1,314 research outputs found
O Pulsar da Actividade Física no Ensino Pré-Escolar
p. 63-69Com este texto pretendemos exorcisar determinadas
concepções e apresentar a nossa visão de que o sucesso,
no desporto pré-escolar e na Educação Física na escola,
passa por um entendimento mais amplo e abrangente
que o mero espaço confinado ao ginásio ou à intervenção
do agente educativo. De facto, o desenvolvimento
motor da criança é influenciado por uma complexidade
de contextos, com especial relevo para as actividades
informais de rua, no recreio escolar, em actividades institucionalizadas
de tempos livres e através do jogo.
Quando uma criança em idade pré-escolar apresenta
dificuldades de escrita, leitura, desenho, etc, algo do
movimento não está suficientemente coordenado comparativamente
com os padrões normalmente aceites. Na
incapacidade, normalmente detectada, e após uma avaliação
feita pelo Educador, detecta-se uma insuficiência
de movimentos coordenados, mediante umas acções e
reações musculares inadaptadas, anti-funcionais, anti -
-económicas e espacialmente inadequadas dos impulsos,
podendo traduzir-se e transformar-se num futuro próximo
em problemas de comportamento, baixa auto -
-estima, insegurança e fragilidade psicológica.
A actividade física na idade Pré-Escolar é, por todos os
agentes da Educação, aceite como uma das actividades
com maior relevância para o desenvolvimento integral
da criança, porque promove o seu desenvolvimento e lhe
proporciona enriquecedoras situações motrizes, potenciando
a aquisição de valores educativos que contribuirão
para um projecto de vida com saúde e socialmente
saudável
Design of Analog-to-Digital Converters with Embedded Mixing for Ultra-Low-Power Radio Receivers
In the field of radio receivers, down-conversion methods usually rely on one (or more)
explicit mixing stage(s) before the analog-to-digital converter (ADC). These stages not
only contribute to the overall power consumption but also have an impact on area and can
compromise the receiver’s performance in terms of noise and linearity. On the other hand,
most ADCs require some sort of reference signal in order to properly digitize an analog
input signal. The implementation of this reference signal usually relies on bandgap
circuits and reference buffers to generate a constant, stable, dc signal. Disregarding this
conventional approach, the work developed in this thesis aims to explore the viability
behind the usage of a variable reference signal. Moreover, it demonstrates that not only
can an input signal be properly digitized, but also shifted up and down in frequency,
effectively embedding the mixing operation in an ADC. As a result, ADCs in receiver
chains can perform double-duty as both a quantizer and a mixing stage. The lesser known
charge-sharing (CS) topology, within the successive approximation register (SAR) ADCs,
is used for a practical implementation, due to its feature of “pre-charging” the reference
signal prior to the conversion. Simulation results from an 8-bit CS-SAR ADC designed in
a 0.13 μm CMOS technology validate the proposed technique
Implementation of a sigma delta modulator for a class D audio power amplifier
Dissertação para obtenção do Grau de Mestre em
Engenharia Electrotécnica e de Computadore
Actividade neotectónica na região do Algarve, S. de Portugal
O enquadramento tectónico da região do Algarve, situada junto à margem continental oeste-ibérica, em transição para uma
fronteira de placas convergente, e próximo da zona de fractura Açores-Gibraltar, explica as actividades tectónica e sísmica
significativas que se verificam na região. A actividade tectónica regional plio-quaternária é evidenciada por deslocamentos verticais
da crosta e por numerosas estruturas activas identificadas às escalas macro e mesoscópica, representadas por alguns
dobramentos e por abundantes fracturas (falhas e diaclases). Diversas estruturas que afectam os sedimentos plio-quaternários
foram interpretadas como paleossismitos. Algumas destas estruturas resultam provavelmente de vibrações relacionadas com a
ocorrência de sismos fortes distantes, mas a proximidade de muitos dos sismitos a falhas activas conhecidas sugere a sua relação
com eventos de magnitude moderada a elevada (M >= 5,5) gerados por essas falhas. A ocorrência desses eventos é compatível
com a sismicidade regional conhecida, embora alguns dos paleossismitos indiquem um limiar superior para a magnitude dos sismos
locais
A baseband wireless spectrum hypervisor for multiplexing concurrent OFDM signals
The next generation of wireless and mobile networks will have to handle a significant increase in traffic load compared to the current ones. This situation calls for novel ways to increase the spectral efficiency. Therefore, in this paper, we propose a wireless spectrum hypervisor architecture that abstracts a radio frequency (RF) front-end into a configurable number of virtual RF front ends. The proposed architecture has the ability to enable flexible spectrum access in existing wireless and mobile networks, which is a challenging task due to the limited spectrum programmability, i.e., the capability a system has to change the spectral properties of a given signal to fit an arbitrary frequency allocation. The proposed architecture is a non-intrusive and highly optimized wireless hypervisor that multiplexes the signals of several different and concurrent multi-carrier-based radio access technologies with numerologies that are multiple integers of one another, which are also referred in our work as radio access technologies with correlated numerology. For example, the proposed architecture can multiplex the signals of several Wi-Fi access points, several LTE base stations, several WiMAX base stations, etc. As it able to multiplex the signals of radio access technologies with correlated numerology, it can, for instance, multiplex the signals of LTE, 5G-NR and NB-IoT base stations. It abstracts a radio frequency front-end into a configurable number of virtual RF front ends, making it possible for such different technologies to share the same RF front-end and consequently reduce the costs and increasing the spectral efficiency by employing densification, once several networks share the same infrastructure or by dynamically accessing free chunks of spectrum. Therefore, the main goal of the proposed approach is to improve spectral efficiency by efficiently using vacant gaps in congested spectrum bandwidths or adopting network densification through infrastructure sharing. We demonstrate mathematically how our proposed approach works and present several simulation results proving its functionality and efficiency. Additionally, we designed and implemented an open-source and free proof of concept prototype of the proposed architecture, which can be used by researchers and developers to run experiments or extend the concept to other applications. We present several experimental results used to validate the proposed prototype. We demonstrate that the prototype can easily handle up to 12 concurrent physical layers
Extensional orogenic collapse captured by strike-slip tectonics:
The late Paleozoic collision between Gondwana and Laurussia resulted in the polyphase deformation and
magmatism that characterizes the Iberian Massif of the Variscan orogen. In the Central Iberian Zone, initial con-
tinental thickening (D1; folding and thrusting) was followed by extensional orogenic collapse (D2) responsible
for the exhumation of high-grade rocks coeval to the emplacement of granitoids.
This study presents a tectonometamorphic analysis of the Trancoso-Pinhel region (Central Iberian Zone) to ex-
plain the processes in place during the transition froman extension-dominated state (D2) to a compression-dom-
inated one (D3).Wereveal the existence of low-dipping D2 extensional structures later affected by several pulses
of subhorizontal shortening, each of them typified by upright folds and strike-slip shearing (D3, D4 and D5, as
identified by superimposition of structures). The D2 Pinhel extensional shear zone separates a low-grade domain
from an underlying high-grade domain, and it contributed to the thermal reequilibration of the orogen by facil-
itating heat advection from lower parts of the crust, crustal thinning, decompression melting, and magma intru-
sion. Progressive lessening of the gravitational disequilibrium carried out by this D2 shear zone led to a switch
from subhorizontal extension to compression and the eventual cessation and capture of the Pinhel shear zone
by strike-slip tectonics during renewed crustal shortening. High-grade domains of the Pinhel shear zone were
folded together with low-grade domains to define the current upright folded structure of the Trancoso-Pinhel re-
gion, the D3 Tamames-Marofa-Sátão synform. Newdating of syn-orogenic granitoids (SHRIMP U\\Pb zircon dat-
ing) intruding the Pinhel shear zone, together with the already published ages of early extensional fabrics
constrain the functioning of this shear zone to ca. 331–311 Ma, with maximum tectonomagmatic activity at ca.
321–317 Ma. The capture and apparent cessation of movement of the Pinhel shear zone occurred at ca. 317–
311 Ma
Strike-slip shear zones of the Iberian Massif: Are they coeval?
Strike-slip shear zones of the Variscan orogen are used to derive the evolution of paleostrain and discuss the kinematics of the waning stages
of the Gondwana-Laurussia collision during the amalgamation of Pangea. In the Iberian Massif, the recognition of three late Carboniferous
deformation events related to strike-slip tectonics (D3, D4, D5) in the Trancoso-Pinhel region (Portugal) reveals that late orogenic transcurrent
deformation was episodic and occurred in a short period of time (<15 m.y.). Early stages of strike-slip deformation included dextral and sinistral
shear zones and orogen-parallel upright folds (D3; ca. 311 Ma). These structures followed the development of extensional shear zones (D2) during
the tectonothermal reequilibration of the orogen. D3 structures were deflected and folded by the sinistral D4 Juzbado-Penalva do Castelo
shear zone, dated as ca. 309–305 Ma by SHRIMP (sensitive high-resolution ion microprobe) U-Pb zircon dating of synkinematic granitoids.
D3 and D4 structures were folded under east-west compression (D5) influenced by the strike-slip movement of the dextral Porto-Tomar shear
zone. Variscan movement along the Porto-Tomar shear zone started ca. 304 Ma (onset of the Buçaco basin and syn-D5 granites), but ceased
before ca. 295 Ma (age of the final closure of the Ibero-Armorican arc and crosscutting granites). The contrasting geometry, kinematics, and
timing of these strike-slip shear zones are explained by deformation partitioning upon a rheologically inhomogeneous crust with structural
and tectonothermal anisotropies generated during previous deformation. The convergence vector between Gondwana and Laurussia during
D3–D5 remained the same, and was equivalent to the vector that explains the previous tectonic record (D2) in central and northwestern Iberia
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