2012
Authors
Marau, R; Behnam, M; Iqbal, Z; Silva, P; Almeida, L; Portugal, P;
Publication
IEEE International Workshop on Factory Communication Systems - Proceedings, WFCS
Abstract
Recent trends in distributed embedded systems, such as those found in avionics and trains, have shown an increase in the amount and heterogeneity of the information that needs to be exchanged, together with a growing importance of supporting dynamic reconfiguration and adaptive behaviors. In this paper we focus on Ethernet technologies with real-time reconfiguration support and we address the case of middle-size networking infrastructures with a few switches. We use the FTT-SE protocol with the needed adaptations to support dynamic heterogeneous real-time transactions in multi-hop networks. The paper presents a worst-case response-time analysis that provides timeliness guarantees, improving the results obtained with another previous analysis, decreasing the needed network capacity for guaranteed schedulability by 25% on average. Practical experiments and simulation results validate the proposed approach and analysis. © 2012 IEEE.
2012
Authors
Barbosa, SM; Madsen, KS;
Publication
GEODESY FOR PLANET EARTH: PROCEEDINGS OF THE 2009 IAG SYMPOSIUM
Abstract
The quantification of the long-term variability of relative sea-level is a fundamental problem in geodesy. In the present study, quantile regression is applied for characterising the long-term variability in relative sea-level at the Gedser and Hornbaek tide gauges, in the North Sea-Baltic Sea transition zone. Quantile regression allows to quantify not only the rate of change in mean sea-level but also in extreme heights, providing a more complete description of long-term variability. At Gedser the lowest relative heights are increasing at a rate approximately 40% higher than the mean rate, while at Hornbaek the relative sea-level slopes are stable across most of the quantiles. A 30-year running window analysis shows that the linear trends display considerable decadal variability over the twentieth century for both stations.
2012
Authors
Paulo, J; Reis, P; Pereira, J; Sousa, A;
Publication
Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics)
Abstract
Deduplication is widely accepted as an effective technique for eliminating duplicated data in backup and archival systems. Nowadays, deduplication is also becoming appealing in cloud computing, where large-scale virtualized storage infrastructures hold huge data volumes with a significant share of duplicated content. There have thus been several proposals for embedding deduplication in storage appliances and file systems, providing different performance trade-offs while targeting both user and application data, as well as virtual machine images. It is however hard to determine to what extent is deduplication useful in a particular setting and what technique will provide the best results. In fact, existing disk I/O micro-benchmarks are not designed for evaluating deduplication systems, following simplistic approaches for generating data written that lead to unrealistic amounts of duplicates. We address this with DEDISbench, a novel micro-benchmark for evaluating disk I/O performance of block based deduplication systems. As the main contribution, we introduce the generation of a realistic duplicate distribution based on real datasets. Moreover, DEDISbench also allows simulating access hotspots and different load intensities for I/O operations. The usefulness of DEDISbench is shown by comparing it with Bonnie++ and IOzone open-source disk I/O micro-benchmarks on assessing two open-source deduplication systems, Opendedup and Lessfs, using Ext4 as a baseline. As a secondary contribution, our results lead to novel insight on the performance of these file systems. © 2012 Springer-Verlag.
2012
Authors
Brandao, D; Martins, N; Alvelos, H;
Publication
DESIGN JOURNAL
Abstract
In this paper we will maintain that cultural institutions are increasingly facing the inevitability of a profound revision in their traditional parameters of unidirectional communication. Given the increasing availability of tools for audiovisual production as well as the diversity of networked communication contexts, the roles of the user and the audience have come to assume a participatory potential in the content they consume and attend; this will dictate their repositioning in relation to the universe of institutions' work. In order to communicate new messages, media narratives, views or perspectives on the same reality are constantly constructed, deconstructed and reconstructed. In this age of 'Consumer-Generated Media', identities and representations are constantly changing. The idea and the concept of a brand now extends far beyond its own limits, taking on important emotional values, and people enjoy being a part of that brand's mythology. The Serralves Foundation, along with its Museum of Contemporary Art, in Porto, Portugal, was the subject of a first study of an empirical nature: a series of audio-visual objects were developed, in order to generate material for analysis and proposition. In this subsequent stage, we aim at the identification of new procedures and practices that may be effectively implemented within the institutional universe. We intend to establish more efficient communication contexts, including the maximizing of a set of relationships between institutions and audiences regarding dimensions that are traditionally outside the institutional radar: identity, narrative and affection. By referring to key examples, we will posit that in order to achieve more success in their missions, cultural institutions should focus on participatory education and communication processes regarding contemporary issues. By doing this, they will strengthen their engagement with their audiences and bring them into the institutions' projects. This project is currently undertaking a wide inventory and taxonomy of the various institutional paradigms in regards to communication practices. We aim at producing a map of vocations and positions within the institutional world in regards to the aforementioned issues that require participatory communication.
2012
Authors
Vide, PC; Barbosa, FM; Carvalho, JB;
Publication
Proceedings of 9th International Conference, ELEKTRO 2012
Abstract
With the development of synchronized phasor measurement technology in recent years, it gains great interest the use of PMU measurements to improve state estimation performances. In this paper, a mixed measurement (SCADA and PMU measurements) state estimator is proposed. Several measures useful for evaluating various aspects of the performance of the mixed measurement state estimator are proposed and explained. State Estimator validity, performance and characteristics of the results on IEEE 14 bus test system are presented. © 2012 IEEE.
2012
Authors
Valle, OT; Milack, AV; Montez, C; Portugal, P; Vasques, F;
Publication
IEEE International Workshop on Factory Communication Systems - Proceedings, WFCS
Abstract
One of the motivations for use of wireless sensor networks (WSNs) in industrial environments is related to the reduced deployment and maintenance costs, when compared to the use of wired networks for connecting single I/O points. Nevertheless, a well-known problem for the use of wireless communication in industrial environments is related to the unreliable nature of the communication medium. Therefore, the search for communication reliability in WSNs is a relevant topic of research for the scientific community. In this paper we propose an innovative message retransmission scheme, based on network coding techniques, to increase the reliability of message exchanges in industrial environments. The proposed technique: NetCod, that improve the probability of message deliver by allowing the message retransmission whenever a loss occurs is experimentally compared with state of the art techniques: BlockACK, Redundant TDMA and Master/Slave. A comparative experimental assessment of these four techniques was performed using MicaZ motes. Metrics such as: message loss, message transmission delay and power consumption were used to comparatively assess the behavior of these retransmission techniques. © 2012 IEEE.
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