes DC requere planeamento e dimensionamento extra. Este trabalho procura criar um dispositivo que facilite a interligação de postos de transformação com microrredes DC. Este dispositivo é composto por dois componentes principais: Um transformador de três enrolamentos – em vez do transformador de dois enrolamentos clássico, usualmente usado nos postos de transformação; um conversor AC/DC bidirecional que interliga a microrrede DC com o transformador. A ideia é que tanto o primário, como o secundário do transformador estão ligados como normalmente encontrado nos postos de transformação – a potência flui da rede para a carga – enquanto o terciário está ligado a ao conversor AC/DC (microrrede). Como referido anteriormente, o conversor é bidirecional o que significa que este pode direcionar a potência para o sistema (e.g.: veÃculo-para-X) ou para o microrrede (e.g.: carregamento de um veÃculo elétrico). Adicionalmente, o conversor também funciona como filtro ativo de potência, suavizando a potência reativa e o conteúdo harmónico presente na rede, gerado pelas cargas.This thesis takes a different approach to the classic distribution transformer topology. These transformers usually contain only two windings (input and output) and, for this reason, the addition of DC microgrids onto them requires additional planning and designing. This work aims to create a device in which a DC microgrid can be seamlessly integrated into the system. This device would be composed by two main components: A three-winding transformer – instead of the classical two-winding transformer used in typical distribution transformers. A bi-directional AC/DC converter which function is to interface between the DC microgrid and the transformer. The idea is that both primary and secondary windings of the transformer work as commonly known in a distribution transformer – power flows from the grid to the loads – while the terciary winding interconnects the AC/DC converter to the system. As mentioned above, the converter is bi-directional which means it can direct the power to the system itself (e.g.: vehicle-to-X topology) or to the DC microgrid (e.g..charging an electric vehicle). Furthermore, the converter is also capable of working as an active power filter, softening the reactive power and harmonic content present in the grid, which is generated by the loads.N/
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