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Miranda V.,INESC TEC | Miranda V.,University of Porto | Castro A.R.G.,Federal University of Pará | Lima S.,Federal University of Maranhão
IEEE Transactions on Power Delivery | Year: 2012

This paper presents a new approach to incipient fault diagnosis in power transformers, based on the results of dissolved gas analysis. A set of autoassociative neural networks or autoencoders is trained, so that each becomes tuned with a particular fault mode or no fault condition. The scarce data available forms clusters that are densified using an Information Theoretic Mean Shift algorithm, allowing all real data to be used in the validation process. Then, a parallel model is built where the autoencoders compete with one another when a new input vector is entered and the closest recognition is taken as the diagnosis sought. A remarkable accuracy of 100% is achieved with this architecture, in a validation data set using all real information available. © 2012 IEEE.


Cota M.P.,University of Vigo | Thomaschewski J.,Emden Leer University of Applied Sciences | Schrepp M.,SAP | Goncalves R.,INESC TEC
Procedia Computer Science | Year: 2013

For the international use of software products it is important to know the culture, language and behavior of the citizens. Means: internationalization and location. To be able to evaluate these products it is significant to know how people from a country behave and express their feelings. This article presents a questionnaire which was initially developed in German, English and Spanish and is now available after a complex transformation in Portuguese. © 2013 The Authors. Published by Elsevier B.V.


Pinto J.P.,INESC TEC | Viana P.,Polytechnic Institute of Porto
ACM International Conference Proceeding Series | Year: 2015

This short paper presents a game for collecting metadata to describe video content. Tags, introduced by registered players on a given timecode of the video, are collected and validated based on a collaborative scoring mechanism that excludes erratic annotations. The system follows a gamification approach for motivating users and includes processes for semantically relating concepts. © 2015 ACM.


Lima S.L.,Federal University of Maranhão | Saavedra O.R.,Federal University of Maranhão | Miranda V.,INESC TEC | Miranda V.,University of Porto
IEEE Transactions on Power Delivery | Year: 2015

Power transformers are important equipment of a substation from the generation, transmission, and distribution of electricity to end users. The costs associated with purchasing a power transformer in the voltage class of 500 kV (100 MVA) are a few million. The fines imposed by regulatory agencies are significant when there is unavailability of equipment for any defect or failure. Therefore, energy companies have been struggling in preventive and predictive maintenance in order to maintain this equipment in an effective maintenance program, avoiding the occurrence of failures. There are various techniques that are utilized for diagnosis and analysis of transformer failure, but little has been discussed about mechanisms that assist in decision making when it is necessary to overload the transformer, especially in emergency situations. In this paper, we present a framework that unifies the step of fault diagnosis of power transformers with the process of decision making, considering the current operating conditions as well as the life of the equipment. The assistance to the decision-making methodology is based on risk analysis with indicators derived from the failure rate and Arrhenius theory. The validation of the method is performed with a case study using data from a utility. © 1986-2012 IEEE.


Conceicao S.,INESC Porto | Ribeiro F.,INESC TEC | Campos R.,INESC TEC | Ricardo M.,INESC Porto
IFIP Wireless Days | Year: 2015

Wireless Underground Networks (WUNs) include communications links between buried nodes and between buried and aboveground nodes. WUNs have many applications, such as border surveillance, agriculture monitoring, and infrastructure monitoring. Recent studies have shown that they are feasible and have deployment advantages over wired networks. Yet, so far WUNs evaluations have been done using testbeds only, and a tool enabling simulations on TCP/IP WUNs is lacking. We propose a simulator of TCP/IP wireless underground networks based on ns-3. The simulator was validated against experimental results for 433 MHz and 2.4 GHz frequency bands. The results show its accuracy for most of the communications scenarios. © 2014 IEEE.


Tavares J.S.,INESC TEC | Pessoa L.M.,INESC TEC | Salgado H.M.,INESC TEC | Salgado H.M.,University of Porto
International Conference on Transparent Optical Networks | Year: 2015

Spatial division multiplexing (SDM) is seen as an effective technique to overcome the present limits of fiber capacity and satisfy future bandwidth requirements, by substantially increasing optical transport capacities [1-5]. Similarly to single-mode fiber based modern telecommunication systems, the nonlinear penalties will eventually become the ultimate limiting factor in SDM systems, arising from crosstalk effects in multimode core or few mode fibers, which generate intramodal and intermodal nonlinearities. Here we explore the concept of conjugated twin waves in few mode fibers based SDM optical systems, as a means to overcome these nonlinear impairments and assess the performance of SDM systems for different PCTW configurations and coupling regimes. Our numerical simulation results show that this technique is an effective means to overcome the nonlinear impairments arising in mode division multiplexed systems, improving performance by up to 10 dB, in the strong coupling regime. © 2015 IEEE.


Adao T.,INESC TEC | Magalhaes L.,INESC TEC | Peres E.,INESC TEC
Iberian Conference on Information Systems and Technologies, CISTI | Year: 2013

Video Games may be used with different applications in mind, for entertainment, training and simulation or even as teaching tools. However, the production of contents for such games, namely game scenarios with virtual worlds composed by cities and related elements (streets, buildings, furniture and so on) may require a laborious effort by multidisciplinary teams which lead to an expensive and time consuming solution. In order to avoid the development burden, procedural modeling techniques have been created and applied to generate virtual models of buildings and cities expeditiously with high degree of detail and realism. Nevertheless, most of the existing techniques use complex sets of rules to produce models without being aware of the architectonic structures and its relationships. Thereby, in order to simplify the generation process and rule dealing we propose, in this paper, an ontology-based procedural modeling methodology which integrates an ontological structure, describing city elements and the relationships between each other, and a combined set of procedural techniques to generate roman houses. The preliminary results point to a method capable of producing roman houses expeditiously, including the interiors and the exteriors. © 2013 AISTI.


Carvalho L.,University of Porto | Campos R.,INESC TEC | Ricardo M.,University of Porto
2013 IEEE 15th International Conference on e-Health Networking, Applications and Services, Healthcom 2013 | Year: 2013

Typical sensor networks are formed by low-end, battery operated devices, which rely on low-energy communication technologies, such as Bluetooth, Zigbee and ANT+, due to their energy efficiency. On the other hand, sensor networks increasingly need to be connected to the Internet, which implies adaptations of the TCP/IP stack to fit such wireless technologies. These adaptations bring additional complexity and imply new hardware, thus deployments are cumbersome and sub-optimal. Conversely, Wi-Fi is ubiquitous, can be seamlessly integrated with TCP/IP, and is energy-efficient with the right configurations; yet, its usage is still uncommon in e-health scenarios. For these reasons, we argue that a TCP/IP over Wi-Fi approach should be followed in e-health sensor networks. We propose a novel cross-layer, context-aware network configuration mechanism, which monitors the user and networking contexts and optimizes the configuration of the TCP/IP protocol stack accordingly. Our approach enables seamless integration between e-health wireless sensor networks and the TCP/IP backbone, while improving energy efficiency and reliability. © 2013 IEEE.


Pereira M.R.,INESC TEC | Santos H.M.,INESC TEC | Pessoa L.M.,INESC TEC | Salgado H.M.,INESC TEC
OCEANS 2016 - Shanghai | Year: 2016

The use of high efficiency resonant coupling wireless power systems for subsea operations is here considered for the charging of autonomous underwater vehicles. In this paper, two architectures based on two different inductors are analysed for their potential as resonant wireless power couplers. Both systems were designed and optimised through electromagnetic 3D simulations, upon which two prototypes were constructed and measured. Efficiencies as high as 75% for distances up to 5 cm were achieved on experimental testing. © 2016 IEEE.


Almeida R.,INESC TEC | Cruz N.,INESC TEC | Matos A.,INESC TEC
OCEANS 2016 - Shanghai | Year: 2016

This paper presents a new generation of man portable acoustic navigation buoys. The aim of these buoys is to facilitate the deployment of an underwater acoustic positioning system for the operation of Autonomous Underwater Vehicles. Each buoy includes only the vital modules required for the most typical schemes of underwater acoustic navigation, packed in a small but dynamically stable platform for one day long operations in coastal waters. We will present an overview of the systems hardware and electronics, and also the key features of the deployment and operation of the beacons. © 2016 IEEE.

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