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Publications

2012

Controlling Hardware Synthesis with Aspects

Authors
Cardoso, JMP; Carvalho, T; Coutinho, JGF; Diniz, PC; Petrov, Z; Luk, W;

Publication
15th Euromicro Conference on Digital System Design, DSD 2012, Cesme, Izmir, Turkey, September 5-8, 2012

Abstract
The synthesis and mapping of applications to configurable embedded systems is a notoriously hard process. Tools have a wide range of parameters, which interact in very unpredictable ways, thus creating a large and complex design space. When exploring this space, designers must understand the interfaces to the various tools and apply, often manually, a sequence of tool-specific transformations making this an extremely cumbersome and error-prone process. This paper describes the use of aspect-oriented techniques for capturing synthesis strategies for tuning the performance of applications' kernels. We illustrate the use of this approach when designing application-specific architectures generated by a high-level synthesis tool. The results highlight the impact of the various strategies when targeting custom hardware and expose the difficulties in devising these strategies. © 2012 IEEE.

2012

The role of social networks in distributed informal information systems for innovation

Authors
Vasconcelos, V; Campos, P;

Publication
Organizational Integration of Enterprise Systems and Resources: Advancements and Applications

Abstract
Web 2.0 and Enterprise 2.0 concepts offer a whole new set of collaborative tools that allow new approaches to market research, in order to explore continuously and ever fast-growing social and media environments. Simultaneously, the exponential growth of online Social Networks, along with a combination of computer-based tools, is contributing to the construction of new kinds of research communities, in which respondents interact with researchers as well as with each other. Furthermore, by studying the networks, researchers are able to manage multiple data sources - user-generated contents. The main purpose of this paper is to propose a new concept of Distributed Informal Information Systems for Innovation that arises from the interaction of the accumulated stock of knowledge emerging at the individual (micro) level. A descriptive study unveils and reports when and how market research professionals use Social Networks for their work and therefore create distributed information systems for Innovation. © 2012, IGI Global.

2012

A framework to monitor clusters evolution applied to economy and finance problems

Authors
Oliveira, M; Gama, J;

Publication
INTELLIGENT DATA ANALYSIS

Abstract
The study of evolution has become an important research issue, especially in the last decade, due to our ability to collect and store high detailed and time-stamped data. The need for describing and understanding the behavior of a given phenomena over time led to the emergence of new frameworks and methods focused on the temporal evolution of data and models. In this paper we address the problem of monitoring the evolution of clusters over time and propose the MEC framework. MEC traces evolution through the detection and categorization of clusters transitions, such as births, deaths and merges, and enables their visualization through bipartite graphs. It includes a taxonomy of transitions, a tracking method based in the computation of conditional probabilities, and a transition detection algorithm. We use MEC with two main goals: to determine the general evolution trends and to detect abnormal behavior or rare events. To demonstrate the applicability of our framework we present real world economic and financial case studies, using datasets extracted from Banco de Portugal Central Balance-Sheet Database and the The Data Page of New York University -Leonard N. Stern School of Business. The results allow us to draw interesting conclusions about the evolution of activity sectors and European companies.

2012

Transmission of differential GPS signals over fiber for aircraft attitude determination

Authors
Pessoa, LM; Oliveira, JMB; Coelho, D; Castro, JCS; Salgado, HM; Fames, M;

Publication
2012 IEEE Avionics, Fiber- Optics and Photonics Technology Conference, AVFOP 2012

Abstract
The Daphne project has been addressing the adoption of an optical fiber infrastructure for future aircrafts. Beyond the obvious motivation of reduced weight and electromagnetic interference, the availability of a huge amount of bandwidth makes the optical fiber well suited to transport Radio Frequency (RF) signals transparently, while avoiding cumbersome dedicated RF cabling. An integrated optical network may be exploited to transport radio signals from diverse aircraft antennas ranging from satellite/earth communications, collision avoidance, GPS signals for positioning and attitude determination, weather/detection RADAR to corrosion sensors. Such network can also support passenger infotainment and mobile communication services, such as cellular GSM/UMTS/LTE, broadband Wi-Fi (IEEE 802.11) and Ultra-Wide-Band Wimedia/WiGig. Specifically, the optical fiber infrastructure may provide connectivity from external antennas (through remote nodes) to RF transceivers installed in the cockpit and avionics bay (head-end nodes); in the context of the present paper, the transmission of differential GPS signals used to provide aircraft attitude information will be discussed. The use of GPS for aircraft attitude determination has been under discussion for more than 20 years [1]. It consists in performing carrier-phase differential processing of measurements from GPS antennas affixed to the frame of the aircraft, which yields centimeter- or millimeter-level accuracies, provided that integer phase ambiguities are resolved [2]. The attitude algorithm consists in a highly accurate real time kinematic (RTK) technique, given the short baseline distance between antennas, in which the main antenna acts as a Base station and two auxiliary antennas as Rovers. In the present experiment, we used a setup consisting of two-antennas (Base and Rover), which is enough to evaluate the RTK performance. A particular aspect of concern stems from the fact that the transmission of optical signals through a complex optical fiber network is subject to the occurrence of reflections in the multitude of connectors spanning the path between a remote node and a head-end node. Therefore, we will focus our analysis on the performance impact of optical reflections affecting the power level stability of the optical source. © 2012 IEEE.

2012

Image Segmentation by Graph Partitioning

Authors
Torres, AS; Monteiro, FC;

Publication
NUMERICAL ANALYSIS AND APPLIED MATHEMATICS (ICNAAM 2012), VOLS A AND B

Abstract
In this paper we propose an hybrid method for the image segmentation which combines the edge-based, region-based and the morphological techniques in conjunction through the spectral based clustering approach. An initial partitioning of the image into atomic regions is set by applying a watershed method to the image gradient magnitude. This initial partition is the input to a computationally efficient region segmentation process which produces the final segmentation. We have applied our approach on several images of the Berkeley Segmentation Dataset. The results reveal the accuracy of the propose method.

2012

Schedulability Analysis of Sporadic Messages in the FlexRay Dynamic Segment

Authors
Lange, R; de Oliveira, RS; Bonet, E; Vasques, F;

Publication
2012 BRAZILIAN SYMPOSIUM ON COMPUTING SYSTEM ENGINEERING (SBESC 2012)

Abstract
FlexRay is a communication protocol heavily promoted as the future de facto standard for automotive systems. A major challenge associated with the design of FlexRay systems is the response time analysis of sporadic messages transmitted in the dynamic segment, a problem that has been shown to be a combinatorial problem. Although there are several methods available to make this analysis, they mainly rely on optimization techniques such as Integer Linear Programming (ILP), or use the Real-Time Calculus (RTC) framework. In this work we propose a method with pseudo-polynomial complexity to derive an upper bound for sporadic messages transmitted in the dynamic segment. We assess the performance of the proposed method comparing it with state-of-the-art methods available in the literature.

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