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Search Results: 1 - 10 of 7898 matches for " Gabriel Plascencia "
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Regulation of the Reacted Layer Thickness in a Gas-Solid Reacting System  [PDF]
Miguel A. Barron, Dulce Y. Medina, Gabriel Plascencia
Intelligent Control and Automation (ICA) , 2014, DOI: 10.4236/ica.2014.53010

A mathematical model for the analysis of a gas-solid reacting system is presented. This model is an alternative to the classical shrinking-core model. The model has a structure that can be easily transformed into a canonical control form, which is proper for controller synthesis. Analytical solution of the model to describe the open-loop behavior is expressed in terms of the Lambert function. The Lambert function is evaluated from aTaylorexpansion series. Besides, a controller is proposed to regulate the reacted layer thickness using initially the diffusion coefficient as control input. The control law is synthesized employing the feedback linearization technique. Main contributions of this work are the synthesis of the layer thickness controller, and the employment of the process temperature as substitute of the diffusion coefficient as the control input.

Numerical Analysis of Oscillation Death in Coupled Self-Excited Elastic Beams
Miguel A. Barron,Isaias Hilerio,Gabriel Plascencia
Advances in Mechanical Engineering , 2012, DOI: 10.1155/2012/746537
Abstract: The emergence of the oscillation death phenomenon in a ring of four coupled self-excited elastic beams is numerically explored in this work. The beams are mathematically represented through partial differential equations which are solved by means of the finite differences method. A coupling scheme based on shared boundary conditions at the roots of the beams is assumed, and as initial conditions, zero velocity of the first beam and three normal vibration modes of a linear elastic beam are employed. The influence of the self-exciting constant on the ring dynamics is analyzed. It is observed that oscillation death arises as result of the singularity of the coupling matrix. 1. Introduction In the past years the collective behavior of coupled nonlinear oscillators has been widely studied in many disciplines, for example, physics [1], biology [2], ecology [3], chemistry [4], and mechanics [5]. A wide diversity of nonlinear dynamic phenomena such as locking [1], partial synchronization [6], full synchronization [7], antiphase synchronization [8], and clustering [9] have been reported in coupled oscillators. Many coupling schemes have also been tested: local [10], nearest [11], global [12], diffusive [13], adaptive [14], delayed [15], hierarchical [16], and so on. An interesting behavior of coupled oscillators is amplitude death and oscillation death, which are steady states where the coupled oscillators stop their oscillation in a permanent way and become frozen in time [17–19]. Sometimes this cessation of oscillations in time is named quenching [20]. Amplitude death arises through a Hopf bifurcation mechanism in coupled oscillators with an important parameter mismatch or in identical oscillators with time delays [21]. An already existing unstable steady state with zero amplitude is transformed by the coupling into a stable one allowing its observation; that is, the coupling induces stability at the origin of the phase space. On the other hand, oscillation death occurs through a saddle-node bifurcation mechanism allowing the emergence of new fixed points: a new stable steady state with nonzero amplitude is created by the coupling [19, 21]. Frequently, in the literature amplitude death is confused with oscillation death [22–27]. Even the famous finding of Lord Rayleigh [28] related to the quenching of two organ pipes standing side by side is indistinctly considered as amplitude death or oscillation death [29]. To date, in spite of the significant conceptual and technical differences between amplitude death and oscillation death, there is not yet a clear
Oxidación de Cu2O a CuO en Aire a Altas Temperaturas Oxidación de óxico cuproso a óxido cúprico en Aire a Altas Temperaturas
Gabriel Plascencia Barrera,Torstein A. Utigard,Tanai Marín Alvarado
Acta Universitaria , 2012,
Abstract: Small Cu2O cylinders were oxidized in a TGA apparatus in air from 850 to 1000 oC. The activation energy for the oxidation kinetics of the cuprous oxide in the temperature range mentioned above was alsoestimated. Cuprous oxide oxidizes according to the cubic law; such kinetic law is explained in terms of the defect concentration within the Cu2O crystal structure. Se oxidó el óxido cuproso a cúprico en aire, en el intervalo de temperatura de 850 a 1000 C ° . El incremento de peso durante la oxidación se determinó mediante termogravimetría. Utilizando los datos de ganancia de peso, se estimó la energía de activación para la oxidación del óxido cuproso. El óxido cuproso se oxida siguiendo la ley cúbica. La ley cúbica se explica a partir de la concentración de defectos cristalinos en el Cu2O.
Influence of the Slag Density on the Splashing Process in a Steelmaking Converter
Miguel A. Barron,Dulce Y. Medina,Isaias Hilerio,Gabriel Plascencia
ISRN Metallurgy , 2014, DOI: 10.1155/2014/525706
Abstract: The way in which slag density influences the slag splashing phenomenon in an oxygen steelmaking converter is numerically analyzed in this work. Several values of the density of the slag are considered, and their effect on the global mass balance and slag average volume fraction on the sidewalls of the converter is studied using isothermal, two-dimensional transient computational fluid dynamics simulations. Diameter of the slag drops is determined from the slag density and the impact velocity of the nitrogen jet. Besides, the effect of the nitrogen jet Mach number on the slag splashing is simulated and discussed. A qualitative comparison between the computer simulations and results from the literature is made. 1. Introduction It is known that the wear of refractory lining in an oxygen steelmaking converter for raw steel manufacturing is a factor which greatly influences the production costs. In the last two decades, slag splashing has emerged as a new technology to extend the lifetime of the converter refractory lining given that this technology reduces the wear associated to thermal and chemical attack by slag and mechanical impact [1, 2]. After the draining of steel, molten slag remaining at the converter bottom is splashed towards the converter sidewalls using a supersonic jet of gaseous nitrogen. Molten slag freezes at the converter walls and forms a protective coating that prevents the wear of the refractory lining. Nitrogen is injected into the converter through a water-cooled vertical lance which has several inclined convergent-divergent nozzles. During the slag splashing process three main stages have been identified in the formation of the slag protective coating: transport of molten slag to the converter walls, adherence of the molten slag to the sidewalls, and freezing and hardening of the slag layer [3]. When the molten slag is transported to the converter sidewalls, two transport mechanisms are present: wash coating and ejection coating [4]. The first one occurs due to the bulk movement of the molten slag to rise above the initial level and the second one due to the ejection of slag droplets which adhere to the vessel sidewalls [5]. In recent years, several experimental studies on the slag splashing phenomenon have been reported. In these studies, physical scale models of the converter are employed, and cold water and air replace molten slag and nitrogen, respectively [4, 6, 7]. In [4] it is reported that large nozzle inclination and lance heights increase the splashing and the main mechanism of splashing changes from ejection to washing as
Liberalización económica y desigualdad salarial en 12 áreas urbanas de México, 1987-2002: la hipótesis de la "U" invertida de Kuznets
Plascencia López, Ismael;
Región y sociedad , 2009,
Abstract: this article analyzes the evolution of income wage inequality, measured by the gini coefficient, in 12 urban areas of mexico- by population and state gross domestic product (gdp)-from 1987 to 2002, and the relationship with other variables associated with the process of economic liberalization, such as commercial openness (co), exports, foreign direct investment (fdi), and gdp by state manufacturer. we contrast the relationship between variables with the kuznets' inverse "u" hypothesis using panel data analysis, cross section and time series in the regional analysis (urban zones and federal states).
Rese a de "The Transnational Capitalist Class" de Leslie Sklair
Ismael Plascencia López
Frontera norte , 2002,
Nota bibliográfica. Crónicas de Nueva York: a propósito de un libro de Alfonso W. Quiroz sobre la corrupción en la historia del Perú
Hugo Pereyra Plascencia
Summa Humanitatis , 2009,
Abstract: no presenta resumen
Propuesta para la medición del desarrollo económico salarial: aplicación en doce de las principales áreas urbanas de México, 1988-2002
Ismael Plascencia López
Papeles de población , 2007,
Abstract: El presente artículo propone la medición deldesarrollo económico salarial de la poblaciónocupada, para ello se analizan doce de lasprincipales áreas urbanas del país, lo anteriorcon el objetivo de avanzar en el análisis de ladesigualdad, haciéndolo más fino ydesagregado. Para ello se construye un índice(IDES) que resume dos componentes, elingreso salarial en términos reales (a precios de2002) y la medición de la igualdad (encontraposición a la desigualdad) a través delcomplemento de Gini (1-Coeficiente de Gini).Para la medición del IDES se utilizó lainformación proporcionada por la EncuestaNacional de Empleo Urbano de 1988 a 2002.Con ello se pretende probar que el impacto dela liberalización económica y aperturacomercial se presenta de forma muydiferenciada al interior de las ciudades.
Liberalización económica y desigualdad salarial en 12 áreas urbanas de México, 1987-2002: la hipótesis de la "U" invertida de Kuznets
Ismael Plascencia López
Región y sociedad , 2009,
Abstract: En este artículo se analiza la evolución de la desigualdad del ingreso salarial, medida por el coeficiente de Gini en 12 áreas urbanas del país -por tama o de población y producto interno bruto (PIB) estatal- de 1987 a 2002, y su relación con otras variables asociadas al proceso de liberalización económica, como la apertura comercial (AC), las exportaciones, la inversión extranjera directa (IED) nacional y el PIB manufacturero estatal. Se contrasta la relación entre variables con la hipótesis de la "U" invertida de Kuznets, mediante datos en panel, corte trasversal y series de tiempo en el análisis regional (zonas urbanas y entidades federativas).
Van Rensselaer Potter, pionero de la ética global
Lilia Benavides Plascencia
Reencuentro , 2012,
Abstract: No estamos relacionados con el mundo en el que vivimos. Necesitamos nuevos valores y un nuevo espíritu para preservar los recursos y todas las formas de vida, no sólo la humana. El crecimiento poblacional, la colonización de los ambientes naturales y la explotación de los recursos naturales nos están conduciendo a un planeta en peligro; es esta la razón que me llevó a presentar en este artículo los dos libros de Van Rensselaer Potter a aquellos no familiarizados con los conceptos de "bioética y ética global", para motivar su lectura y el deseo de cambio hacia un nuevo individuo y una nueva sociedad. Las universidades deben jugar un papel importante en la promoción de un cambio de actitud en los individuos y en las instituciones.
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