oalib

Publish in OALib Journal

ISSN: 2333-9721

APC: Only $99

Submit

Any time

2019 ( 1051 )

2018 ( 1450 )

2017 ( 1406 )

2016 ( 2020 )

Custom range...

Search Results: 1 - 10 of 813963 matches for " M. A. Barrón-M "
All listed articles are free for downloading (OA Articles)
Page 1 /813963
Display every page Item
Vibration Analysis Of a Self-Excited Elastic Beam
M. A. Barrón-M
Journal of applied research and technology , 2010,
Abstract: The vibration behavior and the energy exchange among the normal modes of a clamped-free self-excited elasticbeam are analyzed in this work. To model this kind of beam, the damping term of a van der Pol oscillator is directlyadded to the equation of a linear elastic beam, yielding a single nonlinear partial differential equation. To solve thisequation, a spectral method is employed. Three vibration modes are considered in the analysis, and the values of theself-exciting constant are varied in order to cover from linear to nonlinear vibration behavior. Multiple frequencies ofthe nonlinear beam are determined through the power spectral density of the beam free-end time series. Given thatthis relatively simple model mimics at least in a qualitative way some key issues of the fluid-structure problem, it couldbe potentially useful for fatigue studies and vibration analysis of rotating blades in turbomachinery.
Comparative anatomy of leaflets of Zamia acuminata and Z. pseudomonticola (Zamiaceae) in Costa Rica
Rafael Acu?a-Castillo,Walter Marín-Méndez
Revista de Biología Tropical , 2013,
Abstract: The genus Zamia is morphologically and ecologically the most diverse of the order Cycadales. Throughout its history this genus has been restricted to the New World and is presently almost entirely restricted to the Neotropics. Unusual anatomical traits of the leaflets, such as the sunken stomata and thick cuticle, are common in this and related genera. The objective of this research was to study and compare the leaflet anatomy of Zamia acuminata and Z. pseudomonticola and establish possible phylogenetic relationships between the anatomical traits and the near relatives of these species. The leaf material was obtained from living plants and then processed for electron microscopy study. We found that both species are very similar to each other and to Z. fairchildiana, and that they share several unusual traits with other species of the genus, such as the parenchyma morphology, the spatial distribution of tissues between the veins and the stomata morphology. The main differences between these species were seen in their fiber clusters and in the abundance of trichome basal cells on the epidermis. The anatomical similarities between the three species could be the result of their close phylogenetic relationship and the divergences between them could be the result of recent speciation during the Pleistocene, resulting from geological changes in Southern Costa Rica. Zamia es morfológica y ecológicamente el género más diverso del orden Cycadales. Este género siempre ha estado restringido a América, pero en la actualidad habita principalmente en la región neotropical. Características anatómicas inusuales en los foliolos como los estomas hundidos y las cutículas gruesas son comunes en Zamia y géneros afines. El objetivo de este trabajo consiste en comparar la anatomía de los foliolos de Zamia acuminata y Z. pseudomonticola y establecer posibles relaciones filogenéticas entre las características anatómicas y los parientes cercanos de esta especie. Las hojas de las especies seleccionadas fueron obtenidas de plantas vivas y luego procesadas para el estudio por microscopía electrónica. Ambas especies son muy similares entre sí y respecto a Z. fairchildiana y comparten varias características en común con otras especies del género como son la morfología del parénquima, de los estomas y la distribución espacial de tejidos alrededor de las haces vasculares. Las diferencias más notables entre especies se vieron a nivel de sus paquetes de fibras y en la abundancia de células basales de los tricomas en la epidermis. Las similitudes anatómicas entre estas tres especies pueden
Una experiencia de aprendizaje incorporando ambientes digitales: competencias básicas para la vida ciudadana
Montero,Leyla María; García-Salazar,Jaime Hernando; Rincón-Méndez,Lida Consuelo;
Educación y Educadores , 2008,
Abstract: the project is based on theoretical assertions by different authors concerning the characteristics of collaborative learning and how they affect the configuration of social networks. a qualitative method was used for the study in which accounts of experiences were examined, together with the results of questionnaires applied to the various individuals who were involved in the process. two digital environments were used throughout the project: simas, for multimedia representations (ontological), and coolmodes, to solve problems in a practical way. a scenario located in the portal colombia aprende was designed to share documents, workshops and proposals as part of the project. thanks to the project, the research group managed to design various ontologies and to develop important work in problem-solving on the coolmodes platform. the products obtained show the levels of comprehension achieved by the students with respect to the topics developed during the process.
Utilización de Sistemas Basados en Reglas y en Casos para dise?ar transmisiones por tornillo sinfín
Moya-Rodríguez,Jorge Laureano; Becerra-Ferreiro,Ana María; Chagoyén-Méndez,César A.;
Ingenier?-a Mec??nica , 2012,
Abstract: nowadays artificial intelligence techniques are applied successfully to different engineering problems, especially the "knowledge based systems". among them the most common are the "frame based systems", "rules based systems", "case based systems" and "hybrid systems". the "case based systems" (cbs) analyze solved problems in an application domain and by means of a process of adaptation; they find the solution to a new problem. these systems can be used successfully for the design of gears, particularly for designing worm gears; nevertheless it constitutes a field of the applications of artificial intelligence even unexplored. a comparison of the use of "rules based system" and "cases based system" for worm gear design is made at this paper. it is also showed the results of applying the "rule based systems to a particular design of a worm gear transmission
Una experiencia de aprendizaje incorporando ambientes digitales: competencias básicas para la vida ciudadana Uma experiência de aprendizagem incorporando ambientes digitais: competências básicas para a vida cidad A Learning Experience Using Digital Environments: Basic Aptitudes for Everyday Living
Leyla María Montero,Jaime Hernando García-Salazar,Lida Consuelo Rincón-Méndez
Educación y Educadores , 2008,
Abstract: El proyecto se apoyó en planteamientos teóricos hechos por diferentes autores, sobre características de los aprendizajes colaborativos y el papel que ellos cumplen en la configuración de las redes sociales. La investigación adoptó un método cualitativo, en el cual se tuvieron en cuenta los relatos de experiencias, junto con los resultados obtenidos en encuestas aplicadas a distintas personas, quienes intervinieron en el proceso. En el proyecto se utilizaron permanentemente dos ambientes digitales: Simas, para hacer representaciones multimediales (ontologías), y Coolmodes, para resolver problemas en forma práctica. En el proyecto se dise ó además un escenario, para compartir documentos, talleres y propuestas, ubicado en el portal Colombia aprende. Como resultado en el proyecto, el grupo investigador logró el dise o de diferentes ontologías y desarrolló un trabajo significativo en el aspecto de resolución de problemas en la plataforma Coolmodes. Los productos obtenidos muestran los niveles de comprensión alcanzados por los estudiantes en los temas desarrollados durante el proceso. O projeto é sustentado em propostas teóricas de vários autores sobre características das aprendizagens cooperativas e o papel que representam na configura o de redes sociais. A pesquisa adotou um método qualitativo em que tiveram-se em conta os relatos de experiências junto com os resultados alcan ados nas sondagens aplicadas a distintas pessoas que intervieram no processo. No projeto, foram usados dois ambientes digitais permanentes: Simas, empregado em fazer representa es de multimídia (ontologias), e Coolmodes, para resolu o prática de problemas. Ademais, foi desenhado um cenário para compartir documentos, oficinas e propostas, situado no portal Col mbia Aprende. The project is based on theoretical assertions by different authors concerning the characteristics of collaborative learning and how they affect the configuration of social networks. A qualitative method was used for the study in which accounts of experiences were examined, together with the results of questionnaires applied to the various individuals who were involved in the process. Two digital environments were used throughout the project: Simas, for multimedia representations (ontological), and CoolModes, to solve problems in a practical way. A scenario located in the portal Colombia Aprende was designed to share documents, workshops and proposals as part of the project. Thanks to the project, the research group managed to design various ontologies and to develop important work in problem-solving on the CoolMo
Geochemistry of modern sediments from San Quintín coastal lagoon, Baja California: Implication for provenance
Daesslé, Luis Walter;Rendón-Márquez, Gabriel;Camacho-Ibar, Víctor F.;Gutiérrez-Galindo, Efraín A.;Shumilin, Evgueny;Ortiz-Campos, Eduardo;
Revista mexicana de ciencias geológicas , 2009,
Abstract: a detailed regional grid of 97 surficial sediment samples is studied for the san quintín coastal lagoon, which is a shallow embayment located adjacent to a "regionally-rare" intraplate-type basaltic terrain known as san quintín volcanic field. the influence that this unique lithology and other potential sources have on the recent sediment geochemistry is discussed on the basis of geochemical, petrographic and sedimentological results. the sandy silts and silts in the lagoon are enriched in ferromagnesian minerals such as pyroxenes and hornblende, which form up to 6 and 22%, respectively, of the total mineral count in the sand fraction. these relatively immature feldspathic sediments are characterized by the presence of abundant angular plagioclase (25-60%) and absence of lithics. the la-sc-th and cr-sc-th discrimination diagrams suggest that mafic ferromagnesian minerals have a significant effect on the geochemical variance of the sediments. the cr/th (median=28) and co/th (median=59) ratios are similar to those reported for sands derived from basic rocks. a mafic provenance is probably responsible for the statistical association of fe, hf, u, th, sc, cr, ca, na and the rare earth elements. an association of fe, organic carbon and total p with the trace elements sb, cr, br, as, na, sc and co indicates that their distribution is mainly controlled by the presence of fe-rich minerals, such as hornblende, and organic matter throughout bahía san quintín and the northernmost bahía falsa, beneath aquaculture racks. low enrichment factors (<1) for cr, sb, as and p indicate that anthropogenic contaminant sources derived from agrochemicals are not significant.
Correlación automatizada de parámetros geométricos mediante contornos de bloqueo en engranajes cilíndricos con contacto exterior
Hernández-Ortega,Robert; Chagoyén-Méndez,César A.; Fernández-Casta?eda,Feliberto; Moya-Rodríguez,Jorge Laureano;
Ingenier?-a Mec??nica , 2013,
Abstract: the aim of this work was to obtain a procedure, that when being implemented in the design software of spur and helical external gears, correlate the geometric parameters automatically by means of the blocking contours making easier the designer's work. the mathematical expressions that define the geometric limitations were transformed so that they can be used in a program that it builds the blocking contour without the designer's intervention. besides that it was settled down the sequence they should be calculated. the procedure was implemented in a calculation program obtaining an execution speed about 1 second. this way it was achieved the automatic correlation of the geometric parameters and a blocking contour construction without the designer's intervention that it shows the values of the addendum modification coefficients of the wheels that can be used.
Photoelectrochemical Properties of Graphene and Its Derivatives
Alberto Adán-Más,Di Wei
Nanomaterials , 2013, DOI: 10.3390/nano3030325
Abstract: Graphene and its derivatives combine a numerous range of supreme properties that can be useful in many applications. The purpose of this review is to analyse the photoelectrochemical properties of pristine graphene, graphene oxide (GO) and reduced graphene oxide (rGO) and their impact on semiconductor catalysts/quantum dots. The mechanism that this group of materials follows to improve their performance will be cleared by explaining how those properties can be exploited in several applications such as photo-catalysts (degradation of pollutants) and photovoltaics (solar cells).
The NASA/IPAC/NExScI Star and Exoplanet Database
G. B. Berriman,B. Ali,R. Baker,K. von Braun,N-M. Chiu,D. R. Ciardi,J. Good,S. R. Kane,M. Kong,A. C. Laity,D. L. McElroy,S. Monkewitz,A. N. Payne,S. Ramirez,M. Schmitz,J. S. Stauffer,P. L. Wyatt
Physics , 2009, DOI: 10.1063/1.3099137
Abstract: The NASA/IPAC/NExScI Star and Exoplanet Database (NStED) is a general purpose stellar archive which supports NASA planet-finding and planet-characterization goals, stellar astrophysics, and the planning of NASA and other space missions. There are two principal components of NStED: a database of 140,000 nearby stars and exoplanet-hosting stars, and an archive dedicated to high precision photometric surveys for transiting exoplanets (NStED-ETSS). We present summaries of these components. The NStED stellar database currently serves published parameters for 140,000 stars. These parameters include coordinates, multiplicity, proper motion, parallax, spectral type, multiband photometry, radial velocity, metallicity, chromospheric and coronal activity index, rotation velocity/period, infrared excess. NStED-ETSS currently serves data from the TrES survey of the Kepler field as well as dedicated photometric surveys of four stellar clusters. NStED-ETSS aims to serve both the surveys and the broader astronomical community by archiving these data and making them available in a homogeneous format.
Applications of Convex Analysis within Mathematics
Francisco J. Aragón Artacho,Jonathan M. Borwein,Victoria Martín-Márquez,Liangjin Yao
Mathematics , 2013,
Abstract: In this paper, we study convex analysis and its theoretical applications. We first apply important tools of convex analysis to Optimization and to Analysis. We then show various deep applications of convex analysis and especially infimal convolution in Monotone Operator Theory. Among other things, we recapture the Minty surjectivity theorem in Hilbert space, and present a new proof of the sum theorem in reflexive spaces. More technically, we also discuss autoconjugate representers for maximally monotone operators. Finally, we consider various other applications in mathematical analysis.
Page 1 /813963
Display every page Item


Home
Copyright © 2008-2017 Open Access Library. All rights reserved.