Search results for: I. Godinho

Authors: L. Godinho, N. Teixeira

Abstract:

Nowadays, massification of Internet access represents one of the major challenges to the traditional powers of the State, among which the power to control its external image. The virtual world has also sparked the interest of social sciences which consider it a new field of study, an immense open text where sense is expressed. In this paper, that immense text has been accessed to so as to understand the perception Internet users from all over the world have of Portugal. Ours is a quantitative and qualitative approach, as we have resorted to buzz, thematic and category analysis. The results confirm the predominance of sea stereotype in others' vision of the Portuguese people, and evidence that national image has adapted to network communication through processes of individuation and paganization.

Keywords: national image, internet, self-communication, perception

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Authors: Theodore Grosch, Felipe Koji Godinho Hoshino

Abstract:

In wireless communications, 3GPP LTE is one of the solutions to meet the greater transmission data rate demand. One issue inherent to this technology is the PAPR (Peak-to-Average Power Ratio) of OFDM (Orthogonal Frequency Division Multiplexing) modulation. This high PAPR affects the efficiency of power amplifiers. One approach to mitigate this effect is the Crest Factor Reduction (CFR) technique. In this work, we simulate the impact of Hard Limited Clipping Crest Factor Reduction technique on BER (Bit Error Rate) in OFDM based Systems. In general, the results showed that CFR has more effects on higher digital modulation schemes, as expected. More importantly, we show the worst-case degradation due to CFR on QPSK, 16QAM, and 64QAM signals in a linear system. For example, hard clipping of 9 dB results in a 2 dB increase in signal to noise energy at a 1% BER for 64-QAM modulation.

Keywords: bit error rate, crest factor reduction, OFDM, physical layer simulation

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Authors: E. Batista, R. Mendes, A. Furtado, M. C. Ferreira, I. Godinho, J. A. Sousa, M. Alvares, R. Martins

Abstract:

Syringe pumps are commonly used for drug delivery in hospitals and clinical environments. These instruments are critical in neonatology and oncology, where any variation in the flow rate and drug dosing quantity can lead to severe incidents and even death of the patient. Therefore it is very important to determine the accuracy and precision of these devices using the suitable calibration methods. The Volume Laboratory of the Portuguese Institute for Quality (LVC/IPQ) uses two different methods to calibrate syringe pumps from 16 nL/min up to 20 mL/min. The Interferometric method uses an interferometer to monitor the distance travelled by a pusher block of the syringe pump in order to determine the flow rate. Therefore, knowing the internal diameter of the syringe with very high precision, the travelled distance, and the time needed for that travelled distance, it was possible to calculate the flow rate of the fluid inside the syringe and its uncertainty. As an alternative to the gravimetric and the interferometric method, a methodology based on the application of optical technology was also developed to measure flow rates. Mainly this method relies on measuring the increase of volume of a drop over time. The objective of this work is to compare the results of the calibration of two syringe pumps using the different methodologies described above. The obtained results were consistent for the three methods used. The uncertainties values were very similar for all the three methods, being higher for the optical drop method due to setup limitations.

Keywords: calibration, flow, interferometry, syringe pump, uncertainty

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Authors: Francesco Valerio, Sérgio Godinho, Gonçalo Ferraz, Ricardo Pita, João Gameiro, Bruno Silva, Ana Teresa Marques, João Paulo Silva

Abstract:

Remote sensing, particularly Earth Observation Satellites (EOS), provides a cost-effective solution for monitoring water resources over large spatial and temporal scales, making it valuable for systematic conservation planning targeting freshwater ecosystems. Remote sensing research only recently started to infer biophysical characteristics of small water bodies over large areas, with the most advanced techniques involving data-fusion approaches (e.g., Sentinel-1&2), ensuring Multispectral and SAR information at high spatiotemporal resolution. Considering this, an original EOS-based framework within Google Earth Engine (GEE) is presented to allow high-quality and high-frequency Sentinel-1&2 data preparation devoted to detect and monitor water surface within small water bodies. This research specifically focuses on an overlooked aspect regarding the understanding of ecohydrological processes for complex and neglected small water bodies such as ponds, as well as their seasonality in water-stressed regions. To address this gap, Sentinel-1&2-based local surface water (SLSW) models were employed, leveraging Random Forests for time series forecasting at a 15-days frequency (10 m resolution), to infer water surface occurrence and extent. The present study interested 3300 small water bodies (Mdn≈0.031 ha) in three distinct semiarid regions in SW Iberia encompassing Special Protection Areas for conservation, subjected to Mediterranean climates characterized by strong seasonality and bioclimatic changes. The SLSW models were constructed for the period from January 1, 2020, to December 31, 2021, and the results were compared with existing Landsat-based global water (LGSW) models, and separately with validation data. The SLSW models demonstrated that Multispectral and SAR-derived variables were key for water surface detection and monitoring. Considering such small-sized water bodies, classification accuracy was satisfactory in detecting surface water occurrence (μ≈72%), surpassing LGSW in completeness and capturing reconstructed seasonality patterns within and across years. The relationship between SLSW and LGSW was stronger during wet periods (R2=0.38) compared to dry periods (R2=0.05). Moreover, the SLSW models exhibited better alignment with validation data (R2=0.66) compared to LGSW (R2=0.24). This highlights the efficacy of the proposed SLSW approach in delineating dynamic surface water characteristics over extensive areas, capturing very small-sized water bodies, thereby facilitating uninterrupted high spatiotemporal detail in surface water time series data. The present research sheds light on how reconstructing archives of surface water occurrence and extent for small-sized water bodies, such as permanent and temporary ponds, which have been largely neglected despite their ecological significance. This study also contributes to the understanding of how inland freshwater resources support ecological systems and promote human development. The socio-ecological applications of this research can aid in identifying surface water anomalies and contribute to enhancing governance for sustainable water supply, a critical priority in climate change hotspots. Therefore, it is highlighted the potential of the SLSW approach in planning and supporting various activities essential for rural development and biodiversity conservation. This is especially important in areas subjected to agricultural intensification, water constraints, and given the susceptibility of water resources to climate change.

Keywords: multispectral instrument, synthetic aperture radar, surface water occurrence, surface water extent, small water bodies, google earth engine

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