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2DOF-based current controller for single-phase grid-connected voltage source inverter applications
(Elsevier, 2023-05-02) López Alcolea, Francisco Javier; Molina Martínez, Emilio José; Parreño Torres, Alfonso; Vázquez del Real, Javier; Roncero Sánchez Elipe, Pedro Luis
This paper presents the design of a discrete-time control scheme for the current injected into the grid by a single-phase voltage source inverter (VSI). The VSI is connected to the grid by means of an LCL filter that attenuates the switching harmonics present in the output waveform of the inverter. The current control is based on a resonant regulator implemented in a Two-Degrees-Of-Freedom (2DOF) scheme that allows the location of all the poles to be defined in the closed loop of the system without the need for observers and measuring only the current injected into the grid. This control scheme, therefore, allows the attenuation of the resonance frequency of the LCL filter and requires no additional damping methods with which to mitigate the resonance phenomenon. The design parameters can be obtained using a fairly straightforward mathematical approach that involves only operations with real numbers. The simulation and experimental results obtained show that the control scheme performs correctly even considering changes in the grid inductance.
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Assessment of functional respiratory complaints and related factors in people with hypermobile Ehlers-Danlos syndrome: Cross-sectional study
(Elsevier, 2023-06-15) Reina Gutiérrez, Sara; Caty, Gilles D.; Torres Costoso, Ana Isabel; Pitance, Laurent; Manicourt, Daniel Henri; Reychler, Grégory
Background Hypermobile Ehlers-Danlos Syndrome (hEDS) is the most common type of EDS. Apart from joint symptoms, people with hEDS have systemic manifestations as a chronic modification of the breathing pattern (functional respiratory complaints (FRCs)) and mental disorders. However, the prevalence of FRCs, and its relationship with mental disorders, have not yet been estimated for this population. Objectives To assess the FRCs, central sensitization, disease perception, depression, and anxiety in people with hEDS from Belgium; and to identify the clustering of FRCs and determine any association with the characteristics assessed for this sample. Methods This cross-sectional study assessed socio-demographic characteristics, Nijmegen questionnaire (NQ), Central Sensitization Inventory (CSI), Brief Illness Perception Questionnaire, and the Hospital Anxiety and Depression Scale (HADS) in people with hEDS from Belgium. A two-step cluster analysis was performed to identify clusters according to NQ, and to understand how the other questionnaires are grouped among these clusters. Results The Spearman correlation coefficients showed that all the outcomes were significantly and positively correlated with each other (p<0.05). Furthermore, 84.9% of the sample had symptoms suggestive of FRCs, and 54.3% had probable anxiety. Three clusters were grouped (no FRCs, mild FRCs, and severe FRCs), with NQ, HADS-D and CSI-part A being the variables that contributed the most. People from cluster of severe FRCs got the worst scores for all the questionnaires. Conclusion FRCs, central sensitization, depression, and anxiety are prevalent comorbidities in people with hEDS. Moreover, those people with FRCs had worse results in the investigated parameters, with depression being the variable that contributed the most to the clusters of FRCs. Consequently, investigating mechanisms for these co-occurring symptom profiles may improve our understanding of pathogenesis and indicate new management strategies to alleviate these symptoms and lead to the development of more effective care for persons with hEDS.
Publication
Post-wildfire effects on carbon and water vapour dynamics in a Spanish black pine forest
(Springer, 2015) Dadi , Tarek; Rubio Caballero, Eva María; López Serrano, Francisco Ramón; Andrés Abellán, Manuela; García Morote, Francisco Antonio; Heras Ibáñez, Jorge Antonio de las
Two eddy covariance systems were installed in a high-severity burned zone (BZ) and an adjacent unburned (UNB) zone to monitor water vapour and carbon dioxide fluxes for 21 months (from June 2011 to February 2013) at a Spanish black pine forest affected by a stand-replacing wildfire and located in a mountainous area of central-eastern Spain. The differences between both sites were significant especially during the growing season, affecting gross primary productivity (GPP) more than ecosystem respiration (Reco). Net ecosystem exchange (NEE) for 2012 was -3.97 and 1.80 t C ha-1 year-1 for the unburned and burned sites, respectively, the GPP being 64 % lower for the BZ than the UNB zone. Evapotranspiration (ET) at the UNB was 18 % greater than at the BZ. Difference between sites was 160 mm during the whole studied period. This study reflects the effect of one of the major disturbances that can affect Mediterranean ecosystems, showing that carbon fluxes are more dramatically concerned than water vapour fluxes.
Publication
Is the net primary productivity of coppice forest stands of Quercus ilex ssp. ballota affected by post-fire thinning treatments and recurrent fires?
(Csiro Publishing, 2010) López Serrano, Francisco Ramón; Heras Ibáñez, Jorge Antonio de las; Moya Navarro, Daniel; García Morote, Francisco Antonio; Rubio Caballero, Eva María
Coppice forest stands of Quercus ilex have been one of the forest types most impacted by fire in Spain. After fire, their capability to resprout produces a high density of stems that requires thinning in order to avoid stagnation within the stands. In August 1993 and July 2001, two consecutive fires affected a Quercus ilex coppice stand in SE Spain. This study investigated the effects of different post-fire thinning treatments and recurrent fires on stock and net new carbon increment (NNCI) in a 6-year-old coppice stand. Four degrees of thinning were applied: medium thinning (to a final density of 5000 trees ha–1), drastic thinning (to 1800 trees ha–1), full felling (all trees removed) and no thinning (control). Results showed NNCI was within the lower limit of the average global values reported for net primary productivity of terrestrial ecosystems. The best thinning treatment to maximise both current annual NNCI and mean annual NNCI stimulation, and keep new resprouting within reasonable levels was medium thinning. However, recurrent fires caused the observed net primary productivity to decrease, which allowed us to conclude that stump vitality is affected by successive fires, at least the first year after a new fire.
Publication
EMPLOYMENT OPPORTUNITIES IN SPAIN: GENDER DIFFERENCES BY EDUCATION AND ICT USAGE
(Universidad de Santiago de Compostela. Asociación de Estudios Euro-Americanos de Desarrollo Económico, 2014) Tobarra Gómez, María Ángeles; López Santiago, Luis Antonio; Gómez Sanz, Nuria
Education is a main determinant of employment, but not in isolation. Informationand Communication Technologies (ICT) skills have become a key element to facilitate employment opportunities. The growth in female educational attainment and ICT use is closing the gender divide and favouring female employment. We present evidence on this for the Spanish labour market using: a) a dynamic labour demand function; and b)analyzing the main factors explaining probabilities of finding a job based on traditional characteristics that affect employability and others related to ICT use. We develop this analysis for total population and distinguishing men and women using a Heckman model.