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Publications

2005

Enabling scalable inter-AS sign aling: a load reduction approach

Authors
Sofia, R; Guerin, R; Veiga, P;

Publication
10TH IEEE SYMPOSIUM ON COMPUTERS AND COMMUNICATIONS, PROCEEDINGS

Abstract
In order to achieve better scalability, inter-domain signaling protocols rely on aggregation to reduce the amount of state information that routers are required to maintain. Nonetheless, they do not address another scalability key factor the signaling load associated with establishing and maintaining reservations. Such load can be reduced if bandwidth is over-reserved. Over-reservation allows accommodating reservations without exchanging signaling messages, but may result in additional blocking. In this paper, we carry out a systematic investigation of the impact of over-reservation in different aggregation approaches, evaluating such impact in terms of the achieved signaling reduction, and blocking.

2005

Multi-objective evolutionary algorithm optimization of robotic manipulators

Authors
Pires, EJS; Oliveira, PBD; Machado, JAT;

Publication
Modelling and Simulation 2005

Abstract
The design of robotic manipulators considering both the structure and trajectory planning problems is addressed. These problems have been solved using either classical or metaheuristics optimization techniques considering single objectives. This paper proposes a multi-objective evolutionary algorithm to generate the robot structure and required manipulator trajectories. The proposed evolutionary algorithm is organized in a hierarchical form by using three genetic algorithms to optimize the initial, final and intermediate robotic configurations which are executed for each population member of top level multi-objective structure generator. The aim is to minimize the trajectory space ripple, the initial and final binary torques, while optimizing the mechanical structure. Simulations results are presented from solving a structure synthesis problem which considers the optimization of three simultaneous objectives.

2005

Discrimination of strain and temperature using Bragg gratings in microstructured and standard optical fibres

Authors
Frazao, O; Carvalho, JP; Ferreira, LA; Araujo, FM; Santos, JL;

Publication
MEASUREMENT SCIENCE & TECHNOLOGY

Abstract
In this work two sensing heads based on fibre Bragg grating structures are demonstrated, one for temperature independent measurement of strain and the other for simultaneous measurement of these two parameters. The first one relies on a single Bragg grating inscription in a microstructured optical fibre, resulting for two input orthogonal polarizations in two distinct resonance peaks with similar temperature sensitivities and different strain sensitivities. In the second structure two gratings were considered, one written in the same microstructured fibre and the other on a standard SMF fibre. Considerably different strain and temperature sensitivities were obtained for these two gratings, enabling simultaneous temperature and strain measurement with resolutions of +/- 1.5 degrees C and +/- 10.7 mu epsilon over a measurement range of 100 degrees C and 2000 mu epsilon, respectively.

2005

Time-Bounded Universal Distributions

Authors
Fortnow, L; Antunes, L;

Publication
Electronic Colloquium on Computational Complexity (ECCC)

Abstract

2005

Reverse Engineering of Framework Design using a Meta-Patterns-based Approach

Authors
Flores, N; Aguiar, A;

Publication
3RD ACS/IEEE INTERNATIONAL CONFERENCE ON COMPUTER SYSTEMS AND APPLICATIONS, 2005

Abstract
Object-oriented frameworks are a powerfitl reuse technique but they are also very complex and difficult to design. Framework's design aims at separating the invariant aspects across several applications in a domain - frozen spots - from the aspects that vary among applications and thus must be kept flexible and customizable - hot spots. The flexibility and extensibility provided at hot spots is usually achieved by following common design patterns, which are often hard and tiresome to identify without proper documentation. This paper proposes a reverse engineering approach to identify the design patterns used in a framework, using a high-level hot spot representation. The goals of this work include: researching a design approach that produces usable intermediate reuse information; defining a representation for design patterns based on meta-patterns; and developing a supporting tool to automate the reverse engineering process.

2005

Chirped Bragg grating fabricated in fused fibre taper for strain-temperature discrimination

Authors
Frazao, O; Melo, M; Marques, PVS; Santos, JL;

Publication
MEASUREMENT SCIENCE & TECHNOLOGY

Abstract
In this work, two sensing heads based on the fibre Bragg gratings written in fused biconical fibre taper for simultaneous measurement of temperature and strain are proposed. In the first configuration a comparison between a uniform Bragg grating and a grating written on a tapered fibre section, resulting in a chirp grating, is evaluated. The second sensing head consists of two gratings written in two different regions of the taper section. This fibre taper has a different geometry in each conical section, achieved by stretching the fibre at different velocities during the fabrication process. These two configurations are based on the different strain and similar temperature sensitivities of the Bragg gratings used to discriminate the two physical parameters. The performances are assessed and compared. The second structure presents good performance and more sensitivity, compared to the first sensing head.

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