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Assembly strategies of wind turbine towers for minimum fatigue damage
Nunez-Casado, Cristina,Lopez-Garcia, Oscar,de las Heras, Enrique Gomez,Cuerva-Tejero, Alvaro,Gallego-Castillo, Cristobal Techno-Press 2017 Wind and Structures, An International Journal (WAS Vol.25 No.6
The aim of this paper is to present a method to obtain the dynamic response of a wind turbine tower in time domain by means of the generation of time series and to estimate the associated fatigue damage by means of a Rainflow counting algorithm. The proposed method is based on assuming the vortex shedding is a bidimensional phenomena and on following a classical modal superposition method to obtain the structure dynamic response. Four different wind turbine tower geometric configurations have been analyzed in a range of usual wind velocities and covering extreme wind velocities. The obtained results have shown that, depending on the turbulence intensity and the mean wind velocity, there are tower geometric configurations more advantageous from the fatigue load standpoint. Consequently, the presented model can be utilized to define assembly strategies oriented to fatigue damage minimization.
Academic Environment in the University ; Key to the Mathematical Talent
( Nunez Reinaldo ),( Gomez Bermeo Laura ) 한국수학교육학회 2011 수학교육 학술지 Vol.2011 No.-
The University Sergio Arboleda develops the program of mathematical talents directed to children and youngsters of the basic and intermediate education. One of the conditions of the program is that the students develop the academic activities in the University; the most out-standing students are promoted to taking courses of the undergraduate program in mathematics. During 9 years of experience in the program we have observed that the academic environment of the university has been a positive factor in the motivation, the promotion and development of the talent and has had a favorable influence in the familiar and school environments of the students.
Nunez-Ramirez, Diola Marina,Medina-Torres, Luis,Valencia-Lopez, Jose Javier,Calderas, Fausto,Lopez-Miranda, Javier,Medrano-Roldan, Hiram,Solis-Soto, Aquiles The Korean Society for Microbiology and Biotechnol 2012 Journal of microbiology and biotechnology Vol.22 No.11
Fermentation with filamentous fungi in a bioreactor is a complex dynamic process that is affected by flow conditions and the evolution of the rheological properties of the medium. These properties are mainly affected by the biomass concentration and the morphology of the fungus. In this work, the rheological properties of a fermentation with the fungus Beauveria bassiana under different hydrodynamic conditions were studied and the rheological behavior of this broth was simulated through a mixture of carboxymethyl cellulose sodium and cellulose fibers (CMCNa-SF). The bioreactor was a 10 L CSTR tank operated at different stir velocities. Rheological results were similar at 100 and 300 rpm for both systems. However, there was a significant increase in the viscosity accompanied by a change in the consistence index, calculated according to the power law model, for both systems at 800 rpm. The systems exhibited shear-thinning behavior at all stir velocities, which was determined with the power law model. The mixing time was observed to increase as the cellulose content in the system increased and, consequently, the efficiency of mixing diminished. These results are thought to be due to the rheological and morphological similarities of the two fungal systems. These results will help in the optimization of scale-up production of these fungi.
FOOTPRINT AND MINIMUM DISTANCE FUNCTIONS
Nunez-Betancourt, Luis,Pitones, Yuriko,Villarreal, Rafael H. Korean Mathematical Society 2018 대한수학회논문집 Vol.33 No.1
Let S be a polynomial ring over a field K, with a monomial order ${\prec}$, and let I be an unmixed graded ideal of S. In this paper we study two functions associated to I: The minimum distance function ${\delta}_I$ and the footprint function $fp_I$. It is shown that ${\delta}_I$ is positive and that $fp_I$ is positive if the initial ideal of I is unmixed. Then we show that if I is radical and its associated primes are generated by linear forms, then ${\delta}_I$ is strictly decreasing until it reaches the asymptotic value 1. If I is the edge ideal of a Cohen-Macaulay bipartite graph, we show that ${\delta}_I(d)=1$ for d greater than or equal to the regularity of S/I. For a graded ideal of dimension ${\geq}1$, whose initial ideal is a complete intersection, we give an exact sharp lower bound for the corresponding minimum distance function.
Promoting emotional, social and civic competencies: Educational policies in Spain
Luis Nunez Cubero,Clara Romero Perez 한국교육개발원 2013 KEDI Journal of Educational Policy Vol.10 No.-
This article analyzes Spain’s educational policies in terms of emotional, social, and civic competencies. The need to teach these competencies at school is justified socially and pedagogically, and the way in which these competencies are implemented in Spanish and European school curricula is described. Spain’s main political actions to promote social-emotional education are then described. The article concludes that for these programs to be effective, they must overcome a double challenge related to the practical implementation of competence-based curricula and transversal competencies assessment. Consequently, Europe as well as Spain must redouble their efforts (economic, instrumental, and in terms of assessment) to achieve their educational goals.
NIEBLES-NUNEZ, William,RAMIREZ, Javier,GARCIA-TIRADO, Jhony Korea Distribution Science Association 2022 유통과학연구 Vol.20 No.10
Purpose: This report aimed to review the literature on the research topic "Imports and exports between Colombia and Asian countries in the framework of logistics processes in international trade" of the last ten years. Research design, data and methodology: Documents indexed in the Web of Science metasearch engine were used as a source of information. The 500 most relevant downloaded in bibTex format were worked on and their processing was carried out using the statistical software Excel and R, through the Bibliometrix package. Results: The results indicate that the country that makes the most contributions to the research area is the United States (274), the author that publishes the most is Bahmani-Oskooee M., with (11) research, 424 of the documents found are journal articles, and the institution that contributes the most in this area is the University of Wisconsin. Conclusions: It is concluded that scientific production within the framework of international trade between Asia and Colombia has had a notable increase, which can be explained by the opening of both continents as strategic allies and the new vision of logistics processes taking advantage of the strategic location of countries within the Pacific Ocean.
Assembly strategies of wind turbine towers for minimum fatigue damage
Cristina Nunez-Casado,Oscar Lopez-Garcia,Enrique Gomez de las Heras,Alvaro Cuerva-Tejero,Cristobal Gallego-Castillo 한국풍공학회 2017 Wind and Structures, An International Journal (WAS Vol.25 No.6
The aim of this paper is to present a method to obtain the dynamic response of a wind turbine tower in time domain by means of the generation of time series and to estimate the associated fatigue damage by means of a Rainflow counting algorithm. The proposed method is based on assuming the vortex shedding is a bidimensional phenomena and on following a classical modal superposition method to obtain the structure dynamic response. Four different wind turbine tower geometric configurations have been analyzed in a range of usual wind velocities and covering extreme wind velocities. The obtained results have shown that, depending on the turbulence intensity and the mean wind velocity, there are tower geometric configurations more advantageous from the fatigue load standpoint. Consequently, the presented model can be utilized to define assembly strategies oriented to fatigue damage minimization.
Experimental study of coupled acousticmechanical bandgaps
Daniel Nunez-Solano,Junghwan Kook,Virginia Puyana-Romero 대한기계학회 2023 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.37 No.10
This experimental study investigates the presence of coupled bandgaps for bending and acoustic waves in acoustic-mechanical systems through the analysis of a bandgap structure. The vibrational and acoustic behaviour of a non-planar unit cell with an added acoustic cavity is analyzed using finite element analysis, considering the interaction between acoustics and structure. Band diagrams are utilized to explore the bandgap phenomenon in acoustic, mechanical, and acoustic-structure interaction. Two coupled finite structures, based on specific geometric dimensions, are constructed using a non-planar plate as the mechanical domain, but with different volumes of the acoustic domain. Finite element analysis is employed to evaluate the vibro-acoustic behaviour of these finite structures composed of non-planar unit cells. Additionally, experimental investigations are conducted on micro-milled finite structures to comprehensively analyze the bandgap phenomenon. With these two approaches, the existence of a coupled bandgap is demonstrated, where no wave propagation occurs for both mechanical and acoustic waves. In addition, it is observed that varying the volume of the acoustic domain can adversely affect the coupled bandgap phenomenon. This study contributes valuable insights to the utilization of bandgap structures for vibration reduction in coupled acousticmechanical systems.