2015
Authors
Rocco Giraldi, MTMR; Fernandes, CS; Ferreira, MS; de Sousa, MJ; Jorge, P; Costa, JCWA; Santos, JL; Frazao, O;
Publication
MICROWAVE AND OPTICAL TECHNOLOGY LETTERS
Abstract
In this work, it is proposed a technique to implement an intensity sensor based on the generation of a double-reflecting (ghost) signal in optical time domain reflectometry (OTDR). The intensity sensor is supported by a singlemode-multimode-singlemode (SMS) fiber structure combined with a fiber loop mirror (FLM). The results of the displacement sensitivity show linear behavior for both the first-reflecting and double-reflecting signals with linear slopes of approximately -4.5 dB/mm and -6 dB/mm, respectively. The displacement resolution achieved is approximate to 0.28 mm. It is also found that the system is able to read periodic displacement variations in the millisecond time scale applied to the sensing head. (c) 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:1312-1315, 2015
2015
Authors
Lindgren, P; Eriksson, J; Lindner, M; Lindner, A; Pereira, D; Pinho, LM;
Publication
Proceeding - 2015 IEEE International Conference on Industrial Informatics, INDIN 2015
Abstract
The IEC 61499 standard provides means to specify distributed control systems in terms of function blocks. The execution model is event driven (asynchronous), where triggering events may be associated with data (and seen as a message). In this paper we propose a low complexity implementation technique allowing to assess end-to-end response time of event chains spanning over a set of networked devices. In this paper we develop a method to provide safe end-to-end response time taking both intra- and inter-device delivery delays into account. As a use case we study the implementation onto (single-core) ARM-cortex based devices communicating over a switched Ethernet network. For the analysis we define a generic switch model and an experimental setup allowing us to study the impact of network topology as well as 802.1Q quality of service in a mixed critical setting. Our results indicate that safe sub millisecond end-to-end response times can be obtained using the proposed approach. © 2015 IEEE.
2015
Authors
Pereira, I; Madureira, A;
Publication
2015 10TH IBERIAN CONFERENCE ON INFORMATION SYSTEMS AND TECHNOLOGIES (CISTI)
Abstract
Metaheuristics are very useful to achieve good solutions in reasonable execution times. Sometimes they even obtain optimal solutions. However, to achieve near-optimal solutions, the appropriate tuning of parameters is required. This paper presents a Racing based learning module proposal for an autonomous parameter tuning of Metaheuristics. After a literature review on Metaheuristics parameter tuning and Racing approaches, the learning module is presented. A computational study for the resolution of the Scheduling problem is also presented. Comparing the preliminary obtained results with previous published results allow to conclude about the effectiveness and efficiency of this proposal.
2015
Authors
dos Santos, PL; Ramos, JA; Azevedo Perdicoulis, TP; de Carvallio, JLM;
Publication
2015 AMERICAN CONTROL CONFERENCE (ACC)
Abstract
In this article, the problem of deriving a physical model of a mechanical structure from an arbitrary state-space realization is addressed. As an alternative to finite element formulations, the physical parameters of a model may be directly obtained from identified parametric models. However, these methods are limited by the number of available sensors and often lead to poor predictive models. Additionally, the most efficient identification algorithms retrieve models where the physical parameters are hidden. This last difficulty is known in the literature as the inverse vibration problem. In this work, an approach to the inverse vibration problem is proposed. It is based on a similarity transformation and the requirement that every degree of freedom should contain a sensor and an actuator (full instrumented system) is relaxed to a sensor or an actuator per degree of freedom, with at least one co-located pair (partially instrumented system). The physical parameters are extracted from a state-space realization of the former system. It is shown that this system has a symmetric transfer function and this symmetry is exploited to derive a state-space realization from an identified model of the partially instrumented system. A subspace continuous-time system identification algorithm previously proposed by the authors in [1] is used to estimate this model from the IO data.
2015
Authors
Ikonomovska, E; Gama, J; Dzeroski, S;
Publication
NEUROCOMPUTING
Abstract
The emergence of ubiquitous sources of streaming data has given rise to the popularity of algorithms for online machine learning. In that context, Hoeffding trees represent the state-of-the-art algorithms for online classification. Their popularity stems in large part from their ability to process large quantities of data with a speed that goes beyond the processing power of any other streaming or batch learning algorithm. As a consequence, Hoeffding trees have often been used as base models of many ensemble learning algorithms for online classification. However, despite the existence of many algorithms for online classification, ensemble learning algorithms for online regression do not exist. In particular, the field of online any-time regression analysis seems to have experienced a serious lack of attention. In this paper, we address this issue through a study and an empirical evaluation of a set of online algorithms for regression, which includes the baseline Hoeffding-based regression trees, online option trees, and an online least mean squares filter. We also design, implement and evaluate two novel ensemble learning methods for online regression: online bagging with Hoeffding-based model trees, and an online RandomForest method in which we have used a randomized version of the online model tree learning algorithm as a basic building block. Within the study presented in this paper, we evaluate the proposed algorithms along several dimensions: predictive accuracy and quality of models, time and memory requirements, bias-variance and bias-variance-covariance decomposition of the error, and responsiveness to concept drift.
2015
Authors
Ren, XL; Tavares, VG; Blanton, RD;
Publication
2015 DESIGN, AUTOMATION & TEST IN EUROPE CONFERENCE & EXHIBITION (DATE)
Abstract
IEEE 1149.1, commonly known as the joint test action group (JTAG), is the standard for the test access port and the boundary-scan architecture. The JTAG is primarily utilized at the time of the integrated circuit (IC) manufacture but also in the field, giving access to internal sub-systems of the IC, or for failure analysis and debugging. Because the JTAG needs to be left intact and operational for use, it inevitably provides a "backdoor" that can be exploited to undermine the security of the chip. Potential attackers can then use the JTAG to dump critical data or reverse engineer IP cores, for example. Since an attacker will use the JTAG differently from a legitimate user, it is possible to detect the difference using machine-learning algorithms. A JTAG protection scheme, SLIC-J, is proposed to monitor user behavior and detect illegitimate accesses to the JTAG. Specifically, JTAG access is characterized using a set of specifically-defined features, and then an on-chip classifier is used to predict whether the user is legitimate or not. To validate the effectiveness of the approach, both legitimate and illegitimate JTAG accesses are simulated using the OpenSPARC T2 benchmark. The results show that the detection accuracy is 99.2%, and the escape rate is 0.8%.
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