oalib

Publish in OALib Journal

ISSN: 2333-9721

APC: Only $99

Submit

Any time

2017 ( 2 )

2016 ( 1 )

2015 ( 17 )

2014 ( 27 )

Custom range...

Search Results: 1 - 10 of 832 matches for " JAROL; HOYOS "
All listed articles are free for downloading (OA Articles)
Page 1 /832
Display every page Item
EFECTO DE LAS FORMAS DE ONDAS DE CORRIENTE PULSANTE EN LA ELECTRODEPOSITACIóN DE NANOCRISTALES
MOLINA,JAROL; HOYOS,BIBIAN;
DYNA , 2009,
Abstract: a mathematical model has been developed for describing the effect of pulse current wave forms on size and hardness of electroplated nanocrystals. the model relates in a direct form the typical wave variables (frequency, duty cycle and peak current) with harness of generated deposits by means of direct current and by four pulse current wave forms: rectangular, ramp up, ramp down and triangular. the results of the model were evaluated for duty cycles of 20 and 80%, with frequencies of 50 and 150 hz and peak currents of 4 and 8 ka/m2.the model predicts that small increases in the concentration overpotential drives to increase the nucleation rate significantly, diminishing the growth of the nanocrystals and generating a hardness increase. the increase of the duty cycle and the wave?s frequency produces a behavior increasingly close to that produced by direct current, with a diminution in the nanocrystals hardness. any modification in the waveform variables that increases the peak current produces higher hardness values.
EFECTO DE LAS FORMAS DE ONDAS DE CORRIENTE PULSANTE EN LA ELECTRODEPOSITACIóN DE NANOCRISTALES
JAROL MOLINA,BIBIAN HOYOS
DYNA , 2009,
Abstract: Se desarrolló un modelo matemático para establecer el efecto que tiene la forma de las ondas de corriente pulsante en el tama o y dureza de nanocristales electrodepositados. El modelo relaciona de forma directa las variables típicas de las ondas (frecuencia, ciclo de trabajo y corriente pico) con la dureza de los depósitos generados mediante corriente continua y con cuatro tipos de ondas de corriente pulsante: rectangular, rampa ascendente, rampa descendente y triangular. Se evaluaron los resultados del modelo para ciclos de trabajo de 20 y 80%, con frecuencias de 50 y 150 Hz y corrientes pico de 4 y 8 kA/m2. El modelo predice que peque os aumentos en el sobrepotencial de concentración incrementan significativamente la velocidad de nucleación, disminuyen el crecimiento de los nanocristales y generan un aumento en la dureza. El aumento del ciclo de trabajo y la frecuencia de las ondas produce un comportamiento cada vez más cercano al producido por la corriente continua, con una disminución en la dureza de los nanocristales. Cualquier modificación en las variables de las ondas, que tenga como consecuencia el incremento de la corriente pico, produce valores de dureza más altos.
Modelo Matemático de la Nucleación Electroquímica con Ondas de Corriente Pulsante
Molina,Jarol E; Hoyos,Bibian A;
Información tecnológica , 2007, DOI: 10.4067/S0718-07642007000500005
Abstract: a mathematical model has been established for the description of concentration overpotential, nucleation rate and nucleus size formed on metallic substrates when four types of pulse current waveforms are used: rectangular, ramp-down, ramp-up and triangular. the mathematical model was developed considering that the species diffusion in the limit layer is the rate determining step of the process. the model predicts that when using wave current with the same current average and the same time of application, the ramp-down current produces the shortest transition time, with the highest rise of overpotential concentration, this drives to high nucleation rates with small nucleus size. for the case of current wave forms with the same pick and average current, the rectangular and ramp-down waves show practically the same transition time, with equivalent nucleation rate and deposit size.
Modelo Matemático de la Nucleación Electroquímica con Ondas de Corriente Pulsante Mathematical Model for the Electrochemical Nucleation with Pulse Current Waveforms
Jarol E Molina,Bibian A Hoyos
Información Tecnológica , 2007,
Abstract: Se presenta un modelo matemático para describir el sobrepotencial de concentración, la velocidad de nucleación y el tama o de núcleos formados sobre sustratos metálicos, cuando se emplean cuatro tipos de ondas de corriente pulsante: rectangular, rampa ascendente, rampa descendente y triangular. Para el desarrollo del modelo, se considera que la etapa que controla el proceso es la difusión de especies en la capa limite. El modelo predice que, cuando se emplean ondas con igual corriente promedio e igual tiempo de aplicación, la rampa descendente produce tiempos de transición más cortos, con mayor aumento en el sobrepotencial de concentración, lo que lleva a mayores velocidades de nucleación con tama os de núcleos más peque os. Para el caso de ondas con igual corriente pico y promedio, las ondas rectangular y descendente presentan prácticamente el mismo tiempo de transición, con velocidades de nucleación y tama o de los depósitos equivalentes. El modelo desarrollado, constituye una herramienta ágil y flexible para la determinación del tama o y la velocidad de formación de núcleos de electrodepositos y, puede ser extendida para estudiar otro tipo de ondas de corriente. A mathematical model has been established for the description of concentration overpotential, nucleation rate and nucleus size formed on metallic substrates when four types of pulse current waveforms are used: rectangular, ramp-down, ramp-up and triangular. The mathematical model was developed considering that the species diffusion in the limit layer is the rate determining step of the process. The model predicts that when using wave current with the same current average and the same time of application, the ramp-down current produces the shortest transition time, with the highest rise of overpotential concentration, this drives to high nucleation rates with small nucleus size. For the case of current wave forms with the same pick and average current, the rectangular and ramp-down waves show practically the same transition time, with equivalent nucleation rate and deposit size.
European Hazel Shrubs in the Ve ká Fatra Mts: Syntaxonomy and Nome Nclature
Ján Kliment, Ivan Jarolímek
Hacquetia , 2011, DOI: 10.2478/v10028-011-0007-5
Abstract: The core of the article lies in syntaxonomical evaluation of 25 phytocoenological relevés of the European hazel stands from the Ve ká Fatra Mts (Central Slovakia, West Carpathians). These relevés were classified by hierarchical clustering methods and compared with the original diagnoses of relevant associations. The authors suggest the new name for the invalidly described association Lonicero nigrae-Coryletum (Kulczyński 1928) Jurko 1964 (Prenantho purpurei-Coryletum) and set its nomenclatural type (neotype).
To the Validation of the Name Prenantho Purpurei-Coryletum Avellanae: (Hacquetia 10/2: 149-170, 2011)
Ján Kliment, Ivan Jarolímek
Hacquetia , 2012, DOI: 10.2478/v10028-012-0005-2
Abstract:
Generalized liquid volume shifts for the pengrobinson equation of state for the pengrobinson equation of state for C1 to C8 hydrocarbons
Hoyos,B.;
Latin American applied research , 2004,
Abstract: a new generalized correction equation for specific volume of liquid hydrocarbons is proposed. the equation can be used with the peng- robinson equation of state (pr) in a wide temperature range and does not require additional parameters for each substance. the equation has been developed for normal hydrocarbons from methane to octane and the obtained results when it is applied to other substances are analyzed. a comparison is also made with the equation proposed by peneloux et al. (1982) resulting, in all cases, in a better performance of the equation proposed here.
Fenomenología del multiculturalismo y pluralismo intercultural
Hoyos,Guillermo;
Revista Peruana de Medicina Experimental y Salud Pública , 2012, DOI: 10.1590/S1726-46342012000400022
Abstract: multiculturalism is defined as the combination, within a given territory, of a social unit and a cultural plurality by way of exchanges and communications among actors who use different categories of expression, analysis and interpretation. a multiculturalist project should not promote a society that is split up into closed groups; on the contrary, it should set forth policies based on communication and cooperation processes among the cultural communities. to understand this concept, we will present the ontological basis of this phenomenonin the search for a communicational solution, with our startpoint being a phenomenological description of the way in which multiculturalism manifests to us in life; to later deepen into the meaning of the phenomenon,and finally offer a pluralist solution to the problems and challenges cultural differences bring about.
Generalized liquid volume shifts for the pengrobinson equation of state for the pengrobinson equation of state for C1 to C8 hydrocarbons
B. Hoyos
Latin American applied research , 2004,
Abstract: A new generalized correction equation for specific volume of liquid hydrocarbons is proposed. The equation can be used with the Peng- Robinson equation of state (PR) in a wide temperature range and does not require additional parameters for each substance. The equation has been developed for normal hydrocarbons from methane to octane and the obtained results when it is applied to other substances are analyzed. A comparison is also made with the equation proposed by Peneloux et al. (1982) resulting, in all cases, in a better performance of the equation proposed here.
Importación o imposición de una cultura foránea? Las relaciones Estados Unidos - Colombia vistas a través de la historia de la televisión colombiana (1954-1970)
Soraya Hoyos
Historia Crítica , 1990,
Abstract:
Page 1 /832
Display every page Item


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