231 research outputs found
Molten salt based nanofluids based on solar salt and alumina nanoparticles: An industrial approach
No full textPublisher Copyright: © 2017 Author(s).Thermal Energy Storage (TES) and its associated dispatchability is extremely important in Concentrated Solar Power (CSP) plants since it represents the main advantage of CSP technology in relation to other renewable energy sources like photovoltaic (PV). Molten salts are used in CSP plants as a TES material because of their high operational temperature and stability of up to 600°C. Their main problems are their relative poor thermal properties and energy storage density. A simple cost-effective way to improve the thermal properties of molten salts is to dope them with nanoparticles, thus obtaining the so-called salt-based nanofluids. Additionally, the use of molten salt based nanofluids as TES materials and Heat Transfer Fluid (HTF) has been attracting great interest in recent years. The addition of tiny amounts of nanoparticles to the base salt can improve its specific heat as shown by different authors1-3. The application of these nano-enhanced materials can lead to important savings on the investment costs in new TES systems for CSP plants. However, there is still a long way to go in order to achieve a commercial product. In this sense, the improvement of the stability of the nanofluids is a key factor. The stability of nanofluids will depend on the nature and size of the nanoparticles, the base salt and the interactions between them. In this work, Solar Salt (SS) commonly used in CSP plants (60% NaNO3 + 40% KNO3 wt.) was doped with alumina nanoparticles (ANPs) at a solid mass concentration of 1% wt. at laboratory scale. The tendency of nanoparticles to agglomeration and sedimentation is tested in the molten state by analyzing their size and concentration through the time. The specific heat of the nanofluid at 396 °C (molten state) is measured at different times (30 min, 1 h, 5 h). Further research is needed to understand the mechanisms of agglomeration. A good understanding of the interactions between the nanoparticle surface and the ionic media would provide the tools to avoid agglomeration and sedimentation.We also want to show our gratitude to the STAGE-STE project under the 7th Framework programme and the European Commission for giving us the opportunity to meet Luis Guerreiro from University of Evora and making this collaboration possible. Finally, we show gratitude to the Basque Governement for the economic support given to the Etortek 2014 project on thermal storage and the UPV/EHU for funding the PhD thesis of Belen Munoz Sanchez through Zabalduz research program.Peer reviewe
Proficiency, Attitude and Conventions in Minority Languages
No full textIn this paper we study a simple mathematical model of a bilingual community in which all agents are f luent in the majority language but only a fraction of the population has some degree of pro ficiency in the minority language. We investigate how different
distributions of pro ficiency, combined with the speaker´attitudes towards or against the
minority language, may infl uence its use in pair conversations.The paper was inspired by a working group at the department of Economics I of the University of the Basque Country. The authors bene tted from these discussion. The help of Sergio Faria is gratefully acknowl-
edged. The rst author acknowledges the support of the Spanish Ministerio deEconomía y Competitividad under project ECO2012-31346, and of the Departamento de Educación, Política Lingüística y Cultura from the Basque Government (Research Group IT568-13). The second author acknowledges nancial support from IKERBASQUE, Basque Foundation for Science, through a Research Fellowship, and is grateful to Fundamentos de Análisis Económico I department at UPV/EHU for their hospitality and great research atmosphere.
The third author acknowledges the support of the Advanced Grant NUMERIWAVES/FP7-246775 of the European Research Council Executive Agency, the BERC 2014-2017 program of the Basque Government, the FA9550-15-1-0027 of AFOSR, the MTM2014-52347 and MTM2011-29306 Grants and the Severo Ochoa program SEV-2013-0323 of the MINECO, and a Humboldt Award at the University of Erlangen-Nürnberg
Individual differences in speech imitation/pronunciation aptitude in late bilinguals: functional neuro-imaging and brain morphology
No full textAn unanswered question in adult language learning or late bi- and multilingualism is why individuals show marked differences in their ability to imitate foreign accents. While recent research acknowledges that more adults than previously assumed can still acquire a native foreign accent, very little is known about the neuro-cognitive correlates of this special ability. We investigated 140 German speaking individuals displaying varying degrees of mimicking capacity, based on natural language text, sentence and word imitations either in their second language English or in Hindi and Tamil, languages they had never been exposed to. The large subject pool was extensively controlled for previous language experience prior to magnetic resonance imaging (MRI). The late-onset (around 10 years) bilinguals showed significant individual differences as to how they employed their left-hemisphere speech areas: higher hemodynamic activation in a distinct fronto-parietal network accompanied low ability, while high ability paralleled enhanced gray matter volume in these areas concomitant with decreased hemodynamic responses. Finally and unexpectedly, males were found to be more talented foreign speech mimics
A comprehensive study of the phase segregation of a urea-based phase change material tested under thermal cycling conditions
No full textPublisher Copyright: © 2023Eutectic mixtures are used as PCMs due to the possibility to tailor the melting temperatures and mainly because the phase transition occurs at a unique temperature. Eutectic mixtures are assumed to be congruent melting and solidification materials. Compositional segregation has rarely been reported, when have been researched for its use as PCM. However, the previous premise does not always match the observed facts. The presented work aims to deepen the knowledge regarding the use of eutectic mixtures as PCMs and to determine the influence of operation parameters in the eutectic PCMs potential phase segregation. The eutectic mixture formed by urea and sodium nitrate can be an interesting candidate for use as a phase change material for thermal energy storage in space heating and domestic hot water applications. Nevertheless, the eutectic mixture showed an unforeseen segregation phenomenon when it was exposed to repeated melting-solidification cycles using volumes in the scale of grams. As a result, the phenomenon was studied to determine the potential causes. An experimental campaign was performed to study the urea and sodium nitrate eutectic mixture under different conditions: consisting of thermal cycling using representative masses, and subsequently, the segregated materials and obtained samples were analyzed by different techniques (including XRD, HTXRD, and DSC); and the production of samples under different cooling conditions that were analyzed using microscopy (PLM and SEM). The results established a relationship between the operation conditions, with the resulting crystal structures, which explain the phase segregation in the eutectic mixture. A mitigation measure was determined consisting of mechanical stirring.This work was supported by the Spanish Ministry of Science and Innovation (MICINN) through the Sweet-TES research project ( RTI2018-099557-B-C22 ) and the Consolidated ENEDI Research Group ( IT1730-22 ).The main author wants to thank the financial support of the University of the Basque Country UPV/EHU, through the Personnel Research Training Program to carry out PhD thesis in cotutelle between the University of the Basque country and the Université de Pau et des Pays de l'Adour ( 2016 call ) and Margarita Salas post-doctoral research program from UPV/EHU 2021-2023 call (financed by the European Union - Next generation EU). The authors also greatly appreciate the technical and human support provided by SGiker of UPV/EHU; especially Aitor Larrañaga and Sergio Fernández for their valued help.Peer reviewe
PlanetCam UPV/EHU: a two-channel lucky imaging camera for solar system studies in the spectral range 0.38-1.7 µm
No full textThis is an author-created, un-copyedited version of an article published in Publications of the Astronomical Society of the Pacific. IOP Publishing Ltd is not responsible for any errors or omissions in this version of the manuscript or any version derived from it.We present PlanetCam UPV/EHU, an astronomical camera designed fundamentally for high-resolution imaging of Solar System planets using the “lucky imaging” technique. The camera observes in a wavelength range from 380 nm to 1.7 µm and the driving science themes are atmosphere dynamics and vertical cloud structure of Solar System planets. The design comprises two configurations that include one channel (visible wavelengths) or two combined channels (visible and short wave nfrared) working simultaneously at selected wavelengths by means of a dichroic beam splitter. In this paper the camera components for the two configurations are described, as well as camera performance and the different tests done for the precise characterization of its radiometric and astrometric capabilities at high spatial resolution. Finally, some images of solar system objects are presented as well as photometric results and different scientific cases on astronomical targets.Peer ReviewedPostprint (author's final draft
PlanetCam UPV/EHU: a two-channel lucky imaging camera for solar system studies in the spectral range 0.38-1.7 µm
No full textThis is an author-created, un-copyedited version of an article published in Publications of the Astronomical Society of the Pacific. IOP Publishing Ltd is not responsible for any errors or omissions in this version of the manuscript or any version derived from it.We present PlanetCam UPV/EHU, an astronomical camera designed fundamentally for high-resolution imaging of Solar System planets using the “lucky imaging” technique. The camera observes in a wavelength range from 380 nm to 1.7 µm and the driving science themes are atmosphere dynamics and vertical cloud structure of Solar System planets. The design comprises two configurations that include one channel (visible wavelengths) or two combined channels (visible and short wave nfrared) working simultaneously at selected wavelengths by means of a dichroic beam splitter. In this paper the camera components for the two configurations are described, as well as camera performance and the different tests done for the precise characterization of its radiometric and astrometric capabilities at high spatial resolution. Finally, some images of solar system objects are presented as well as photometric results and different scientific cases on astronomical targets.Peer Reviewe
Proficiency, Attitude and Conventions in Minority Languages
No full textIn this paper we study a simple mathematical model of a bilingual community in which all agents are f luent in the majority language but only a fraction of the population has some degree of pro ficiency in the minority language. We investigate how different
distributions of pro ficiency, combined with the speaker´attitudes towards or against the
minority language, may infl uence its use in pair conversations.The paper was inspired by a working group at the department of Economics I of the University of the Basque Country. The authors bene tted from these discussion. The help of Sergio Faria is gratefully acknowl-
edged. The rst author acknowledges the support of the Spanish Ministerio deEconomía y Competitividad under project ECO2012-31346, and of the Departamento de Educación, Política Lingüística y Cultura from the Basque Government (Research Group IT568-13). The second author acknowledges nancial support from IKERBASQUE, Basque Foundation for Science, through a Research Fellowship, and is grateful to Fundamentos de Análisis Económico I department at UPV/EHU for their hospitality and great research atmosphere.
The third author acknowledges the support of the Advanced Grant NUMERIWAVES/FP7-246775 of the European Research Council Executive Agency, the BERC 2014-2017 program of the Basque Government, the FA9550-15-1-0027 of AFOSR, the MTM2014-52347 and MTM2011-29306 Grants and the Severo Ochoa program SEV-2013-0323 of the MINECO, and a Humboldt Award at the University of Erlangen-Nürnberg
Decentralized platform economy: emerging blockchain-based decentralized platform business models
No full textPublisher Copyright: © 2022, The Author(s), under exclusive licence to Institute of Applied Informatics at University of Leipzig.Emerging decentralized multisided platforms aim to create more open collaborations between participants and question currently centralized networked business models, such as Google, Amazon, Uber, or Airbnb. In this paper, a systematic analysis of the emerging decentralized platform economy is presented based on blockchain technology. The research aims to fill a gap in the literature, as there is currently no specific analyses on these emerging multisided decentralized electronic markets. Eighty-two decentralized platforms were studied. The study contributes to the literature on decentralized platform taxonomy to structure the emerging research domain of decentralized platform business models. Applying a cluster analysis, three emerging archetypes of decentralized platforms were found, referred to as hosted, federated, and shared platform models. The research contributes to a better understanding of emerging decentralized business platforms. According to the findings, two-thirds of the analyzed platforms, namely, federated and shared archetypes, do not follow traditional models. Rather, their aim is to create new business and community relationships. Furthermore, the archetype of shared platforms is the most disruptive, showing a higher level of decentralization and business model change.This work has been partially supported by the Ministry of Science and Innovation (PID2019-105291GB-I00) and by UPV/EHU (GIU20/019).Peer reviewe
Así es la vida: la Medea de Arturo Ripstein. Violencia simbólica y estereotipos de género en el cine
No full textThis paper explores the way that Arturo Ripstein’s film recreates the stereotype of Medea. Using film analysis and based on cultural studies the article asks about the importance and potential power of cinema to recover the ancient myth and show their effects. The analysis expands horizons for the understanding of the mechanisms that link the network of meanings of the film, where the author offers a new vision of Medea's archetype bringing it closer from television formats and popular culture. Medea became in this film the warrior against the symbolic violence. El presente artículo analiza el modo en el que el director mexicano Arturo Ripstein recrea para el cine el estereotipo de Medea. Mediante el análisis fílmico de la película “Así es la vida” y apoyándose en los estudios culturales, el texto se interroga acerca de la importancia y el poder potencial del cine a la hora recuperar el antiguo mito y demostrar su vigencia. El análisis amplía horizontes para la comprensión de los mecanismos que articulan el entramado de significados de la película, donde Ripstein aporta una nueva visión del viejo arquetipo de Medea acercándolo a los formatos procedentes de la cultura popular televisiva. Medea se vislumbra en este análisis como la guerrera contra la violencia simbólica. 
Long-term assessment of the thermal stability of sodium nitrate-urea eutectic phase change material
No full textThe eutectic mixture formed by urea and sodium nitrate can be an interesting candidate for use as a phase change material for thermal energy storage in space heating and domestic hot water applications. It shows a melting point of 85 °C, a melting enthalpy of 172 J/g and a price around 0.9 €/kg. However, the thermal stability of the mixture is a great concern for this application. A preliminary evaluation of the thermal stability was performed and previously reported by the authors. It consisted of an accelerated thermal cycling test with 210 thermal cycles and the material showed a stable behavior. Nevertheless, the long-term stability of urea in the liquid state at temperatures below 100 °C is uncertain and requires a specific study. The main objective of the present work is to evaluate the long-term thermal stability of the mixture when it is exposed to long periods of use under conditions representative of actual applications, by means of analyzing the thermal and compositional behavior of samples remaining at 100 °C for several periods up to one year. A methodology is proposed, which intends to isolate the thermal degradation phenomenon from others, such as phase segregation, supercooling, and polymorphism, that can be introduced by thermal-cycling. It also aims to be more representative of the actual application than the accelerated thermal cycling approach.The authors would like to acknowledge the Ramon Areces Foundation for funding and the Spanish Ministry of Science, Innovation and Universities (MICINN) through the Sweet-TES research project (RTI2018-099557-B-C22). The author Laura Quant wants to thank the financial support of the University of the Basque Country UPV/EHU, through the Personnel Research Training Program to carry out PhD thesis in cotutelle between the University of the Basque country and the Universit ' e de Pau et des Pays de l'Adour (2016 call). Research efforts in this field are also coordinated through the IEA ES Annex 33/SHC Task 58. Finally, the authors greatly thank the technical and human support provided by SGiker of UPV/EHU; especially to Aitor Larranaga, Mamen Sampedro and Alfredo Sarmiento for their valued help
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