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Publications

2010

PS-InSAR processing methodologies in the detection of field surface deformation Study of the Granada basin (Central Betic Cordilleras, southern Spain)

Authors
Sousa, JJ; Ruiz, AM; Hanssen, RF; Bastos, L; Gil, AJ; Galindo Zaldivar, J; de Galdeano, CS;

Publication
JOURNAL OF GEODYNAMICS

Abstract
Differential SAR interferometry (DInSAR) is a very effective technique for measuring crustal deformation. However, almost all interferograms include large areas where the signals decorrelate and no measurements are possible. Persistent scatterer interferometry (PS-InSAR) overcomes the decorrelation problem by identifying resolution elements whose echo is dominated by a single scatterer in a series of interferograms. Two time series of 29 ERS-1/2 and 22 ENVISAT ASAR acquisitions of the Granada basin, located in the central sector of the Betic Cordillera (southern Spain), covering the period from 1992 to 2005, were analyzed. Rough topography of the study area associated to its moderate activity geodynamic setting, including faults and folds in an uplifting relief by the oblique Eurasian-African plate convergence, poses a challenge for the application of interferometric techniques. The expected tectonic deformation rates are in the order of similar to 1 mm/yr, which are at the feasibility limit of current InSAR techniques. In order to evaluate whether, under these conditions, InSAR techniques can still be used to monitor deformations we have applied and compared two PS-InSAR approaches: DePSI, the PS-InSAR package developed at Delft University of Technology (TU Delft) and StaMPS (Stanford Method for Persistent Scatterers) developed at Stanford University. Ground motion processes have been identified for the first time in the study area, the most significant process being a subsidence bowl located at the village of Otura. The idea behind this comparative study is to analyze which of the two PS-InSAR approaches considered might be more appropriate for the study of specific areas/environments and to attempt to evaluate the potentialities and benefits that could be derived for the integration of those methodologies.

2010

A hybrid Fabry-Perot/Michelson interferometer sensor using a dual asymmetric core microstructured fiber

Authors
Frazao, O; Silva, SF; Viegas, J; Baptista, JM; Santos, JL; Roy, P;

Publication
MEASUREMENT SCIENCE & TECHNOLOGY

Abstract
A hybrid Fabry-Perot/Michelson interferometer sensor using a dual asymmetric core microstructured fiber is demonstrated. The hybrid interferometer presents three waves. Two parallel Fabry-Perot cavities with low finesse are formed between the splice region and the end of a dual-core microstructured fiber. A Michelson configuration is obtained by the two small cores of the microstructured fiber. The spectral response of the hybrid interferometer presents two pattern fringes with different frequencies due to the respective optical path interferometers. The hybrid interferometer was characterized in strain and temperature presenting different sensitivity coefficients for each topology. Due to these characteristics, this novel sensing head is able to measure strain and temperature, simultaneously.

2010

A TDMA-based Mechanism for Real-Time Communication in IEEE 802.11e Networks

Authors
Costa, R; Portugal, P; Vasques, F; Moraes, R;

Publication
2010 IEEE CONFERENCE ON EMERGING TECHNOLOGIES AND FACTORY AUTOMATION (ETFA)

Abstract
In this paper, we propose a TDMA-based communication approach to be used upon the EDCA communication mechanism defined in the IEEE 802.11e standard. This approach allows the coexistence of realtime (RT) traffic together with uncontrolled (external) traffic sources. In the context of this paper, RT traffic means small sized packets generated in periodic intervals, which must be delivered before the end of the message stream period. The target of this paper is to highlight some limitations of the EDCA mechanism when supporting RT communication and to compare these results with those obtained with the proposed TDMA approach. We have assessed these two mechanisms considering an open communication environment, where there are RT and non-RT stations operating in the same frequency band. Furthermore, a realistic error-prone model channel was used to measure the impact of interferences against an error-free channel. We show that the proposed TDMA approach offers an almost constant access delay and it also improves the EDCA behavior in what concerns the average functional throughput and the average deadline losses.

2010

Coarse WDM networking of self-referenced fiber-optic intensity sensors with reconfigurable characteristics

Authors
Montero, DS; Vazquez, C; Baptista, JM; Santos, JL; Montalvo, J;

Publication
OPTICS EXPRESS

Abstract
A CWDM network operating in reflective configuration for multiplexing remote Radio-Frequency (RF) self-referenced fiber-optic intensity sensors is analyzed and experimentally investigated. In the described approach, the use of fiber Bragg gratings as spectral selective mirrors allows to implement delay lines in the electrical domain, achieving more compact sensor-heads and easy-reconfigurable sensing points. Two measurement parameters for the sensing heads are defined and comparatively studied in terms of design parameters, linearity, sensitivity and resolution. The proposed sensor configuration is modeled following the Z-transform formalism, which permits an easy analysis of the system frequency response. Experimental results are presented, showing the characterization of the network performance and considering the properties of sensor self-referencing as well as sensor crosstalk. (C) 2010 Optical Society of America

2010

Wind Power Forecasting in U.S. Electricity Markets

Authors
Botterud, A; Wang, J; Miranda, V; Bessa, RJ;

Publication
Electricity Journal

Abstract
Wind power forecasting is becoming an important tool in electricity markets, but the use of these forecasts in market operations and among market participants is still at an early stage. The authors discuss the current use of wind power forecasting in U.S. ISO/RTO markets, and offer recommendations for how to make efficient use of the information in state-of-the-art forecasts. © 2010 Elsevier Inc.

2010

Towards a WirelessHART module for the Ns-3 Simulator

Authors
Nobre, M; Silva, I; Guedes, LA; Portugal, P;

Publication
2010 IEEE CONFERENCE ON EMERGING TECHNOLOGIES AND FACTORY AUTOMATION (ETFA)

Abstract
This work has the objective to present the first development results of a WirelessHART module for the ns-3. Our focus is the implementation of the Physical layer in order to provide the basis for the development of the superior layers such as MAC and Application. Thus, we presente an energy consumption model, a Gilbert/Elliot error model and an analysis for the currently avaliable ns-3 propagation loss models. For further development we mainly aim for the implementation of the time slot scheduler ( Network Manager) and the development of an inter protocol simulation with mutual interference.

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