2,999 research outputs found

    On the effect of boundaries in two-phase porous flow

    Get PDF
    In this paper we study a model of an interface between two fluids in a porous medium. For this model we prove several local and global well-posedness results and study some of its qualitative properties. We also provide numerics

    Baryon spectroscopy in the unquenched quark model

    Full text link
    We discuss some applications of the unquenched quark model which is an extension of the CQM that includes the effects of sea quarks via a 3P0 quark-antiquark pair-creation mechanism. Particular attention is paid to the electromagnetic couplings and beta decays of baryons. It is shown that the observed discrepancies between the experimental data and the predictions of the CQM can be accounted for in large part by the effects of sea quarks in the unquenched quark model.Comment: 5 pages, 2 figures, 2 tables, invited talk at XVII International Conference on Hadron Spectroscopy and Structure, submitted for publication in Proceedings of Scienc

    Cooperative approach to a location problem with agglomeration economies

    Get PDF
    This paper considers agglomeration economies. A new firm is planning to open a plant in a country divided into several regions. Each firm receives a positive externality if the new plant is located in its region. In a decentralized mechanism, the plant would be opened in the region where the new firm maximizes its individual benefit. Due to the externalities, it could be the case that the aggregated utility of all firms is maximized in a different region. Thus, the firms in the optimal region could transfer something to the new firm in order to incentivize it to open the plant in that region. We propose two rules that provide two different schemes for transfers between firms already located in the country and the newcomer. The first is based on cooperative game theory. This rule coincides with the nucleolus and the t-value of the associated cooperative game. The second is defined directly. We provide axiomatic characterizations for both rules. We characterize the core of the cooperative game. We prove that both rules belong to the core

    Liberalización de los Servicios de Alta Velocidad Ferroviaria en España: El Proceso de Apertura a la Competencia.

    Get PDF
    El objetivo de este trabajo es analizar la apertura a la competencia en España de los trenes de pasajeros de alta velocidad. Formalmente, la liberalización ferroviaria culminó en 2020 con la firma de contratos-marco con tres operadores (Renfe y dos nuevos entrantes), si bien la pandemia sanitaria ha retrasado las fechas planeadas y ha introducido mucha incertidumbre sobre cómo evolucionará este mercado a corto y medio plazo. Tras realizar un análisis de la movilidad en los corredores licitados en todos los modos de transporte, el principal reto identificado es que la nueva oferta prevista parece muy ambiciosa, incluso para la demanda anterior al COVID-19. Si se añaden además los probables cambios en la movilidad post-pandemia, nuestra principal conclusión es que un equilibrio con tres operadores ferroviarios ofertando servicios ferroviarios de alta velocidad en España parece altamente inestable.post-print976 K

    Cooperative approach to a location problem with agglomeration economies

    Get PDF
    This paper considers agglomeration economies. A new firm is planning to open a plant in a country divided into several regions. Each firm receives a positive externality if the new plant is located in its region. In a decentralized mechanism, the plant would be opened in the region where the new firm maximizes its individual benefit. Due to the externalities, it could be the case that the aggregate utility of all firms is maximized in a different region. Thus, the firms in the optimal region could transfer something to the new firm in order to incentivize it to open the plant in that region. We propose two rules that provide two different schemes for transfers between firms already located in the country and the newcomer. The first is based on cooperative game theory. This rule coincides with the τ\tau τ -value, the nucleolus, and the per capita nucleolus of the associated cooperative game. The second is defined directly. We provide axiomatic characterizations for both rules. We characterize the core of the cooperative game. We prove that both rules belong to the core.Xunta de Galicia | Ref. GED431B 2019/34Ministerio de Economía, Industria y Competitividad, Gobierno de España | Ref. ECO2017-82241-RConsejo Nacional de Ciencia y Tecnología | Ref. 438366Ministerio de Economía, Industria y Competitividad, Gobierno de España | Ref. PID2020-113440GB-I0

    Simulación del desempeño de tres perfiles aerodinámicos en flujo turbulento

    Get PDF
    This work presents the lift and drag coefficient curves, as functions of the angle of attack, for the NACA0012, S809 and SG6043 airfoils in turbulent flow conditions. The objective is to identify the airfoil with the best aerodynamic performance under conditions that are descriptive of small scale wind turbine. With the use of OpenFOAM, an analysis was done by numerical simulation. In the case of the NACA0012 airfoil, it was found that the performance is insensitive to the changes in turbulence and the Reynold number. The aerodynamic response of the S809 airfoil is to increase both the drag and lift as the turbulence increases. The SG6043 airfoil responds the best out of the three in turbulent flow, given that the lift curves mostly increase with the turbulence. The curves reported in this work are new and not found in previous literature. Keywords: aerodynamics, lift, drag, turbulence References [1]R. Madriz-Vargas, A. Bruce, M. Watt, L. G. Mogollón and H. R. Álvarez, «Community renewable energy in Panama: a sustainability assessment of the “Bocade Lura” PV-Wind-Battery hybrid power system,» Renewable Energy and Environmental Sustainability, vol. 2, nº 18, pp. 1-7, 2017. https://doi.org/10.1051/rees/2017040. [2]S. Mertenes, «Wind Energy in the Built Environment, » Ph.D. dissertation. Multi-Science, Brentwood, 2006. [3]P. Giguere and M. S. Selig, «New airfoils for small horizontal axis wind turbines,» Journal of Solar Energy Engineering-transactions, vol. 120, pp. 108-114, 1988. https://doi.org/10.1115/1.2888052. [4]A. K. Wright and D. H. Wood, «The starting and low wind speed behaviour of a small horizontal axis wind turbine,» Journal of wind engineering and industrial aerodynamics, vol. 92, nº 14-15, pp. 1265-1279, 2004. https://doi.org/10.1016/j.jweia.2004.08.003. [5]G. Richmond-Navarro, M. Montenegro-Montero and C. Otárola, «Revisión de los perfiles aerodinámicos apropiados para turbinas eólicas de eje horizontal y de pequeña escala en zonas boscosas,» Revista Lasallista de Investigación, vol. 17, nº 1, pp. 233-251, 2020. https://doi.org/10.22507/rli.v17n1a22. [6]A. Tummala, R. K. Velamati, D. K. Sinha, V. Indraja and V. H. Krishna, «A review on small scale wind turbines, » Renewable and Sustainable Energy Reviews,vol. 56, pp. 1351-1371, 2016. https://doi.org/10.1016/j.rser.2015.12.027. [7]L. Pagnini, M. Burlando and M. Repetto, «Experimental power curve of small-size wind turbines in turbulent urban environment,» Applied Energy, vol. 154,pp. 112-121, 2015. https://doi.org/10.1016/j.apenergy. 2015.04.117. [8]W. D. Lubitz, «Impact of ambient turbulence on performance of a small wind turbine,» Renewable Energy, vol. 61, pp. 69-73, 2014. https://doi.org/10.1016/j.renene.2012.08.015. [9]P. Devinant, T. Laverne and J. Hureau, «Experimental study of wind-turbine airfoil aerodynamics in high turbulence, » Journal of Wind Engineering and Industrial Aerodynamics, vol. 90, nº 6, pp. 689-707, 2002. https://doi.org/10.1016/S0167-6105(02)00162-9. [10]C. Sicot, P. Devinant, S. Loyer and J. Hureau, «Rotational and turbulence effects on a wind turbine blade. Investigation of the stall mechanisms,» Journal ofwind engineering and industrial aerodynamics, vol. 96, nº 8-9, pp. 1320-1331, 2008. https://doi.org/10.1016/j.jweia.2008.01.013. [11]C. R. Chu and P. H. Chiang, «Turbulence effects on the wake flow and power production of a horizontal-axis wind turbine,» Journal of Wind Engineering and Industrial Aerodynamics, vol. 124, pp. 82-89, 2014. https://doi.org/10.1016/j.jweia.2013.11.001. [12]Y. Kamada, T. Maeda, J. Murata and Y. Nishida, «Visualization of the flow field and aerodynamic force on a Horizontal Axis Wind Turbine in turbulent inflows,» Energy, vol. 111, pp. 57-67, 2016. https://doi.org/10.1016/j.energy.2016.05.098. [13]Q. A. Li, J. Murata, M. Endo, T. Maeda and Y. Kamada, «Experimental and numerical investigation of the effect of turbulent inflow on a Horizontal Axis WindTurbine (Part I: Power performance),» Energy, vol.113, pp. 713-722, 2016. https://doi.org/10.1016/j.energy.2016.06.138. [14]S. W. Li, S. Wang, J. P. Wang and J. Mi, «Effect of turbulence intensity on airfoil flow: Numerical simulations and experimental measurements,» Applied Mathematics and Mechanics, vol. 32, nº 8, pp. 1029-1038, 2011. https://doi.org/10.1007/s10483-011-1478-8. [15]S. Wang, Y. Zhou, M. M. Alam and H. Yang, «Turbulent intensity and Reynolds number effects on an airfoil at low Reynolds numbers,» Physics of Fluids, vol. 26, nº11, p. 115107, 2014. https://doi.org/10.1063/1.4901969. [16]M. Lin and H. Sarlak, «A comparative study on the flow over an airfoil using transitional turbulence models, » AIP Conference Proceedings, vol. 1738, p.030050, 2016. https://doi.org/10.1063/1.4951806. [17]Langley Research Center, «Turbulence Modelling Resource,» NASA, [Online]. Available: https://turbmodels.larc.nasa.gov/langtrymenter_4eqn.html. [Last access: 08 03 2021].En este trabajo se presentan las curvas de coeficientes de sustentación y arrastre en función del ángulo de ataque, para los perfiles NACA0012, S809 y SG6043 en condiciones de flujo turbulento. El objetivo es identificar el perfil aerodinámico que tiene mejor rendimiento en condiciones de relevancia para las turbinas eólicas de pequeña escala. El análisis se realizó mediante simulación utilizando OpenFOAM. En el caso del perfil NACA0012 se encuentra que su desempeño es poco sensible a cambios en la turbulencia y en el número de Reynolds. La respuesta del perfil S809 es de aumentar tanto el arrastre como la sustentación al aumentar la turbulencia. El desempeño del perfil SG6043 resulta ser el más conveniente en flujo turbulento pues las curvas de sustentación en su mayoría aumentan al aumentar la turbulencia. Las curvas que se reportan aquí son inéditas y no se encuentra en la literatura. Palabras clave: aerodinámica, sustentación, arrastre, turbulencia. Referencias [1]R. Madriz-Vargas, A. Bruce, M. Watt, L. G. Mogollón y H. R. Álvarez, «Community renewable energy in Panama: a sustainability assessment of the “Bocade Lura” PV-Wind-Battery hybrid power system,» Renewable Energy and Environmental Sustainability, vol. 2, nº 18, pp. 1-7, 2017. https://doi.org/10.1051/rees/2017040. [2]S. Mertenes, «Wind Energy in the Built Environment, » Ph.D. dissertation. Multi-Science, Brentwood, 2006. [3]P. Giguere y M. S. Selig, «New airfoils for small horizontal axis wind turbines,» Journal of Solar Energy Engineering-transactions, vol. 120, pp. 108-114, 1988.https://doi.org/10.1115/1.2888052 [4]A. K. Wright y D. H. Wood, «The starting and low wind speed behaviour of a small horizontal axis wind turbine,» Journal of wind engineering and industrial aerodynamics, vol. 92, nº 14-15, pp. 1265-1279, 2004. https://doi.org/10.1016/j.jweia.2004.08.003. [5]G. Richmond-Navarro, M. Montenegro-Montero y C. Otárola, «Revisión de los perfiles aerodinámicos apropiados para turbinas eólicas de eje horizontal y depequeña escala en zonas boscosas,» Revista Lasallista de Investigación, vol. 17, nº 1, pp. 233-251, 2020. https://doi.org/10.22507/rli.v17n1a22. [6]A. Tummala, R. K. Velamati, D. K. Sinha, V. Indraja y V. H. Krishna, «A review on small scale wind turbines, » Renewable and Sustainable Energy Reviews,vol. 56, pp. 1351-1371, 2016. https://doi.org/10.1016/j.rser.2015.12.027. [7]L. Pagnini, M. Burlando y M. Repetto, «Experimental power curve of small-size wind turbines in turbulent urban environment,» Applied Energy, vol. 154,pp. 112-121, 2015. https://doi.org/10.1016/j.apenergy. 2015.04.117. [8]W. D. Lubitz, «Impact of ambient turbulence on performance of a small wind turbine,» Renewable Energy, vol. 61, pp. 69-73, 2014. https://doi.org/10.1016/j.renene.2012.08.015. [9]P. Devinant, T. Laverne y J. Hureau, «Experimental study of wind-turbine airfoil aerodynamics in high turbulence, » Journal of Wind Engineering and Industrial Aerodynamics, vol. 90, nº 6, pp. 689-707, 2002. https://doi.org/10.1016/S0167-6105(02)00162-9. [10]C. Sicot, P. Devinant, S. Loyer y J. Hureau, «Rotational and turbulence effects on a wind turbine blade. Investigation of the stall mechanisms,» Journal ofwind engineering and industrial aerodynamics, vol. 96, nº 8-9, pp. 1320-1331, 2008. https://doi.org/10.1016/j.jweia.2008.01.013. [11]C. R. Chu y P. H. Chiang, «Turbulence effects on the wake flow and power production of a horizontal-axis wind turbine,» Journal of Wind Engineering and Industrial Aerodynamics, vol. 124, pp. 82-89, 2014. https://doi.org/10.1016/j.jweia.2013.11.001. [12]Y. Kamada, T. Maeda, J. Murata y Y. Nishida, «Visualization of the flow field and aerodynamic force on a Horizontal Axis Wind Turbine in turbulent inflows,» Energy, vol. 111, pp. 57-67, 2016. https://doi.org/10.1016/j.energy.2016.05.098. [13]Q. A. Li, J. Murata, M. Endo, T. Maeda y Y. Kamada, «Experimental and numerical investigation of the effect of turbulent inflow on a Horizontal Axis WindTurbine (Part I: Power performance),» Energy, vol.113, pp. 713-722, 2016. https://doi.org/10.1016/j.energy.2016.06.138. [14]S. W. Li, S. Wang, J. P. Wang y J. Mi, «Effect of turbulence intensity on airfoil flow: Numerical simulations and experimental measurements,» Applied Mathematics and Mechanics, vol. 32, nº 8, pp. 1029-1038, 2011. https://doi.org/10.1007/s10483-011-1478-8. [15]S. Wang, Y. Zhou, M. M. Alam y H. Yang, «Turbulent intensity and Reynolds number effects on an airfoil at low Reynolds numbers,» Physics of Fluids, vol. 26, nº11, p. 115107, 2014. https://doi.org/10.1063/1.4901969. [16]M. Lin y H. Sarlak, «A comparative study on the flow over an airfoil using transitional turbulence models, » AIP Conference Proceedings, vol. 1738, p.030050, 2016. https://doi.org/10.1063/1.4951806. [17]Langley Research Center, «Turbulence Modelling Resource,» NASA, [En línea]. Disponible: https://turbmodels.larc.nasa.gov/langtrymenter_4eqn.html. [Último acceso: 08 03 2021]

    Mergers and the outside-in formation of dwarf spheroidals

    Full text link
    We use a cosmological simulation of the formation of the Local Group to explore the origin of age and metallicity gradients in dwarf spheroidal galaxies. We find that a number of simulated dwarfs form "outside-in", with an old, metal-poor population that surrounds a younger, more concentrated metal-rich component, reminiscent of dwarf spheroidals like Sculptor or Sextans. We focus on a few examples where stars form in two populations distinct in age in order to elucidate the origin of these gradients. The spatial distributions of the two components reflect their diverse origin; the old stellar component is assembled through mergers, but the young population forms largely in situ. The older component results from a first episode of star formation that begins early but is quickly shut off by the combined effects of stellar feedback and reionization. The younger component forms when a late accretion event adds gas and reignites star formation. The effect of mergers is to disperse the old stellar population, increasing their radius and decreasing their central density relative to the young population. We argue that dwarf-dwarf mergers offer a plausible scenario for the formation of systems with multiple distinct populations and, more generally, for the origin of age and metallicity gradients in dwarf spheroidals.Comment: 10 pages, 8 figures, Accepted for publication in MNRA
    • …
    corecore