Validation of the Lower Tagus Valley velocity and structural model using ambient noise broadband measurements

Along his history the Lower Tagus Valley (LTV) region was shaken by several earthquakes, some of them were produced in large ruptures of offshore structures located southwest of the Portuguese coastline, among these we the Lisbon earthquake of 1 November 1755; other moderates earthquakes were produced by local sources such as the 1344, 1531 and the 1909 Benavente earthquake. In order to promote an improved assessment of the seismic hazard in this region, we propose the introduction of realistic methods on the prediction of ground motion produced by moderate to large earthquakes in LTV. This process involves the establishment of a structural 3D model based on all the available geophysical and geotechnical data on the area (seismic, gravimetric, deep wells and geological outcrops) and the determination of wave propagation from a finite difference method: by applying the E3D program [1,2]. To confirm this model we use broadband ambient noise measurements collected in two profiles with azimuth perpendicular to the basin axis and we applied the horizontal to vertical (H/V) spectral ratio method [3] to the recordings in order to estimate the amplification of the basin. The H/V curves obtained reveals the existence of two low frequency peaks centered on 0.2 a 1 Hz frequencies[4]. These peaks are strongly related with the thickness of Cenozoic and alluvial sediments. By inversion of the H/V curve, we obtain a more detailed velocity model for the region where the profile were determined, which is in good agreement with borehole data and other results obtained with magnetic and seismic reflection methods

Prefilter bandwidth effects in data symbol phase synchronizers of open loop

This work studies the effects of the prefilter bandwidth on the open loop symbol synchronizers. We consider three different prefilter bandwidth, namely, B1=¥ ( infinite), B2=2.tx and B3=1.tx, where tx is the transmission rate. We consider also four open loop symbol synchronizers, namely, the tank (tank), the SAW (SAW), the monostable (mon), and the astable (ast). The objective is to study the prefilter bandwidth with the four open loop symbol synchronizers and to evaluate their output jitter UIRMS (Unit Interval Root Mean Square) versus input SNR (Signal to Noise Ratio)

Prefilter bandwidth effects in sequential symbol synchronizers based on clock sampling by positive transitions

This work studies the effects of the prefilter bandwidth in the sequential symbol synchronizers based on clock sampling by positive transitions. The prefilter bandwidth B is switched between three values, namely B1=∞, B2=2. tx and B3=1. tx, where tx is the bit rate. The synchronizer has two variants, one discrete and other continuous. Each variant has two versions, one manual and other automatic. The objective is to study the prefilter bandwidth with the four synchronizers and to evaluate their output jitter UIRMS (Unit Interval Root Mean Square) versus input SNR (Signal to Noise Ratio)

Sequential symbol synchronizers based on clock sampling by positive transitions

This work presents a sequential symbol synchronizer, that was discovered by us, and its functioning principle is based on the clock sampling by the input positive data transitions. This synchronizer has two topologies, namely the discrete and the continuous. Also, each topology has two versions which are the manual and the automatic. These synchronizers are very interesting, because the previous adjust of the manual version isn’t critical. The objective is to study the four synchronizers and to evaluate their output jitter UIRMS (Unit Interval Root Mean Square) versus input SNR (Signal to Noise Ratio)

Effects of the previous pulse shift and filter on the symbol synchronizer PLL

We will study the effects of the shift of the previous pulse temporal position (between P1 and P2) on the symbol synchronizers jitter behavior. Each pulse temporal position (P1 and P2), with the same previous filter, forms a group with four different carrier PLL (Phase Lock Loop) namely the analog, hybrid, combinational and sequential. The main objective is to study the synchronizers output jitter UIRMS (Unit Interval Root Mean Squared) as function of the input SNR (Signal to Noise Ratio)

Sequential symbol synchronizers based on pulse comparison operating by positive transitions at quarter rate

This work presents the sequential symbol synchronizer based on pulse comparison by positive transitions at quarter rate (txp/4). Their performance is compared with a reference synchronizer by both transitions at the rate (tx). For the reference and proposed synchronizer we consider two versions which are the manual (m) and the automatic (a). The objective is to study the four synchronizers and evaluate their output jitter UIRMS (Unit Interval Root Mean Square) versus input SNR (Signal Noise Ratio)

Sequential symbol synchronizers based on pulse comparation at Half Rate

This work presents a synchronizer based on pulse comparation, between variable and fixed pulses. We consider four synchronizers, divided in two variants, one variant operate at the rate and the other at half rate. Each synchronizer variant has two versions which are the manual and the automatic. The objective is to study the synchronizers and evaluate the output jitter UIRMS (Unit Interval Root Mean Square) versus the input SNR (Signal Noise Ratio)

Synchronous and asynchronous sequential symbol synchronizers

In this work, we present two synchronizer groups: the synchronous and the asynchronous. The synchronous group is based in forward logic with flip flops and the asynchronous group is based in forward logic with delay line feedback. In each group we consider two versions: the manual and the automatic. The main objective is to study the two groups, each one with two versions and to observe its jitter performance as function of the noise

Building on teachable moments: issues for teacher education

This work is supported by national funds through FCT – Fundação para a Ciência e Tecnologia, under the projects Professional Practices of Teachers of Mathematics (Grant PTDC/CPE-CED/098931/2008) and PEst-C/MAT/UI0144/2011, and by FEDER funds through COMPETESeveral authors have given attention to the notion of didactical knowledge, which is not consensual (Ponte, in press). We consider didactical knowledge as being related to aspects of teachers’ practices, “essentially oriented towards action” (Ponte, 1999, p. 61), and involving four dimensions: knowledge of the curriculum, knowledge of mathematics, knowledge of students and their learning processes, and knowledge instructional processes in the classroom (Ponte & Oliveira, 2002). The didactical knowledge has a dynamic character because the experiences teachers encounter in their practice constantly shape it (Ponte & Santos, 1998).FC

NEW SEISMIC SOURCE ZONE MODEL FOR PORTUGAL AND AZORES

The development of seismogenic source models is one of the first steps in seismic hazard assessment. In seismic hazard terminology, seismic source zones (SSZ) are polygons (or volumes) that delineate areas with homogeneous characteristics of seismicity. The importance of using knowledge on geology, seismicity and tectonics in the definition of source zones has been recognized for a long time [1]. However, the definition of SSZ tends to be subjective and controversial. Using SSZ based on broad geology, by spreading the seismicity clusters throughout the areal extent of a zone, provides a way to account for possible long-term non-stationary seismicity behavior [2,3]. This approach effectively increases seismicity rates in regions with no significant historical or instrumental seismicity, while decreasing seismicity rates in regions that display higher rates of seismicity. In contrast, the use of SSZ based on concentrations of seismicity or spatial smoothing results in stationary behavior [4]. In the FP7 Project SHARE (Seismic Hazard Harmonization in Europe), seismic hazard will be assessed with a logic tree approach that allows for three types of branches for seismicity models: a) smoothed seismicity, b) SSZ, c) SSZ and faults. In this context, a large-scale zonation model for use in the smoothed seismicity branch, and a new consensus SSZ model for Portugal and Azores have been developed. The new models were achieved with the participation of regional experts by combining and adapting existing models and incorporating new regional knowledge of the earthquake potential. The main criteria used for delineating the SSZ include distribution of seismicity, broad geological architecture, crustal characteristics (oceanic versus continental, tectonically active versus stable, etc.), historical catalogue completeness, and the characteristics of active or potentially-active faults. This model will be integrated into an Iberian model of SSZ to be used in the Project SHARE seismic hazard assessment