Empty interior recurrence for continuous flows on surfaces

In this paper we characterize topologically the empty interior subsets of a compact surface S which can be ω-limit sets of recurrent orbits (but of no nonrecurrent ones) of continuous flows on S. This culminates the classification of ω-limit sets for surface flows initiated in [Jiménez & Soler, 2001], [Soler, 2003], [Jiménez & Soler, 2004], and [Jiménez & Soler, 2004b]. We also show that this type of ω-limit sets can always be realized (up to topological equivalence) by smooth flows but cannot be realized by analytic flows.We thank the referee for his/her useful comments on this work which helped us to improve it. This work has been partially supported by Dirección General de Investigación (Subdirección General de Proyectos de Investigación), MICINN, grants BFM2002-03512, MTM2005-03868 and MTM2008- 03679/MTM, and Fundación Séneca (Comunidad Autónoma de la Región de Murcia, Spain), grants PI-8/00807/FS/01, 00684/PI/04 and 08667/PI/08

Pumps as Turbines (PATs) by Analysis with CFD Models

[EN] Pumps as turbines (PATs) are the typical solution for electrification using micro hydropower plants (MHP) in the rural sector. Other engineering applications where lately the use of PATs have increased are irrigation, water supply, and energy recovery systems due to their availability, short delivery time, long service life, economic feasibility, construction, and maintenance advantages. However, selecting the suitable pump(s) is difficult because manufacturers only provide performance curves when operating in pump mode; therefore, there is no universal method to predict that issue. For this reason, theoretical, analytical, experimental, and numerical simulation research have been made to predict these curves and the PATs' performance. The present paper analyzes PATs with Computational Fluid Dynamics (CFD) based on advanced research. For this aim, information from a wide range of types of pumps with different rotation speeds was classified to examine case approaches, computational domains, mesh generation, boundary conditions, optimization of elements, and CFD package used to establish the effectiveness of this tool and to find characteristics which have not been enough investigated at present. Most studies used CFD simulations with ANSYS code and K-¿ turbulence closure model, which presented adequate results. Finally, this paper shows that numerical simulations with CFD analysis were successfully carried out to determine pump performance and predict curves in direct and reverse mode, improving certain components and conducting more profound research on certain specific issues.The authors gratefully acknowledge the financial support provided by Escuela Politécnica Nacional for the development of the project: PIS 19-06, PII-DIM-2019-06, and Process Simulation Laboratory of Mechanical Engineering FacultyPlua, F.; Hidalgo, V.; Cando, E.; Pérez-Sánchez, M.; López Jiménez, PA. (2022). Pumps as Turbines (PATs) by Analysis with CFD Models. International Journal on Advanced Science, Engineering and Information Technology (Online). 12(3):1098-1104. https://doi.org/10.18517/ijaseit.12.3.152901098110412

Prácticas empresariales de excelencia en Internet: la exhibición de logotipos de garantía en los sitios web

En Internet impera cierta sensación de desconfianza. En efecto, no todas las empresas actúan respetando la normativa y aplicando, además, prácticas de excelencia. No obstante, para certificar públicamente que sí resultan fiables, para efectos comerciales determinados sitios web exhiben diferentes logotipos de garantía acreditativos del cumplimiento de exigentes presupuestos de tutela del potencial cliente. Tales prácticas han proliferado a escala internacional. El objetivo del presente artículo es, además de su examen teórico, conocer las razones por las que los empresarios se adhieren a tales logotipos, sus efectos sobre el nivel de transacciones, imagen corporativa y el grado de satisfacción que el empresario tiene respecto a los mismos. Para ello empleamos cuestionarios diseñados específicamente al efecto. Como podrá verse, los sellos resultan especialmente eficaces cuando son conocidos por quienes los observan. En efecto, reducen sensiblemente la sensación de desconfianza que existe en la Red

Efecto de la reducción de soda ASH (NA2CO3) y caliza (CaCO3) sobre las propiedades mecánicas y físicas de vidrios de soda-cal-sílice usados en la manufactura de envases de vidrio y vidrio plano

RESUMEN: La Soda ASH (Na2CO3) es uno de los componentes más importantes para producir vidrio ya que este material es capaz de romper la red de SiO2 y por lo tanto determina importantes propiedades, sin embargo, dicha materia prima también es muy costosa y existe un paradigma al interior de la industria del vidrio concerniente a posibles problemas que se pueden presentar cuando hay disminuciones de Na2O. En este orden de ideas, una disminución progresiva y metodológica de Soda ASH fue desarrollada sobre vidrios fabricados acorde a un diseño de experimentos (DOE), pretendiendo medir y analizar diferentes propiedades mecánicas, físicas y químicas acorde con normas ASTM y procedimientos industriales, obteniendo como resultado cambios estadísticamente no significativos en las propiedades medidas cuando hay disminuciones de hasta el 2.64% en peso de Na2O, lo cual permite pensar en estas disminuciones como una opción para los problemas de la industria del vidrio relacionados con este mineral.ABSTRACT: Soda ASH (Na2CO3) is one of the most important components to produce glass since this material is able to break the SiO2 network and therefore it determines important properties, however it is also so expensive and there is into the glass industry a paradigm regarding possible issues involved with the Na2O decreases. In this order of ideas, a progressive and methodological decrease of Soda ASH was performed over glasses manufactured following a design of experiments (DOE), aiming to measure and to analyze different mechanical, physical and chemical properties according to the respective ASTM standards or industrial procedures, obtaining as a result non-significant statistical changes in all properties measured when there are decreases up to 2.64 wt. % of Na2O, which allows to think about these decreases as an option for the glass industry issues related to this ore

Parametric study of a horizontal axis wind turbine with similar characteristics to those of the Villonaco wind power plant

[EN] The present paper focuses on the selection of parameters that maximize electrical energy production of a horizontal axis wind turbine using Python programming language. The study takes as reference turbines of Villonaco wind field in Ecuador. For this aim, the Blade Element Momentum (BEM) theory was implemented, to define rotor geometry and power curve. Furthermore, wind speeds were analyzed using the Weibull probability distribution and the most probable speed was 10.50 m/s. The results were compared with mean annual energy production of a Villonaco’s wind turbine to validate the model. Turbine height, rated wind speed and rotor radius were the selected parameters to determine the influence in generated energy. Individual increment in rotor radius and rated wind speed cause a significant increase in energy produced. While the increment in turbine’s height reduces energy generated by 0.88%.The authors gratefully acknowledge the financial support provided by Escuela Politécnica Nacional for the development of the project PII-DIM-2019-06Sánchez, S.; Hidalgo, V.; Velasco, M.; Puga, D.; López Jiménez, PA.; Pérez Sánchez, M. (2021). Parametric study of a horizontal axis wind turbine with similar characteristics to those of the Villonaco wind power plant. Journal of Applied Research in Technology & Engineering. 2(2):51-62. https://doi.org/10.4995/jarte.2021.15056OJS516222Adaramola, M. (2014). Wind turbine technology: Principles and design. Apple Academic Press, Inc. https://doi.org/10.1016/s0038-092x(97)82047-6Arconel. (2015). Ecuador posee un 51,78% de energía renovable. https://www.regulacionelectrica.gob.ec/ecuador-posee-un-5155-de-energia-renovable/%0ABakırcı, M., & Yılmaz, S. (2018). Theoretical and computational investigations of the optimal tip-speed ratio of horizontal-axis wind turbines. Engineering Science and Technology, an International Journal, 21(6), 1128-1142. https://doi.org/10.1016/j.jestch.2018.05.006Biadgo, A.M., & Aynekulu, G. (2017). Aerodynamic design of horizontal axis wind turbine blades. FME Transactions, 45(4), 647-660. https://doi.org/10.5937/fmet1704647MBurton, T., Sharpe, D., Jenkins, N., & Bossanyi, E. (2001). Wind Energy Handbook. In Wind Energy Handbook (First edit). Wiley. https://doi.org/10.1002/9781119992714.ch9Carta González, J.A., Calero Pérez, R., Colmenar Santos, A., & Castro Gil, M.A. (2009). Centrales de energías renovables: Generación eléctrica con energías renovables. Pearson Educación S.A.Cochancela, J., & Astudillo, P. (2012). Análisis energético de centrales eólicas. In Universidad de Cuenca. http://dspace.ucuenca.edu.ec/jspui/bitstream/123456789/5022/1/Tesis.pdfCorporación Eléctrica del Ecuador. (2015). Informe de rendición de cuentas 2014 Unidad de Negocio GEN-SUR. https://www.celec.gob.ec/gensur/index.phpCorporación Eléctrica del Ecuador. (2016a). Central Eólica Villonaco genera el 152% de lo planificado CE-LEC EPGENSUR. https://www.celec.gob.ec/gensur/index.php/67-central-eolica-villonaco-genera-el-152-de-lo-planificadoCorporación Eléctrica del Ecuador. (2016b). Informe de rendición de cuentas 2015 Unidad de Negocio GENSUR. https://www.celec.gob.ec/gensur/index.phpCorporación Eléctrica del Ecuador. (2017). Informe de Rendición de Cuentas 2016 Unidad de Negocio GENSUR. https://www.celec.gob.ec/gensur/index.phpCorporación Eléctrica del Ecuador. (2018). Informe de rendición de cuentas 2017 Unidad de Negocio GENSUR. https://www.celec.gob.ec/gensur/index.phpCorporación Eléctrica del Ecuador. (2019a). Informe de rendición de cuentas 2018 Unidad de Negocio GENSUR. https://www.celec.gob.ec/gensur/index.phpCorporación Eléctrica del Ecuador. (2019b). Producción anual de la Central Eólica Villonaco. https://www.celec.gob.ec/gensur/index.php/cev/central-eolica-villonaco-en-cifrasDehouck, V., Lateb, M., Sacheau, J., & Fellouah, H. (2018). Application of the BEM Theory to Design HAWT Blades. Journal of Solar Energy Engineering, Transactions of the ASME, 140(1), 014501. https://doi.org/10.1115/1.4038046Dereje, G., & Sirahbizu, B. (2019). Design and Analysis of 2MW Horizontal Axis Wind Turbine Blade. International Journal of Innovative Science, Engineering & Technology, 6(5).El Khchine, Y., & Sriti, M. (2018). Improved blade element momentum theory (BEM) for predicting the aerodynamic performances of horizontal axis wind turbine blade (HAWT). Technische Mechanik, 38(2), 191-202. https://doi.org/10.24352/UB.OVGU-2018-028Fuglsang, P., Bak, C., Gaunaa, M., & Antoniou, I. (2004). Design and verification of the Risø-B1 airfoil family for wind turbines. Journal of Solar Energy Engineering, Transactions of the ASME, 126(4), 1002-1010. https://doi.org/10.1115/1.1766024Ge, M., Fang, L., & Tian, D. (2015). Influence of reynolds number on multi-objective aerodynamic design of a wind turbine blade. PLoS ONE, 10(11), 1-25. https://doi.org/10.1371/journal.pone.0141848Goldwind. (2015). Goldwind 1.5MW. https://www.goldwindamericas.com/15-mw-pmddGul, M., Tai, N., Huang, W., Nadeem, M.H., & Yu, M. (2019). Assessment of wind power potential and economic analysis at Hyderabad in Pakistan: Powering to local communities using wind power. Sustainability, 11(5), 1391. https://doi.org/10.3390/su11051391Hansen, M.O.L. (2008). Aerodynamics of Wind Turbines (Second ed, Vol. 53, Issue 9). Earthscan.Hidalgo, V., Luo, X.W., Escaler, X., Ji, B., & Aguinaga, A. (2015). Implicit large eddy simulation of unsteady cloud cavitation around a plane-convex hydrofoil. Journal of Hydrodynamics, 27(6), 815-823. https://doi.org/10.1016/S1001-6058(15)60544-3Instituto Nacional de Eficiencia Energética y Energías Renovables. (2014). Análisis del comportamiento de un parque eólico en condiciones extremas.International Energy Agency. (2019). Renewables - World Energy Outlook 2019. https://www.iea.org/reports/world-energy-outlook-2019/renewables#abstractJamieson, P. (2018). Innovation in Wind Turbine Design (Second ed.). Wiley. https://doi.org/10.1002/9781119137924Khaled, M., Mohamed Ibrahim, M., ElSayed Abdel Hamed, H., & Abdel Gawad, A.F. (2017). Aerodynamic Design and Blade Angle Analysis of a Small Horizontal-Axis Wind Turbine. American Journal of Modern Energy, 3(2), 23-27. https://doi.org/10.11648/j.ajme.20170302.12Lanzafame, R., & Messina, M. (2010). Horizontal axis wind turbine working at maximum power coefficient continuously. Renewable Energy, 35(1), 301-306. https://doi.org/10.1016/j.renene.2009.06.020Lee, J.T., Kim, H.G., Kang, Y.H., & Kim, J.Y. (2019). Determining the optimized hub height of wind turbine using the wind resource map of South Korea. Energies, 12(15), 2949. https://doi.org/10.3390/en12152949Letcher, T.M. (2017). Wind Energy Engineering: A Handbook for Onshore and Offshore Wind Turbines. Elsevier. https://doi.org/10.1016/B978-0-12-809451-8.00001-1Mahmood, F.H., Resen, A.K., & Khamees, A.B. (2019). Wind characteristic analysis based on Weibull distribution of AlSalman site, Iraq. Energy Reports, 6(September), 79-87. https://doi.org/10.1016/j.egyr.2019.10.021Mamadaminov, U.M. (2013). Review of Airfoil Structure for Wind Turbine Blades. Department of Electrical Engineering and Renewable Energy REE, 515., September 2013, 1-8.Manwell, J.F., McGowan, J.G., & Rogers, A.L. (2009). Wind energy explained: theory, design and application (Second ed.). John Wiley & Sons. https://doi.org/10.1002/9781119994367Massachusetts Institute of Technology. (2013). Xfoil. https://web.mit.edu/drela/Public/web/xfoil/Mathew, S., & Philip, G.S. (2011). Advances in Wind Energy Conversion Technology. Springer. https://doi.org/10.1007/978-3-540-88258-9Ministerio de Electricidad y Energía Renovable. (2013). Atlas Eólico del Ecuador con fines de generación eléctrica.Mohammadi, M., Mohammadi, A., & Farahat, S. (2016). A new method for horizontal axis wind turbine (HAWT) blade optimization. International Journal of Renewable Energy Development, 5(1), 1-8. https://doi.org/10.14710/ijred.5.1.1-8Najafian Ashrafi, Z., Ghaderi, M., & Sedaghat, A. (2015). Parametric study on off-design aerodynamic performance of a horizontal axis wind turbine blade and proposed pitch control. Energy Conversion and Management, 93, 349-356. https://doi.org/10.1016/j.enconman.2015.01.048Oyedepo, S.O., Adaramola, M.S., & Paul, S.S. (2012). Analysis of wind speed data and wind energy potential in three selected locations in South-East Nigeria. International Journal of Energy and Environmental Engineering, 3(1), 1-11. https://doi.org/10.1186/2251-6832-3-7Rehman, S., Alam, M.M., Alhems, L.M., & Rafique, M.M. (2018). Horizontal Axis Wind Turbine Blade Design Methodologies for Efficiency Enhancement-A Review. Energies, 11(3). https://doi.org/10.3390/en11030506Renewable Energy World. (2019). Wind Power Technology. https://www.renewableenergyworld.com/types-of-renewable-energy/wind-power-tech/#grefRitchie, H., & Roser, M. (2017). Renewable Energy. Our World in Data. https://ourworldindata.org/renewable-energy Saint-Drenan, Y.M., Besseau, R., Jansen, M., Staffell, I., Troccoli, A., Dubus, L., Schmidt, J., Gruber, K., Simões, S.G., &Heier, S. (2019). A parametric model for wind turbine power curves incorporating environmental conditions. Renewable Energy, 157, 754-768. https://doi.org/10.1016/j.renene.2020.04.123Takeyeldein, M.M., Lazim, T.M., Nik Mohd, N.A.R., Ishak, I.S., & Ali, E.A. (2019). Wind turbine design using thin airfoil SD2030. Evergreen Joint Journal of Novel Carbon Resource Sciences & Green Asia Strategy, 6(2), 114-123. https://doi.org/10.5109/2321003Topaloǧlu, F., & Pehlivan, H. (2018). Analysis of Wind Data, Calculation of Energy Yield Potential, and Micrositing Application with WAsP. Advances in Meteorology, 2018. https://doi.org/10.1155/2018/2716868Viscosidad del aire. (2012). https://didactica.fisica.uson.mx/tablas/viscosidad.ht

COMPARACIÓN de la OCURRENCIA poblacional de insectos plagas y BENÉFICOS en areglos de POLICULTIVO y MONOCULTIVO DE TOMATE (Lycopersicum esculentum, Mill), CHILTOMA (Capsicum annum, L.) y MAÍZ (Zea mays, L.)

Este estudio se realizó con el objetivo de comparar el efecto que tienen los asocios de cultivos sobre la ocurrencia de insectos plagas, artrópodos benéficos y el uso equivalente de la tierra. El estudio se estableció en la finca los Toruños, ubicada en el municipio de Tisma-Masaya, llevándose a cabo entre los meses de Junio a Septiembre del 2006. Para el desarrollo de esta investigación se seleccionó una finca representativa de un productor, en donde se establecieron cuatro parcelas, tres parcelas se sembraron con cultivos individuales o monocultivos (tomate, chiltoma, maíz) y una parcela se arregló en forma de policultivo (tomate, chiltoma, maíz). En cada estación se tomaron semanalmente las siguientes variables: número de insectos plagas por planta, número de artrópodos benéficos por planta y el rendimiento de cada cultivo para calcular el uso equivalente de la tierra. En general se observó una menor tendencia de insectos plagas en la parcela de policultivo en comparación con la parcela de monocultivo y a demás se encontró una mayor ocurrencia  poblacional de artrópodos benéficos en la parcela de policultivo en comparación con la parcela de monocultivos. Se calculó el uso equivalente de la tierra y se encontró que los mayores resultados de EUT lo presentaron los arreglos de tomate, chiltoma y maíz en policultivos, con valores de: 1.68, 1.5,1. 16, respectivamente dando como resultado un 68, 50 y 16 por ciento más de producción por unidad de área que los monocultivos. Se concluyó que los arreglos en asocio de cultivos tienen un efecto sobre la ocurrencia poblacional de insectos plagas y artrópodos benéficos y además se hace un mayor uso equivalente de la tierra. Palabras claves: Policultivos, Monocultivos, Insectos plagas, Insectos benéficos, uso equivalente de la tierra

El grado de cultura sobre responsabilidad social empresarial y la protección del medio ambiente en los estudiantes de Ingeniería Industrial, Sistemas e Informática

Objetivo: Analizar el grado de cultura sobre responsabilidad social empresarial en los estudiantes de Ingeniería Industrial, Sistemas e Informática. Métodos: Se aplicó el método deductivo e inductivo. Se utilizó el modelo del diseño de investigación descriptivo correlacional. La población del estudio fue de 1200 estudiantes, del que se calculó un tamaño de muestra final de 235 estudiantes. Resultados: Los indicadores como negocios basados en valores, valores y principios éticos, y gestión responsable sugieren que los estudiantes poseen niveles intermedios de conocimientos, representando a la mayoría con un porcentaje del 59,6%. La variable conciencia en protección del medio ambiente muestra que el 54,9% de los estudiantes son regulares. La pruebas de hipótesis para cada factor arrojaron una significación de muestra de 0,000 (p< 0,05) estableciendo una relación con las variables evaluadas en los estudiantes. Conclusiones: Si existe relación entre el Grado de Cultura sobre Responsabilidad Social Empresarial y la Protección del Medio Ambiente en los estudiantes de la Facultad de Ingeniería Industrial, Sistemas e Informática. Esta relación nos revela la importancia de la cultura de los estudiantes sobre la protección del medio ambiente, de tal manera que se contribuya en nuestra comunidad con el desarrollo sostenible de la economía local y nacional.Palabras clave: Negocios, Valores, principios éticos, gestión responsable, responsabilidad social, protección del medio ambient

Understanding patient-reported knowledge of hernia surgery: a quantitative study

Abdominal wall; Knowledge; PatientPared abdominal; Conocimiento; PacienteParet abdominal; Coneixement; PacientPurpose The objective of this study was to gather information on patient-reported knowledge (PRK) in the field of hernia surgery. Methods A prospective quantitative study was designed to explore different aspects of PRK and opinions regarding hernia surgery. Patients referred for the first time to a surgical service with a presumed diagnosis of hernia and eventual hernia repair were eligible, and those who gave consent completed a simple self-assessment questionnaire before the clinical visit. Results The study population included 449 patients (72.8% men, mean age 61.5). Twenty (4.5%) patients did not have hernia on physical examination. The patient’s perceived health status was “neither bad nor good” or “good” in 56.6% of cases. Also, more patients considered that hernia repair would be an easy procedure (35.1%) rather than a difficult one (9.8%). Although patients were referred by their family physicians, 32 (7.1%) answered negatively to the question of coming to the visit to assess the presence of a hernia. The most important reason of the medical visit was to receive medical advice (77.7%), to be operated on as soon as possible (40.1%) or to be included in the surgical waiting list (35.9%). Also, 46.1% of the patients considered that they should undergo a hernia repair and 56.8% that surgery will be a definitive solution. Conclusion PRK of patients referred for the first time to an abdominal wall surgery unit with a presumed diagnosis of hernia was quite limited and there is still a long way towards improving knowledge of hernia surgery.Open Access Funding provided by Universitat Autonoma de Barcelona

Force–velocity profiles in CrossFit athletes: A cross-sectional study considering sex, age, and training frequency

Introduction: The force–velocity profile has been analysed previously in different sports modalities; nevertheless, it has not been analysed in CrossFit. Objective: The aim of this study was to report neuromuscular characteristics of CrossFit athletes using their individual force-velocity profile, investigating differences according to sex, age, and training frequency. Materials and Meth-ods: 72 males (33.17 ± 6.86 years; BMI: 25.93 ± 3.64 kg/m2) and 18 females (30.11 ± 6.92 years; BMI: 23.53 ± 3.98 kg/m2) participated in this study. The force-velocity profile was calculated using Samo-zino’s method. Furthermore, neuromuscular characterization was completed with a squat jump and three drop jumps (20, 30, and 40 cm). Results: Regarding sex, significant differences in all analysed mechanical variables (p < 0.001) were found except for the theoretical maximal force (p = 0.944). No significant differences were found between age groups. Considering training frequency, athletes who train more than 5 days per week showed higher performance in all analysed mechanical variables (p < 0.05). Conclusion: CrossFit athletes have a force-velocity profile more oriented towards velocity than force. Males and females have different neuromuscular characteristics, also neuromus-cular improvements can be achieved at any age. Moreover, higher neuromuscular performance is developed with a training frequency of 5 days or more per week