DSpace Collection:http://hdl.handle.net/10174/11302024-03-29T09:06:31Z2024-03-29T09:06:31ZAnomalias magnéticas, alturas do geóide e variações de temperatura na plataforma do SW de PortugalDuque, Maria Rosahttp://hdl.handle.net/10174/364452024-03-18T16:38:18Z2023-05-31T23:00:00ZTitle: Anomalias magnéticas, alturas do geóide e variações de temperatura na plataforma do SW de Portugal
Authors: Duque, Maria Rosa
Abstract: Geoid height values obtained with models EGM 84, EGM96 and EGM 2008 for the region under study present significant changes, ocurring in relatively short time intervals, which can be interpreted as density changes associated with temperature variations in the region. In the present work, studies were made with data of the geomagnetic field (average hourly values) obtained at the Magnetic Observatory of Coimbra, San Fernando and Almeria, and it was concluded that anomalies detected on February 27 of 1969 can be interpreted as being obtained by suprposition of additional magnetic fields (in relation to days 25 and 26th), initially with mainly horizontal component and later with mainly vertical component. These additional fields may be associated with ion movements with mainly vertical direction followed by mainly horizontal direction. The variation in the direction of the geomagnetic field and the associated electric field lines could lead to reorientation of dipolar molecules and temperature increase in the region, whixh may have caused opening cracks and fractures already existing in the region, facilitating the entry of large amounts of water to deep zones, with relatively high speeds and temperatures.2023-05-31T23:00:00ZDensity Variations, Thermodynamic Properties and Earthquakes in the Horseshoe BasinDuque, Maria Rosahttp://hdl.handle.net/10174/364442024-03-18T16:28:45Z2023-01-01T00:00:00ZTitle: Density Variations, Thermodynamic Properties and Earthquakes in the Horseshoe Basin
Authors: Duque, Maria Rosa
Editors: Pereira, Mário Gonzalez; Oliveira, Rui; Navarro, Patrícia; Bugalho, Lourdes
Abstract: This work considers the hypotesis of heating of materials and water in the region of Bank of Gorringe and Horseshoe Basin before the earthquake of February 28, 1969. For this purpose, data from the magnetic field obtained in Magnetic Observatories of the Iberian Peninsula were analysed, and anomalies were observed, including strong variations in magnetic declination. A simple model was used to obtain the effect of heating two different media (peridotite and gabbro) in physical contact, with different thermal and mechanical properties. The results include compression of peridotite by gabbro and shear stresses in the contact of the two materials2023-01-01T00:00:00ZAddressing the effect of hole design on the performance of perforated platesMiguel, A. F.http://hdl.handle.net/10174/353802023-08-03T10:26:22Z2023-06-30T23:00:00ZTitle: Addressing the effect of hole design on the performance of perforated plates
Authors: Miguel, A. F.
Abstract: Perforated plates have been used in a variety of applications for many years. Shading panels [1], sound absorption [2], separators and filters [3], heat exchangers [4], and applications requiring homogeneous flows [5] are just a few examples. Homogeneous flows are critical for climatization of enclosures and cooling purposes such as gas turbine blades. This ensures that the fluid is distributed evenly, and in case of blades it protects the blade surface from hot gases.
This study is devoted to understanding fluid flow in perforated plates. Their performance and dependability are critical factors that are object of study in order to build, develop, evaluate, and manage perforated plates to maximize their functionality. The hole geometry has a direct impact on the transport properties of these plates. Understanding how the geometry of holes affects fluid flow is thus critical for designing increasingly efficient systems. As a result, we investigate the effects of hole design on fluid flow using a Computational Flow Dynamics approach. Plates with round holes and plates with square holes with porosities ranging from 0.2 to 0.8 are investigated. The numerical investigation is carried out for Reynolds numbers ranging from 102 to 104. Among the outcomes are equations for loss factors for each design.2023-06-30T23:00:00ZEvaluation of an All Sky Imager Based Nowcasting System for Distinct Conditions and Five SitesNouri, B.Wilbert, S.Blum, N.Kuhn, P.Schmidt, T.Yasser, Z.Schmidt, T.Zarzalejo, L.F.Lopes, F.M.Silva, Hugo G.Schroedter-Homscheidt, M.Kazantzidis, A.Raeder, C.Blanc, P.Pitz-Paal, R.http://hdl.handle.net/10174/334882023-01-16T16:29:44Z2020-01-01T00:00:00ZTitle: Evaluation of an All Sky Imager Based Nowcasting System for Distinct Conditions and Five Sites
Authors: Nouri, B.; Wilbert, S.; Blum, N.; Kuhn, P.; Schmidt, T.; Yasser, Z.; Schmidt, T.; Zarzalejo, L.F.; Lopes, F.M.; Silva, Hugo G.; Schroedter-Homscheidt, M.; Kazantzidis, A.; Raeder, C.; Blanc, P.; Pitz-Paal, R.
Abstract: All sky imager (ASI) based nowcasting system can provide spatially and temporally highly resolved solar
irradiance information for the next minutes ahead. Nowcasts, which capture the intra-hour variability of the incoming
downward shortwave solar irradiance, have the potential to optimize the operation of solar power plants as well as
electrical grids. Such automatized optimizations require a deep understanding of the accuracy in the nowcasting system at
any given moment. State of the art validation procedures of ASI based nowcasting systems use scalar error metrics
without regards to the actual weather conditions. Yet, the performance of nowcasting systems varies strongly with the
prevailing weather conditions. Deviations increase for more complex and variable conditions, for which it is more
challenging to detect and model the clouds in the sky. Thus, depending on the used data set such validation results may
not be meaningful to describe the expected accuracy in realistic and individual optimization situations. A novel validation
procedure is presented in this work, which discretizes the validation data set in distinct temporal DNI variability classes.
Individual error metrics are determined as function of the lead time and DNI variability class. This approach is applied
for a two ASI based nowcasting system as operated on five distinct sites distributed in Spain, Portugal and Germany,
over a combined period of more than 4.5 years. The obtained validation results emphasize that the novel classification
method enables a comparison in nowcast performance between the sites despite of distinct local meteorological
conditions. The presented method allows the estimation of the overall accuracy of nowcasting systems at a new site if
DNI data in 1 min resolution are available.2020-01-01T00:00:00Z