Branching points in the low-temperature dipolar hard sphere fluid

In this contribution, we investigate the low-temperature, low-density behaviour of dipolar hard-sphere (DHS) particles, i.e., hard spheres with dipoles embedded in their centre. We aim at describing the DHS fluid in terms of a network of chains and rings (the fundamental clusters) held together by branching points (defects) of different nature. We first introduce a systematic way of classifying inter-cluster connections according to their topology, and then employ this classification to analyse the geometric and thermodynamic properties of each class of defects, as extracted from state-of-the-art equilibrium Monte Carlo simulations. By computing the average density and energetic cost of each defect class, we find that the relevant contribution to inter-cluster interactions is indeed provided by (rare) three-way junctions and by four-way junctions arising from parallel or anti-parallel locally linear aggregates. All other (numerous) defects are either intra-cluster or associated to low cluster-cluster interaction energies, suggesting that these defects do not play a significant part in the thermodynamic description of the self-assembly processes of dipolar hard spheres. (C) 2013 AIP Publishing LLC.

Design and performance of a novel low-density parity-check code for distributed video coding

Low-density parity-check (LDPC) codes are nowadays one of the hottest topics in coding theory, notably due to their advantages in terms of bit error rate performance and low complexity. In order to exploit the potential of the Wyner-Ziv coding paradigm, practical distributed video coding (DVC) schemes should use powerful error correcting codes with near-capacity performance. In this paper, new ways to design LDPC codes for the DVC paradigm are proposed and studied. The new LDPC solutions rely on merging parity-check nodes, which corresponds to reduce the number of rows in the parity-check matrix. This allows to change gracefully the compression ratio of the source (DCT coefficient bitplane) according to the correlation between the original and the side information. The proposed LDPC codes reach a good performance for a wide range of source correlations and achieve a better RD performance when compared to the popular turbo codes.

Lubrificação de compressores que aspiram fluido frigorigéneo a temperaturas inferiores a -30° C

Trabalho Final de Mestrado para obtenção do grau de Mestre em Engenharia Mecânica

Self-assembly in chains, rings, and branches: a single component system with two critical points

Agências financiadoras: FCT - PEstOE/FIS/UI0618/2011; PTDC/FIS/098254/2008 ERC-PATCHYCOLLOIDS e MIUR-PRIN

As guardas de segurança para proteção a motociclistas: características e graus de eficácia

Os acidentes envolvendo veículos de duas rodas, são um dos maiores problemas da segurança rodoviária atual, no âmbito Europeu. Um dos tipos de acidentes que pode causar danos mais graves aos ocupantes desses veículos é o embate com guardas de segurança. Em consequência disso, neste trabalho foram desenvolvidas opiniões, abonatórias ou não, ao uso de dispositivos de proteção para motociclistas acoplados nas guardas de segurança. Estas opiniões vão partir de dados estatísticos, de estudos e exemplos concretos de vários autores e publicações relacionados com esta temática, sendo que o tipo de dispositivo de proteção para motociclistas que vai estar mais em foco e sendo ele o mais habitual nas estradas portuguesas será a saia metálica. Estes dispositivos de segurança para motociclistas ainda não são de uso obrigatório nas guardas de segurança na maioria dos países do continente Europeu, segundo a norma europeia EN 1317, apesar deste tipo de proteção já estar normalizada segundo padrões de lesões biomecânicos na zona da cabeça, cervical e anca/abdómen descritos na norma EN 1317 UNE 135900 – 1:2003, em alguns países é descurado o uso destas proteções, por não serem obrigatórias e porque ainda se tornam mais dispendiosas que as guardas de segurança habituais (barreiras de metal simples). Este estudo serviu essencialmente para verificar se estes dispositivos salvaguardam ou não a vida dos utilizadores de duas rodas, pois, se pelo contrário, aumentam ainda o risco, ou de lesões mais gravosas ou mesmo de morte, aquando o embate com as mesmas, os gastos associados a este tipo de equipamentos serão totalmente inúteis e desnecessários.

Check your biosignals here: a new dataset for off-person ECG biometrics

The Check Your Biosignals Here initiative (CYBHi) was developed as a way of creating a dataset and consistently repeatable acquisition framework, to further extend research in electrocardiographic (ECG) biometrics. In particular, our work targets the novel trend towards off-the-person data acquisition, which opens a broad new set of challenges and opportunities both for research and industry. While datasets with ECG signals collected using medical grade equipment at the chest can be easily found, for off-the-person ECG data the solution is generally for each team to collect their own corpus at considerable expense of resources. In this paper we describe the context, experimental considerations, methods, and preliminary findings of two public datasets created by our team, one for short-term and another for long-term assessment, with ECG data collected at the hand palms and fingers. (C) 2013 Elsevier Ireland Ltd. All rights reserved.