ESTCB - Comunicações em encontros científicos e técnicos
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- Adaptive error control coding for a mobile broadband systemPublication . Torres, Paulo; Caseiro, Carlos; Gusmão, AntónioThe Mobile Broadband System (MBS) under research in Europoe aims at offering to mobile users an ATM-based radio access to the future integrated broadband communications network. It is well known that a high-quality transmission channel can be assumed within the fixed broadband network; however, this is far from being expected in the radio links of the future mobile system. This paper is concerned with the design of an error control coding scheme for a first stage of MBS implementation. The proposed scheme is a very flexible, hybrid one, which is based on the concatenation of a convolutional inner code, and a Reed-Solomon outer code, and combines ARQ and FEC features in an adaptive manner, under an implicit evaluation of the channel state. It is powerful enough to cope with poor channel conditions and is compatible with both ATM characteristics and those of a wide range of services (including required BER below lo-' with a delay of a few ms). A set of simulation results illustrates the advantages of the proposed error control coding scheme.
- Forest fire observation post in the infrared bandPublication . Covelo, Celso; Dionísio, Rogério Pais; Ribeiro, Luis Botelho; Ramos, FernandoThis paper describes a fully automated system for remote infrared and visible light detection and surveillance of forest fires. The project includes a set-up of a laboratory demonstrator. Topics such as image acquisition, automatic control and radiation levels detection are discussed.
- Slio-can based actuation system for greenhouse controlPublication . Metrôlho, J.C.M.M.This paper describes a system developed to implement the actuation after the data acquisition and processing from the plant. It was implemented over a previous developed CAN network, based on the 80C592 microcontroller from Philips implementing a hierarchical structure to form a tree topology. In this network a Personal Computer is connected through a Net Manager to units named Masters, located at the greenhouses, that allows the management of several secondary units named Slaves. This units are implemented using a SLIO (Serial Linked I/O device) from Philips, making possible the greenhouses control. This choice is due to the fact that the SLIO allows a cheaper solution to applications where no high speed requirements are needed such as the on/off functions. The assembling of the actuators within a greenhouse allows the use of an architecture whose communication is done through the main power cables. As mean of communication is used the CAN (Controller Area Network) protocol, which has a great flexibility and robustness needed in real-time control. The system, must allow easy expansion and configuration without compromising its performance. This is the case when the parameters must be changed whenever the weather conditions (Summer/Winter), force us to modify the setpoints of several control variables such as: temperature, light, humidity, among others.
- Applying matrix decomposition techniques to edge detection operatorsPublication . Sousa, Leonel; Salvado, JoséIn this paper decomposition techniques are applied to derivative operators, used for image edge detection. It is shown that the application of decomposition techniques to common edge detectors can result in substantial savings in computing time. For a 25x25 Laplacian of Gaussian, mask, an improvement of six times less arithmetic operations is achieved when decomposition techniques are applied.We also show that these techniques are advantageous for hardware realization of the filters. The memory required to a 2-D (nxn)-th order FIR filter direct realization with distributed arithmetic is O(2(n+1) ) while the worst case for the decomposed filter is O(n x 2n).
- Mitral valve contour extraction using active contour modelsPublication . Gonçalves, Paulo; Pinto, J.R. Caldas; Ramalho, Mário; Melo, J. Queiroz eTo perform mitral valve contour extraction a software application is presented to support the surgeon in the implant size decision. The system is based on the application, to mitral valve surgery images, of active contour models. First, current repair surgery to mitral valve disease is discussed. Active contour models are presented and using different implementation approaches a comparison was done. The algorithms proposed by Kass, Amini, Cohen, Eviatar and Shah (Greedy algorithm) were implemented in test environment. The implementation to be used in the software application, is the one due to Kass with a few modifications related to Cohen’s approach. During surgery, the system needs to be calibrated and the active contour initialised. These processes are supported by a colour segmentation technique, tested with real images, using fuzzy sets. Real open-heart surgery images have been used to test the system developed.
- Development system for FPGA-based digital circuitsPublication . Sklyarov, Valery; Fonseca, José A.; Monteiro, Ricardo; Oliveira, Arnaldo; Melo, Andreia; Lau, Nuno; Skliarova, Iouliia; Neves, Paulo Alexandre; Ferrari, AntónioThe paper discusses some new hardware and software tools that can be used for the design of virtual circuits based on dynamically reconfigurable FPGAs. With the aid of these tools we can implement a system that requires some hardware resources Rc, on available hardware that has resources Rh, where Rc>Rh. The main idea of the approach supported by these tools is the rational combination of FPGA capabilities with some proposed methods for producing a modifiable specification, together with a novel technique for architectural and logic synthesis, which has been incorporated into the new design environment.
- FPGA: targeted development system for embedded applicationsPublication . Sklyarov, Valery; Fonseca, José A.; Monteiro, Ricardo; Oliveira, Arnaldo; Melo, Andreia; Lau, Nuno; Kondratjuk, Konstantin; Skliarova, Iouliia; Neves, Paulo Alexandre; Ferrari, AntónioThis paper considers approaches to the design and implementation of embedded systems using XC6200 FPGAs. The methods that are introduced enable the synthesis of circuits that are modifiable and extensible, and that provide a virtual function capability. The accepted behavioral specification supports modularity and hierarchy. The developed design tools allow translating this specification into dynamically modifiable control circuits. A method based on reconfigurable cores for rapid design of reconfigurable virtual datapath was suggested. A stand-alone board using one XC6216 FPGA was designed and two other solutions, currently under development, were discussed. They can be used as virtual embedded controllers. An integrated design environment (IDELS) has been developed to provide specification, synthesis, simulation, testing, debugging, and implementation of the circuits in hardware. The software has been developed using Visual C++ and allows access to both stand-alone and built-in PC boards.
- Materiais xistosos: aplicabilidade em pavimentos rodoviáriosPublication . Luzia, Rosa; Santos, Luís Picado; Quaresma, LuísNeste estudo faz-se a caracterização, geotécnica e do comportamento mecânico, de dois materiais xistosos, pertencentes ao "Complexo Xisto-Graváquico", recolhidos no troço Raiva-Catraia dos Poços do Itinerário Complementar 7 (IC7) da rede rodoviária nacional, tendo como finalidade analisar a sua aplicabilidade em fundação e nas camadas granulares de pavimentos rodoviários. Procede-se ainda à análise dos resultados daquela caracterização a partir de um conjunto de especificações e recomendações Portuguesas, Francesas e Norte Americanas.
- Flexible time-triggered protocol for CAN: new scheduling and dispatching solutionsPublication . Fonseca, José A.; Martins, Ernesto V.; Almeida, L.; Pedreiras, P.; Neves, Paulo AlexandreOne of the possibilities to build robust communication systems with respect to their temporal behaviour is to use autonomous control based on the time-triggered paradigm. The FTT-CAN - flexible time-triggered protocol, relies on centralised scheduling but makes use of the CAN native distributed arbitration to reduce communication overhead. There, a planning scheduler is used within a master node to reduce the scheduling run-time overhead. On-line changes to the communication requirements can then be made under guaranteed timeliness. In addition FTT-CAN also allows an efficient combination of both time-triggered and event- triggered traffic with temporal isolation. In this paper, recent evolutions of the initial protocol definition concerning transmission of synchronous and asynchronous messages are presented. These consist in a time division of the elementary transmission window which optimises the available bandwidth for asynchronous messages, keeping the timeliness of synchronous messages without jeopardising their transmission jitter. A novel solution for the planning scheduler is also presented. It consists in an FPGA-based coprocessor which implements the planning scheduler technique without imposing overhead to the arbiter CPU. With it, it is possible to reduce strongly the plan duration thus allowing on-line admission demanded by system elements and, also, to extend the protocol application to high-speed networks.
- Resistência à fadiga de juntas soldadas reabilitadas por refusão TIG e plasmaPublication . Ramalho, Armando; Ferreira, J.A.M.; Branco, C.M.Resumo. As técnicas de refusão do pé do cordão de soldadura por TIG e plasma são frequentemente usadas para aumentar a resistência e a fiabilidade de peças solicitadas à fadiga. Neste trabalho apresentam-se resultados de um estudo de investigação sobre a utilização destas técnicas na recuperação da resistência à fadiga de juntas soldadas em T solicitadas por flexão em três pontos. As juntas são fabricadas em aço St 52 – 3 e obtidas por soldadura com eléctrodo revestido. São estudadas quatro situações: juntas não tratadas, juntas tratadas por refusão TIG, juntas pré-fissuradas e posteriormente tratadas por refusão TIG e juntas pré-fissuradas e posteriormente tratadas por refusão plasma. A eficiência dos tratamentos de refusão TIG e plasma na reabilitação da resistência à fadiga é analisada e discutida com base nos resultados de fadiga e em elementos complementares determinados durante a investigação, tais como: o perfil do pé dos cordões, a microestrutura e os perfis de dureza nas regiões soldada e afectada térmicamente e dos defeitos detectados no cordão. A eficiência obtida pelo processo de refusão por plasma é bastante satisfatória e muito superior à da refusão por TIG.