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Publicações

2016

Analysis of J-Pole Antenna Configurations for Underwater Communications

Autores
Aboderin, O; Inacio, SI; Santos, HM; Pereira, MR; Pessoa, LM; Salgado, HM;

Publicação
OCEANS 2016 MTS/IEEE MONTEREY

Abstract
The capability of relatively high-speed short-range communications of Autonomous Underwater Vehicles (AUVs) in underwater scenarios, for example, for communication between vehicles or when the AUV is approaching a docking station for downloading of data gathered during a survey mission, is becoming a relevant application in the context of sea exploration and mining. In this paper the analysis of the J-pole antenna and two of its configurations namely Super J-pole and Collinear J-pole antennas are presented, aimed at improving the propagation distance and data rates when such antennas are installed on AUV for onward usage in underwater communications. The performance of these three antennas is assessed through simulation in fresh and sea water, operating in the High Frequency (HF) band. These antennas are compared in terms of bandwidth and directivity which are important elements in the transmission and reception of electromagnetic signals. The results obtained show that these antennas will be desirable both for improved data rates and propagation distance in fresh and sea water. The antennas were designed with FEKO electromagnetic simulation software.

2016

Declarative Coordination of Graph-based Parallel Programs

Autores
Cruz, F; Rocha, R; Goldstein, SC;

Publicação
ACM SIGPLAN NOTICES

Abstract
Declarative programming has been hailed as a promising approach to parallel programming since it makes it easier to reason about programs while hiding the implementation details of parallelism from the programmer. However, its advantage is also its disadvantage as it leaves the programmer with no straightforward way to optimize programs for performance. In this paper, we introduce Coordinated Linear Meld (CLM), a concurrent forward-chaining linear logic programming language, with a declarative way to coordinate the execution of parallel programs allowing the programmer to specify arbitrary scheduling and data partitioning policies. Our approach allows the programmer to write graph-based declarative programs and then optionally to use coordination to fine-tune parallel performance. In this paper we specify the set of coordination facts, discuss their implementation in a parallel virtual machine, and show-through example-how they can be used to optimize parallel execution. We compare the performance of CLM programs against the original uncoordinated Linear Meld and several other frameworks.

2016

On Routing Flexibility of Wormhole-Switched Priority-Preemptive NoCs

Autores
Nikolic, B; Pinho, LM; Indrusiak, LS;

Publicação
2016 IEEE 22ND INTERNATIONAL CONFERENCE ON EMBEDDED AND REAL-TIME COMPUTING SYSTEMS AND APPLICATIONS (RTCSA)

Abstract
Flit-level preemptions via virtual channels have been proposed as one viable method to implement priority-preemptive arbitration policies in NoC routers, and integrate NoCs in the hard real-time domain. In recent years, researchers have explored several aspects of priority-preemptive NoCs, such as different arbitration techniques, different priority assignment methods (where applicable) and different workload mapping approaches, all with the common objective to use interconnect mediums more efficiently. Yet, the impact of different routing techniques on such a model is still an unexplored topic. Motivated by this reality, in this work we study the effects of routing flexibility on wormhole-switched priority-preemptive NoCs.

2016

Multimodal Interaction Robotic Devices in a Simulated Environment

Autores
Faria, BM; Dias, D; Reis, LP;

Publicação
2016 11TH IBERIAN CONFERENCE ON INFORMATION SYSTEMS AND TECHNOLOGIES (CISTI)

Abstract
This work aimed developing a multimodal interaction platform of robotic devices in a simulated environment. It was developed and implemented a system that allow a user to interact with an Intelligent Wheelchair (IW) allowing to test the robot driving control through an adaptive multimodal interface. Furthermore, it was implemented and tested a robot representing a ramp for Paralympic sport "Boccia". This Intelligent Robotic Ramp (IRR) will allow practitioners with various physical and psychological disorders, to practice this sport in a more autonomous way. This IRR will have greater emphasis on the BC3 category, where its practitioners have a very high level of dependency, having the need to resort to his coach and a launch pad (ramp) in order to play the game.

2016

Robust CDM and Pole Placement PID Based Thrust Controllers for Multirotor Motor-Rotor Simplified Model

Autores
Giernacki, W; Horla, D; Sadalla, T; Coelho, JP;

Publicação
2016 INTERNATIONAL SIBERIAN CONFERENCE ON CONTROL AND COMMUNICATIONS (SIBCON)

Abstract
Positioning and orientation precision of a multirotor aerial robot can be increased by using additional control loops for each of the driving units. As a result, one can eliminate lack of balance between true thrust forces. A control performance comparison of two proposed thrust controllers, namely robust controller designed with coefficient diagram method (CDM) and proportional, integral and derivative (PID) controller tuned with pole-placement law, is presented in the paper. The research has been conducted with respect to model/plant matching uncertainty and with the use of anti-windup compensators for a simple motor-rotor model approximated by first-order inertia plus delay. From the obtained simulation results one concludes that appropriate choice of AWC compensator improves tracking performance and increases robustness against parametric uncertainty.

2016

[INVITED] New advances in fiber cavity ring-down technology

Autores
Silva, SO; Magalhaes, R; Marques, MB; Frazao, O;

Publicação
OPTICS AND LASER TECHNOLOGY

Abstract
A brief review in the cavity ring-down technique (CRD) is presented. In this review, there will only be considered the conventional fiber CRD configuration, i.e., there will only be presented researches involving cavities with two couplers with 99:1 ratios, due to the large amount of publications involving this spectroscopy method. The presented survey is divided in different topics related to the measurement of physical parameters, such as strain and temperature, curvature, pressure, refractive index, gas and biochemical sensing.

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