Electric properties of granitic rocks

The objective of this work is to clarify the role of water content on the charge trans- port mechanisms of different granitic rocks. The mineralogical content of the rocks will also be taken into account. From the electrical point of view these materials are rather insulating porous media where charge injection creates different phenomena like build-up charges, space charge limited currents, surface effects and other behav- iors that resemble much a variety of oxides, like AlO

Magnetic and spin waves studies in amorphous Gd 0.7 Y 0.3

In this paper, magnetic properties of amorphous Gd0.7 Y0.3 alloys have been studied using a linear dependence on H-1/2 of the saturation magnetization M(H); this dependence has been proved to be necessary for an adequate interpretation of magnetic behaviour of ferromagnetic amorphous compounds. Indeed, in a previous work, assuming a linear dependence on H-1 of M(H), magnetic parameters (magnetic moment, µGd , of Gd, mean exchange integral (J)) relevant to Gd0.7 Y0.3 have been undervalued. In the present work, these parameters, in addition to the stiffness constant, have been improved.In this paper, magnetic properties of amorphous Gd0.7 Y0.3 alloys have been studied using a linear dependence on H-1/2 of the saturation magnetization M(H); this dependence has been proved to be necessary for an adequate interpretation of magnetic behaviour of ferromagnetic amorphous compounds. Indeed, in a previous work, assuming a linear dependence on H-1 of M(H), magnetic parameters (magnetic moment, µGd , of Gd, mean exchange integral (J)) relevant to Gd0.7 Y0.3 have been undervalued. In the present work, these parameters, in addition to the stiffness constant, have been improved

Seismo-electromagnetic phenomena in the western part of the Eurasia-Nubia plate boundary

This paper presents a future research plan that aims to monitor Seismo-electromagnetic (SEM) phenomena in the western part of the Eurasia-Nubia plate boundary (WENP). This region has a significant tectonic activity [1] combined with relatively low electromagnetic noise levels and for that reason presents the possibility to perform high quality SEM measurements. Further, it is known that low-frequency [ultra (ULF), very (VLF), and low-frequencies (LF)] electromag- netic (EM) waves produce more convincing earthquake precursors (compared to higher frequencies) because of less contamination, large skin depth, and low attenuation [2]. Thus, two SEM effects will be considered: ULF electromagnetic field emissions [3], and VLF/LF radio broadcastings [4]. With respect to the ULF measurements, as a start, three ULF sensors are planned to be installed in the South of Iberian Peninsula supported by the existing networks of seismic research stations. Subsequent devel- opment of this initial plan could result in the implementation of a lager ULF monitoring network not only in the Iberian Peninsula, but also in the rest of Europe. Possible integration in the SEGMA array is now under consideration. Another perspective is to use a portable station to track seismic events. Regarding the VLF/LF radio broadcastings, a receiver is planned to be mounted in University of Évora. Radio signals from up to 10 transmitters (in these bands) of interest to study the seismic activity in the WENP region will be monitored. Actually, the radio path from the transmitter to the receiver should cross the epicentral area, therefore two possible transmitters are the ones installed in Monaco (France) and Sicily (Italy). Furthermore, the system will integrate the INFREP network and in this context it will not be restricted to WENP region. With the development of these research plans we aim to collect novel SEM data emerging from the seis- mic activity in the WENP region. We expect to address the time variations of EM properties of the crust/plate in relation with the strain field, and in space in relation with composition and temperature and stress fields. Further, the interplay between atmospheric (and solar) perturbations with crust perturbations will be monitored, to observe geomagnetic perturbations at different locations. Our study will be focused in the analyses of low magnitude earthquakes with M =< 4, these events are frequent in the WENP region, but have been almost completely disregarded in literature [5,6]. [1] J. Borges, A. J. S. Fitas, M. Bezzeghoud, and P. Teves-Costa, Tectonophysics 337, 373 (2001). [2] V. Chauhan, O.P. Singh, V. Kushwah, V. Singh, B. Singh, Journal of Geodynamics 48, 68 (2009). [3] L. Telesca, V. Lapenna, M. Macchiato, and K. Hattori, Earth and Planet. Science Lett. 268, 219 (2008)

Analysis of a Non-Iterative Algorithm for the Amplitude and Phase Difference Estimation of Two Acquired Sinewaves

In this paper, a non-iterative algorithm for amplitude and phase difference estimation of two acquired sinewaves is presented and analyzed. The method is based on the least-squares fitting of ellipses where the common signal frequency is eliminated from the algorithm

A New Approach of Total Least Square Algorithm for Parameter Extraction of a Photovoltaic Panel: A Comparison Study

The degradation of the photovoltaic panels due to their long outdoor exposure leads to a variation in their internal parameters. The function describing the I-V characteristic of the photovoltaic cell is known to be non-linear and implicit, with five unknown parameters. To identify these photovoltaic parameters, the cost function used for optimization is the Total Least Square function (TLS), defined as a sum of quadratic terms representing the quantification of the errors between a mathematical model and a measured set of experimental data, which is usually accompanied by measurement uncertainties (measuring current and voltage). However, the studies that have been done so far to extract the photovoltaic parameters work with the Ordinary Least Square (OLS) function defined as the sum of quadratic terms representing the quantification of the errors between a mathematical model and a measured set of experimental data of one variable (current only), because it is facile to apply, especially in the case of nonlinear models. Nether less, taking into account both differences in measurement uncertainties accompanying both variables will help to achieve more efficient optimization and more precise results. This work presents a new iterative, simple to implement algorithm that can calculate the value of the Total Least Square function at each step of the optimization process. The results are then compared with the ones obtained by applying the OLS function

A New Prototype for Automatic Identification of Stone Block Internal Structure

: Nowadays, the inner shape and economic viability of a stone block is dependent on the skill and experience of the “expert” that makes predictions based on external observations. This actual procedure is an extremely high empirical method, and when it fails, substantial work, time, and money is wasted. At present, researchers are committed to developing models to predict the stone block internal structure based on non‐destructive tests. Ultrasonic tomography and electrical resistivity tomography are the tests that best fit these objectives. Trying to improve the existing procedures for collecting stone information and data exporting, a novel approach to perform both tomographies is proposed in this paper. This novel approach presents sound advantages regarding the current manual procedure: namely, (i) high accuracy due to a new automatic positioning system; (ii) no need for highly skilled operators to process measurements; (iii) measurements are much easier to derive, and results are quickly delivered. A comparison between the new automatic process and the current manual procedure shows that the manual procedure has a very low accuracy when compared to the new developed automatic system. The automatic measurements show extremely significant time savings, which is a relevant issue for the future competitiveness of the stone sector

Chaotic behaviour of seismic mechanisms: observation and models

Today, it is impractical work modelling the dynamics of failure, given the high complexity of the systems involved. As soon, it is important to identify models, as simples as possible, with qualitatively similar to the failures. The first model introducing is it the mechanical block-spring model, given by Burrigde-Knopoff [1]. In this work the subject was treated by experimental means. For that purpose it was developed and designed a mechanical system similar it that used in the numerical modulations, the so called earthquake machine (shown in Figure 1). We have equipped the springs of the machine with a set of force sensors connected to a data acquisition system (DAQ), linked in turn to a computer. The data recorded in the mechanical prototype consists of temporal series of tensions measured by the sensors that correspond to the sequence of tension accumulation and drop taking place in the springs. Data processing followed two distinct methodologies. The first treated the data according to the techniques used in seismology with field measurements. In the second methodology, we tried to use the series recorded in the context of chaos theories to investigate the behaviour of prototype

DIFFERENT OPTIMIZATION TECHNIQUES OF WIRELESS MESH NETWORKS FOR PHOTOVOLTAIC APPLICATION

With the advancement of technology the internet technology is evolving and it is facing new challenges to the betterment of the quality of service. Mesh Networks are an important topology where the fixed wireless network is established to provide network services. Wireless Mesh Network (WMN) is getting acknowledgment for advanced networking purposes. Mainly performance of this kind of network is dependent on the assignment of the channel and the scheme of routing. The photovoltaic network is a new concept that is combined with the Internet of Things to take advantage of the panel’s monitoring system. Large-scale WMN, combined with a photovoltaic system requires optimization techniques to improve the quality and efficiency of service. Covering and sharing information between all nodes in the network is crucial for PV and the Internet of Things (IoT). Power consumption is a significant part of low-power WMN and IoT. This article provides different optimization techniques and analyzes different algorithms to understand the better solution for a wireless mesh network in the ground of photovoltaic networking

Supressão do Campo Eléctrico Atmosférico aquando do sismo de Sousel, M = 4.1

In recent years different phenomena associated with seismic events have been referred in the literature. These include: unusual ultra-low-frequency electromagnetic emissions; anomalies in radio transmissions; variation of the ionosphere total electron content; and anomalous levels of different geochemical elements (in particular radon) in the earthquake preparation zone. Recent works shown the possibility of enhanced air ionization, with consequent atmospheric electricity perturbations, in the preparatory stage of seismic events. They relate possible atmospheric electrical field anomalies during the earthquake preparation with surface air ionization through radon emanations. In fact, this work presents the observation of a significant suppression of the vertical component of the atmospheric electrical field that occurred in Évora (Portugal) soon before the M = 4.1 Sousel earthquake of 27 March 2010. The observation is reported, followed by the analysis and interpretation. Preliminary conclusions and plans for future works are drawn