Study of a simplified model for DFIG-based wind turbines

In the study of the dynamical behavior of doublyfed induction generators (DFIG), for wind power applications, the use of reduced order models is useful in order to design specific control strategies for wind power plants as well as to obtain lightweight computing simulations. Within this field this paper presents a new dynamic model for wind turbines, based on DFIG, able of representing accurately its behavior during both the steady state and the transient of the grid voltage. As it will be proven this model permits to perform an accurate analysis of the system when there is a voltage dip in the grid. In the following a theoretical study of this model will be carried out and the accuracy of its performance will be tested under different conditions, by means of PSCAD/EMTDC simulations, in order to show its reliability. Finally the reliability of the simplified model will be tested in a scaled experimental setup.Peer ReviewedPostprint (published version

Uso de suplementos nutricionales y ayudas ergogénicas en jugadores profesionales de tenis.

Introduction: Nutritional supplements and ergogenic aids (NS&EA) are used between training/matches with the goal of enhancing tennis performance. Scientific literature about prevalence and use of NS&EA in professional tennis players is scarce. Objective: The aim of the study was to describe the NS&EA used by professional tennis players during a season. Methods: Using a validated self-administered questionnaire, 62 professional male and 9 professional female tennis players (11% in their gender specific top 100 tennis world ranking (i.e., ATP/WTA)) registered all the used NS&EA. Results: Eighty-one percent of the participants declared taking at least one NS&EA. Strength and conditioning trainers (S&C) and tennis coaches were the professionals who recommended most of the NS&EA in the players outside the TOP-100 (OT100; 50.7% and 39.1%, respectively). However, sports nutritionist were the principal advisors in the top-100 tennis players (T100; 62.5%). Sports drinks were the NS&EA most commonly used by all participants (81.7%). T100 participants used caffeine (p = 0.042), creatine (p = 0.001), iron (p = 0.013) and CHO-protein mix (p = 0.033) significantly more frequently that OT100 players. Conclusions: There is a high prevalence of NS&EA use among professional tennis players independently of their tennis ranking position. However, T100 tennis player have an increased use of certain substances such us caffeine, creatine, iron and CHO-Protein mix. For the rest of the studied NS&EA the use was similar between T100 and OT100 players. It is possible that the differences in NS&EA use between groups could be related to the different professionals on charge of nutritional advice in T100 vs OT100.Introducción: los suplementos nutricionales/ayudas ergogénicas (NS&EA) son utilizados en los entrenamientos/partidos de tenis con el objetivo de mejorar el rendimiento. Sin embargo, la literatura científica se encuentras escasos documentos científicos sobre el uso de estas sustancias en tenistas profesionales. Objetivo: describir el uso de NS&EA utilizados por tenistas profesionales durante una temporada. Métodos: se utilizó un cuestionario validado y se evaluó a 62 tenistas profesionales hombres y 9 mujeres (11% entre los 100 mejores del mundo). Resultados: el 81% de los participantes toman al menos un NS&EA. Los preparadores físicos (S&C) y entrenadores de tenis fueron los profesionales preferidos para recomendar NS&EA entre los jugadores fuera del TOP-100 (OT100, 50,7% y 39,1%, respectivamente). Sin embargo, los nutricionistas deportivos fueron los principales asesores de los jugadores entre los 100 mejores del mundo (T100, 62,5%). Las bebidas deportivas fueron los NS&EA más utilizados entre todos los participantes (81,7%). Los tenistas T100 utilizaron cafeína (p = 0,042), creatina (p = 0,001), hierro (p = 0.013) y mezcla de CHO-proteína (p = 0,033) significativamente más frecuentemente que los jugadores OT100. Conclusiones: existe una gran prevalencia de uso de NS&EA entre los tenistas profesionales. Además, los T100 presentan un mayor uso de ciertas sustancias tales como cafeína, creatina, hierro y CHO-proteína. Para el resto de los NS&EA estudiados, el uso fue similar entre los jugadores T100 y OT100. Finalmente, las diferencias en el uso de NS&EA entre grupos pudieran estar relacionadas con los diferentes profesionales escogidos para el asesoramiento nutricional en T100 vs. OT100.post-print691 K

Multi-resonant frequency-locked loop for grid synchronization of power converters under distorted grid conditions

This paper presents a new multiresonant frequencyadaptive synchronization method for grid-connected power converters that allows estimating not only the positive- and negative-sequence components of the power signal at the fundamental frequency but also other sequence components at other harmonic frequencies. The proposed system is calledMSOGI-FLL since it is based on both a harmonic decoupling network consisting of multiple second-order generalized integrators (MSOGIs) and a frequency-locked loop (FLL), which makes the system frequency adaptive. In this paper, the MSOGI-FLL is analyzed for singleand three-phase applications, deducing some key expressions regarding its stability and tuning. Moreover, the performance of the MSOGI-FLL is evaluated by both simulations and experiments to show its capability for detecting different harmonic components in a highly polluted grid scenario.Peer ReviewedPostprint (published version

Usos tradicionales de la vid silvestre euroasiática en la Península Ibérica

The Iberian Peninsula constitutes the Western limit of the dioecious Eurasian wild grapevine (Vitis vinifera L. subsp. sylvestris). At present, it is a threatened plant, due to human impacts. This liana has had different uses in this territory from the Paleolithic until the end of the last century, including several medicinal applications, inherited from the classical Greek culture. In order to retrieve the available written information, we carried out an exhaustive bibliographic search of the pharmacopoeia linked to this Vitaceae, from the 16th century to the present day. Current references on chemical composition of different parts of grapevine and their medicinal uses were also covered. In parallel, we conducted research in several archives and made inquiries to historians, anthropologists, and sanitary personnel. We also interviewed elderly people from rural areas of Spain and Portugal where some relic populations of wild grapevine are still conserved. Among the written and oral medicinal uses compiled, the main ones are: the use of the grapevine bleeding water to alleviate eczema and skin eruptions and to combat conjunctivitis and keratitis; the use of must from unripe berries (agua de agraz in Spanish) as liver tonic and to treat digestive diseases; the leaves were used to reduce edema, as antihemorrhoidal, and for menopausal disorders; and finally, the vinegar was used to clean and disinfect wounds both on humans and animals. This paper highlights the tremendous erosion of the traditional knowledge about this relevant plant genetic resource.La Península Ibérica constituye el límite occidental de la euroasiática y dioica vid silvestre (Vitis vinifera L. subsp. sylvestris). Actualmente la vid silvestre se encuentra amenazada debido al impacto humano. Esta liana tuvo diferentes usos en la península desde el Paleolítico hasta finales del siglo pasado. Entre ellos, como herencia de la cultura griega clásica, aparecen diferentes usos médicos. Para recuperar la información escrita existente, hemos llevado a cabo una búsqueda bibliográfica exhaustiva sobre la farmacopea vinculada a esta Vitaceae, desde el siglo XVI hasta el presente. Incluimos también referencias sobre la composición química de diferentes partes de la vid y sus usos medicinales. Paralelamente, hemos investigado en los archivos de diferentes localidades y realizado consultas a historiadores, antropólogos y personal sanitario. Asimismo, hemos realizado entrevistas a ancianos de diferentes regiones de España y Portugal donde todavía se conservan algunas poblaciones relictas de vid silvestre. Entre la información escrita y oral de los usos medicinales recopilados, mencionaremos el uso del “agua de lloro” de la vid para aliviar eczemas y erupciones cutáneas; para combatir la conjuntivitis y la queratitis; el mosto o “agua de agraz”, como tónico para el hígado y para tratar afecciones digestivas; las hojas para reducir el edema, como antihemorroidales y para trastornos de la menopausia; y por último, el vinagre para limpiar y desinfectar heridas de personas y animales. Este trabajo destaca la tremenda erosión del conocimiento tradicional sobre este recurso fitogenético tan relevante

Caffeine supplementation improves physical performance without affecting fatigue level: a double-blind crossover study.

This study examined the effect of caffeine supplementation (CAFF) in a Wingate test (WT), and the behaviour of blood lactate concentrations (BLa) and neuromuscular fatigue (NMF), measured as reduced countermovement jump (CMJ) performance, in response to the WT. In a double-blind crossover study, 16 participants attended the laboratory twice, separated by a 72-hour window. In the sessions, participants first ingested 6 mg·kg-1 of either CAFF or placebo (PLAC), and then performed a WT. BLa was measured before (L-pre), and 0.5 min (L-post-0.5) and 3.5 min (L-post-3.5) after conducting the WT. The CMJ test was conducted before (CMJ pre), after (CMJ post), and 3 min after completing (CMJ post-3) the WT. The results indicated that CAFF enhanced peak power (Wpeak: + 3.22%; p = 0.040), time taken to reach Wpeak (T_Wpeak: -18.76%; p = 0.001) and mean power (Wmean: + 2.7%; p = 0.020). A higher BLa was recorded for CAFF at L-post-0.5 (+ 13.29%; p = 0.009) and L-post-3.5 (+ 10.51%; p = 0.044) compared to PLAC. CAFF improved peak power (PP; + 3.44%; p = 0.003) and mean power (MP; + 4.78%; p = 0.006) at CMJ pre, compared to PLAC, whereas PP and MP were significantly diminished at CMJ post and CMJ post-3 compared to pre (p < 0.001 for all comparisons) under both the CAFF and PLAC conditions. PP and MP were increased at post-3 compared to post (p < 0.001 for all comparisons) for both conditions. In conclusion, CAFF increased WT performance and BLa without affecting NMF measured by CMJ. Thus, CAFF may allow athletes to train with higher workloads and enhance the supercompensation effects after an adequate recovery period.post-print756 K

Estudio comparativo de los métodos para evaluar la transmitancia térmica en cerramientos opacos en el invierno mediterráneo

In Spain, most of the building stock has an inefficient energy performance. To change this situation, among other aspects, building envelopes must be analysed to change this situation. Thermal transmittance is one of the most significant properties related to building envelopes. However, in-situ evaluation methodologies for this property are designed for cold climates. On the other hand, theoretical methods have a high associated uncertainty. Therefore, it is necessary to study the application of these in situ methods in mild climates such as the Mediterranean one. This study analyses both theoretical and experimental methods. For this purpose, four case studies have been monitored during the winter. Results show that representative results could be obtained with adequate metrological conditions and stable environmental conditions.En España, la mayor parte del parque inmobiliario presenta un comportamiento energético deficiente. Para paliar dicha situación, se debe analizar, entre otros aspectos, su envolvente. De las diferentes propiedades que caracterizan los cerramientos, la transmitancia térmica es una de las más significativas. Sin embargo, las metodologías de evaluación in situ están planteadas para climas fríos, y los métodos teóricos tienen asociados una incertidumbre elevada. Ante esta circunstancia, resulta necesario estudiar su aplicación en climas suaves como el mediterráneo. El presente estudio analizó tanto los métodos teóricos existentes como los experimentales. Para ello se realizó una monitorización sobre cuatro casos de estudio durante el invierno. Los resultados pusieron de manifiesto que, con unas condiciones metrológicas correctas y una estabilidad de las condiciones ambientales, se pueden obtener resultados representativos

Modeling experimental parameters for the fabrication of multifunctional surfaces composed of electrospun pcl/zno-nps nanofibers

In this work, a one-step electrospinning technique has been implemented for the design and development of functional surfaces with a desired morphology in terms of wettability and corrosion resistance by using polycaprolactone (PCL) and zinc oxide nanoparticles (ZnO NPs). The surface morphology has been characterized by confocal microscopy, scanning electron microscopy (SEM), atomic force microscopy (AFM) and water contact angle (WCA), whereas the corrosion resistance has been evaluated by Tafel polarization curves. Strict control over the input operational parameters (applied voltage, feeding rate, distance tip to collector), PCL solution concentration and amount of ZnO NPs have been analyzed in depth by showing their key role in the final surface properties. With this goal in mind, a design of experiment (DoE) has been performed in order to evaluate the optimal coating morphology in terms of fiber diameter, surface roughness (Ra), water contact angle (WCA) and corrosion rate. It has been demonstrated that the solution concentration has a significant effect on the resultant electrospun structure obtained on the collector with the formation of beaded fibers with a higher WCA value in comparison with uniform bead-free fibers (dry polymer deposition or fiber-merging aspect). In addition, the presence of ZnO NPs distributed within the electrospun fibers also plays a key role in corrosion resistance, although it also leads to a decrease in the WCA. Finally, this is the first time that an exhaustive analysis by using DoE has been evaluated for PCL/ZnO electrospun fibers with the aim to optimize the surface morphology with the better performance in terms of corrosion resistance and wettability.Project RTI2018-096262-B-C41–MAITAI, funded by MCIN/AEI/10.13039/501100011033 and, as appropriate, by ERDF 'A way of making Europe'. Grant PRE2019-090656, funded by MCIN/AEI/10.13039/501100011033 and, as appropriate, by ESF 'Investing in your future'. Project PJUPNA1929 funded by MCIN/AEI/10.13039/501100011033 and, as appropriate, by ERDF 'A way of making Europe' and by BEI

Vaccination programs, parity, and calving season as factors affecting the risk of fetal losses and mummified fetuses in Holstein cows

Aim of the study: To investigate vaccination programs, parity, and calving season as factors affecting the risk of abortion and mummified fetuses in Holstein cows.Area of study: Hot zone of Northeast Mexico.Material and methods: Multiple logistic regression models were used to examine the relationship between peripartum disorders, parity, previous occurrence of abortion, season of calving, vaccination program, incidence of abortion, and mummified fetuses in Holstein cows.Main results: For 7014 pregnancies (2886 cows), the percentage of cows aborting and having mummified fetuses was 17.7% and 1.1%, respectively. As the number of brucellosis vaccinations increased, the incidence of abortion increased (10.4% for a single vaccination and 38.0% for 6 accumulated vaccinations). Abortion for cows having 1-2 previous abortions (56%) and &gt;2 abortions (77%) was fivefold and sevenfold greater (p&lt;0.01), respectively, than that for cows without previous abortion. Other important risk factors for abortion were number of calvings (19.8% for nulliparous and primiparous vs. 13.8% for &gt;3 parturitions; OR=1.7, p&lt;0.01), leptospirosis vaccine application &lt;55 days postpartum (dpp; OR=1.3, p&lt;0.05), viral vaccine application &gt;37 dpp (OR=1.3, p&lt;0.01), brucellosis vaccine application &gt;20 dpp (OR=1.6, p&lt;0.01), and no application of clostridial vaccine (OR=3.7, p&lt;0.01). Significant risk factors for mummified fetuses were application of ≥3 brucellosis vaccinations (OR=3.3, p&lt;0.01), no application of 10-way clostridial vaccine (OR=2.3, p&lt;0.01), &gt;2 previous abortions (OR=18.4, p&lt;0.01), and calving in autumn (OR=0.4, compared to winter, p&lt;0.05).Research highlights: Risk of abortion and mummified fetuses in Holstein cows has been found to be related to vaccination programs

Impact response of advance combat helmet pad systems

Combat helmets are designed to protect against ballistic threats and fragments of explosive devices. There are numerous types of helmet comfort foams available. However, pad systems have not been evaluated in combat helmets to understand to what extent they mitigate head accelerations. In this work, different pad systems are studied to analyze the ballistic performance of combat helmets using a Hybrid III dummy equipped with longitudinal accelerometers at the head and a neck simulator. The tests are conducted with 9 mm Full Metal Jacket (FMJ) projectiles according to the performance requirements III-A of the NIJ 0106.01 standard. This experimental methodology allows the evaluation of brain and neck injuries. The thicker bicomponent polyurethane foams and the honeycomb configuration provided the best results in terms of mitigating brain damage due to accelerations applying different criteria (PLA, WSTC, HIC). However, it was concluded that there is no cervical injury or cranial fracture risk for any of the cases studied.The authors acknowledge the Ministry of Economy and Competitiveness of Spain and the FEDER program under Projects DPI2017-88166-R and PID2020-118946RB-I00 for the financial support of the work. M. Rodriguez-Millan acknowledges the Spanish Ministry of Universities, the National Program for the Promotion of Talent, and its Employability in Research and Development and Innovation (R&D&I), National Mobility Subprogram of the National Plan for Scientific and Technical Research and Innovation 2021–2023, for the professor’s mobility program (PRX21/00329). It has to thank the funding for APC: Universidad Carlos III de Madrid (Read and Publish Agreement CRUECSIC 2023).Publicad