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Publications

2016

Exploiting universal redundancy

Authors
Shoker, A;

Publication
15th IEEE International Symposium on Network Computing and Applications, NCA 2016, Cambridge, Boston, MA, USA, October 31 - November 2, 2016

Abstract
Fault tolerance is essential for building reliable services; however, it comes at the price of redundancy, mainly the 'replication factor' and 'diversity'. With the increasing reliance on Internet-based services, more machines (mainly servers) are needed to scale out, multiplied with the extra expense of replication. This paper revisits the very fundamentals of fault tolerance and presents 'artificial redundancy': a formal generalization of 'exact copy' redundancy in which new sources of redundancy are exploited to build fault tolerant systems. On this concept, we show how to build 'artificial replication' and design 'artificial fault tolerance' (AFT). We discuss the properties of these new techniques showing that AFT extends current fault tolerant approaches to use other forms of redundancy aiming at reduced cost and high diversity. © 2016 IEEE.

2016

An allocation scheme for IEEE 802.15.4-ZigBee cluster-tree networks

Authors
Leão, E; Vasques, F; Portugal, P; Moraes, R; Montez, C;

Publication
IECON 2016 - 42nd Annual Conference of the IEEE Industrial Electronics Society, Florence, Italy, October 23-26, 2016

Abstract

2016

Photocatalytic oxidation of Reactive Black 5 with UV-A LEDs

Authors
Ferreira, LC; Lucasa, MS; Fernandes, JR; Tavares, PB;

Publication
JOURNAL OF ENVIRONMENTAL CHEMICAL ENGINEERING

Abstract
The effectiveness of UV-A Light emitting diodes (UV-A LEDs) for decolourization of Reactive Black 5 (RB5) solutions in a continuous photoreactor and the effect of different operational parameters on the photocatalytic decolourization of RB5 were investigated in the present work. The operational parameters included catalyst load, initial dye concentration, irradiance and solution flowrate. Photocatalytic experiments were conducted in a self-designed photoreactor with a matrix of 96 UV-A LEDs (375 nm) and Evonik P-25 TiO2 was used as a photocatalyst. The optimum experimental conditions that allowed the highest decolourization of RB5 (89%) were an irradiance of 40 W/m(2), 1.0 g/L of TiO2, 50 mg/L of RB5 and a flowrate of 0.8 mL/min. A continuous stirred tank reactor (CSTR) design equation, subsequently simplified to a pseudo-first order rate equation, was used to analyse the kinetics of the experimental results. From the kinetics it is possible to observe that high TiO2 concentrations (1.0 g/L) and light irradiances (40 W/m(2)) positively affect the reaction rate (r, 2.483 x 10 (7) mol/L min) and the reaction rate constants (k, 7.351 x 10 (3) min (1)). The figure-of-merit electrical energy per order (E-EO) was calculated for the photoreactor, and values of 220 kWh/m(3)/order were reached for an electric power consumption of 0.0129 kW and a solution flowrate of 4.8 x 10 (6)m(3)/h. Results demonstrated that a UV-A LED/TiO2 process can effectively decolourize RB5 dye solutions within the selected optimum conditions.

2016

A method for rigorous design of reconfigurable systems

Authors
Madeira, A; Neves, R; Barbosa, LS; Martins, MA;

Publication
SCIENCE OF COMPUTER PROGRAMMING

Abstract
Reconfigurability, understood as the ability of a system to behave differently in different modes of operation and commute between them along its lifetime, is a cross-cutting concern in modern Software Engineering. This paper introduces a specification method for reconfigurable software based on a global transition structure to capture the system's reconfiguration space, and a local specification of each operation mode in whatever logic (equational, first-order, partial, fuzzy, probabilistic, etc.) is found expressive enough for handling its requirements. In the method these two levels are not only made explicit and juxtaposed, but formally interrelated. The key to achieve such a goal is a systematic process of hybridisation of logics through which the relationship between the local and global levels of a specification becomes internalised in the logic itself.

2016

The Effectiveness of Query Expansion when searching for Health related Content: InfoLab at CLEF eHealth 2016

Authors
Silva, R; Lopes, CT;

Publication
Working Notes of CLEF 2016 - Conference and Labs of the Evaluation forum, Évora, Portugal, 5-8 September, 2016.

Abstract
In this paper we describe the participation of InfoLab in the patient-centred information retrieval task of the CLEF eHealth 2016 lab. We analyse the performance of several query expansion strategies using difierent sources of terms and difierent methods to select the terms to be added to the original query. One of the strategies uses pseudo relevance feedback for term selection. The other strategies use external sources such as Wikipedia articles and definitions from the UMLS Metathesaurus for term selection. In the end, readability metrics such as SMOG, FOG and Flesch-Kincaid were used to re-rank the documents retrieved using the expanded queries. As the relevance and readability assessments are not available we can't make any conclusion regarding the results of our approaches.

2016

SSA-based MATLAB-to-C compilation and optimization

Authors
Reis, L; Bispo, J; Cardoso, JMP;

Publication
Proceedings of the 3rd ACM SIGPLAN International Workshop on Libraries, Languages, and Compilers for Array Programming, ARRAY@PLDI 2016, Santa Barbara, CA, USA, June 14, 2016

Abstract
Many fields of engineering, science and finance use models that are developed and validated in high-level languages such as MATLAB. However, when moving to environments with resource constraints or portability challenges, these models often have to be rewritten in lower-level languages such as C. Doing so manually is costly and error-prone, but automated approaches tend to generate code that can be substantially less efficient than the handwritten equivalents. Additionally, it is usually difficult to read and improve code generated by these tools. In this paper, we describe how we improved our MATLAB-to-C compiler, based on the MATISSE framework, to be able to compete with handwritten C code. We describe our new IR and the most important optimizations that we use in order to obtain acceptable performance. We also analyze multiple C code versions to identify where the generated code is slower than the handwritten code and identify a few key improvements to generate code capable of outperforming handwritten C. We evaluate the new version of our compiler using a set of benchmarks, including the Disparity benchmark, from the San Diego Vision Benchmark Suite, on a desktop computer and on an embedded device. The achieved results clearly show the efficiency of the current version of the compiler. Copyright is held by the owner/author(s). Publication rights licensed to ACM.

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