Development of Magnetostrictive Transducer Prototype for Blockage Detection on Molten Salt Pipes

In solar thermal power plants molten salt is often used to store and transport the energy that is collected during the day. The external pipe temperature is measured to activate an electric heating system if the temperature approaches the melting point. However, salt solidification cannot be completely excluded from the plant management. Once occurred, the location of a salt blockage is very complex due to the high temperature of the pipe. Therefore, when this problem arises, power plants have to stop production with the consequences in time and cost that this entails. Electro-magnetic acoustic transducers can be used as non-destructive testing systems for this application. A method for salt blockage detection is proposed that is applicable in straight sections of pipes by employing torsional guided waves that are generated with magnetostrictive transducers. The present paper deals with the transducer conception and the design of the power supply to activate it. Two alternatives are proposed and compared to determine the improvement in the amplitude/noise ratio. Finally, the experimental results show the performance of the equipment in a small prototype, thus validating the technique presented

LCC Resonant Multilevel Converter for X-ray Applications

Medical X-ray appliances use high-voltage power supplies that must be able to work with very different energy requirements. Two techniques can be distinguished in X-ray medical imaging: fluoroscopy and radioscopy. The former involves low power radiation with a long exposure time, while radioscopy requires large power during short radiographic exposure times. Since the converter has to be designed by taking into account the maximum power specification, it will exhibit a poor efficiency when operating at low power levels. Such a problem can be solved by using a new multilevel LCC topology. This topology is based on a classical series-parallel resonant topology, but includes an additional low-voltage auxiliary transformer whose function depends on the X-ray technique considered. When radioscopy operation is selected, the transformer will allow the power to be shared between two full-bridges. If fluoroscopy mode is activated, the auxiliary full bridge is disconnected and the magnetizing inductance of the auxiliary transformer is used to increase the resonant inductor in order to reduce the resonant currents, thus improving the efficiency of the converte

MANIOBRAS EN TELDE [Material gráfico]

FOTO SOBRE PAPEL DE GRUPO DE MILITARES "EN EL MOMENTO DE DISPARAR UNA PIEZA DE MONTAÑA" TELDE 23/03/1915.¿1905 Ó 1915?Copia digital. Madrid : Ministerio de Educación, Cultura y Deporte. Subdirección General de Coordinación Bibliotecaria, 201

Treatment with tocilizumab or corticosteroids for COVID-19 patients with hyperinflammatory state: a multicentre cohort study (SAM-COVID-19)

Objectives: The objective of this study was to estimate the association between tocilizumab or corticosteroids and the risk of intubation or death in patients with coronavirus disease 19 (COVID-19) with a hyperinflammatory state according to clinical and laboratory parameters. Methods: A cohort study was performed in 60 Spanish hospitals including 778 patients with COVID-19 and clinical and laboratory data indicative of a hyperinflammatory state. Treatment was mainly with tocilizumab, an intermediate-high dose of corticosteroids (IHDC), a pulse dose of corticosteroids (PDC), combination therapy, or no treatment. Primary outcome was intubation or death; follow-up was 21 days. Propensity score-adjusted estimations using Cox regression (logistic regression if needed) were calculated. Propensity scores were used as confounders, matching variables and for the inverse probability of treatment weights (IPTWs). Results: In all, 88, 117, 78 and 151 patients treated with tocilizumab, IHDC, PDC, and combination therapy, respectively, were compared with 344 untreated patients. The primary endpoint occurred in 10 (11.4%), 27 (23.1%), 12 (15.4%), 40 (25.6%) and 69 (21.1%), respectively. The IPTW-based hazard ratios (odds ratio for combination therapy) for the primary endpoint were 0.32 (95%CI 0.22-0.47; p < 0.001) for tocilizumab, 0.82 (0.71-1.30; p 0.82) for IHDC, 0.61 (0.43-0.86; p 0.006) for PDC, and 1.17 (0.86-1.58; p 0.30) for combination therapy. Other applications of the propensity score provided similar results, but were not significant for PDC. Tocilizumab was also associated with lower hazard of death alone in IPTW analysis (0.07; 0.02-0.17; p < 0.001). Conclusions: Tocilizumab might be useful in COVID-19 patients with a hyperinflammatory state and should be prioritized for randomized trials in this situatio

Post-reguladores de alto rendimiento para la mejora de las características dinámicas de convertidores con corrección de factor potencia

La necesidad de cumplimiento de normas de inyección de armónicos de baja frecuencia ha impulsado el desarrollo y estudio de nuevas topologías de convertidores ca/cc y ca/ca que permitan satisfacer dichas normas a mínimo coste de rendimiento, fiabilidad, precio, dimensiones y peso. Existe un amplio abanico de soluciones propuestas que permiten escoger la más adecuada en funciónd e cuál de los anteriores parametros pese más en la decisión final. Una de las mejores soluciones consiste en conectar a la red un primer convertidor, llamado emulador de resistencia er, que consigue que la corriente demandada se asenoidal. Como es conocido, uno de los inconvenientes del er es que su dinámica es necesariamente lenta, ya que el lazo de control tiene que filtrar el rizado de 100 hz presente en el condensador de salida. Con el fin de mejorar estas características y al mismo tiempo reducir el tamaño del condensador de filtro, se hace necesario añadir una segunda etapa, lo que penaliza el rendimiento de la cadena conversora. En el presente trabajo doctoral se pretende realizar algunas aportaciones en el campo de los circuitos post-reguladores utilizados coner. Como paso previo a la realización de este trabajo se ha dado un reapso a la situación actual en la corrección del factor de potencia en sistemas de alimentación monofásicos. Dentro de la filosofía de utilizar circuitos post-reguladores que no penalicen en exceso el rendimiento global de la cadena conversosra, se presentan varias alternativas. Se persiguen dos objetivos en este trabajo. El primero dirigido hacia el estudio y ensayo de nuevas topologías de potencia para ser utilizadas como post-reguladores de alto rendimiento. Y finalmente el segundo encaminado a realizar un estudio sobre la problemática de la conexión en cascada de dos etapas de potencia