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Search Results: 1 - 10 of 223517 matches for " Elkin Dario Cárdenas Diaz "
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On Bifurcation of Solutions of the Yamabe Problem in Product Manifolds with Minimal Boundary
Elkin Dario Cárdenas Diaz,Ana Cláudia da Silva Moreira
Mathematics , 2015,
Abstract: In this paper, we study multiplicity of solutions of the Yamabe problem on product manifolds with minimal boundary via bifurcation theory.
Patrón espacial y métodos de muestreo para Frankliniella panamensis en un huerto de ciruelo (Prunus salicina) Spatial pattern and sampling system for Frankliniella panamensis in a plum orchard (Prunus salicina)
Flórez P. Elkin,Numpaque C. Pedro,Corredor P. Dario
Agronomía Colombiana , 1998,
Abstract: El principal objetivo de este trabajo fue el de determinar el patrón espacial de Frankliniella panamensis en un huerto de arboles de ciruelo. Para esto, se evaluaron cuatro sistemas de muestreo: observación directa, golpe de rama, trampa adhesiva (dos tonos de azul, y tonos verde, amarillo y blanco), a dos niveles de altura en el árbol. Adicionalmente, las poblaciones de trips en los árboles de ciruelo fueron correlacionadas con las poblaciones de trips en el muestreo en malezas. El propósito fue establecer nuevas aproximaciones al manejo de plagas. La observación directa, el golpe de rama y la trampa indicaron que el patrón de distribución de los trips es agregado. Sin embargo, el muestreo de malezas arroj6 una distribución al azar en todas las situaciones. Las trampas adhesivas blanca y azul obtuvieron el mayor número de capturas de todos los colores probados. No existieron diferencias significativas entre los dos tonos de azul y el blanco. El sistema de muestreo menos costoso fue el de golpe de rama y este sistema tuvo correlaciones de 1,0 con el sistema de muestreo de malezas. La observación directa y las trampas fueron costosas y tuvieron correlaciones bajas con las poblaciones del muestreo de malezas. La densidad poblacional de F. panamensis tiene una relación estrecha con la fenología de floración de los árboles, y aumentan progresivamente desde el estado de botón hasta caída de los pétalos. El patrón espacial en árboles de ciruelo fue agregado a bajas poblaciones (menos de 11,22 trips/rama) y al azar, para poblaciones altas (más de 11.22 trips/rama). The main objetive of this work was to determine the spatial pattern of Frankliniella. panamensis in a plum orchard. We evaluated four sampling sytems: direct observation, branch shaking, sticky traps (two shades of blue, green, yellow and white), at two leves of height. Additionally, thrips populations in the plum trees were correlated with thrips populations in weeds, to establish new approaches for the pest mangement. Direct observation, branch shaking and sticky traps indicated that the distribution pattern of thrips is aggregated. However, weed sampling indicated a ramdom distribution. White and blue sticky traps had the highest number of captures among all colors tested. There were no differences among the two shades of blue and white. Branch shaking was least expensive system and had a correlation of 1.0 on number of trapped trips using weed sampling. Direct observation and sticky traps were expensive and had a lower correlation with weed sampling. Population density of F. panamensis, has a ve
Life Cycle and Fecundity Analysis of Lutzomyia shannoni (Dyar) (Diptera: Psychodidae)
Ferro Cristina,Cárdenas Estrella,Corredor Dario,Morales Alberto
Memórias do Instituto Oswaldo Cruz , 1998,
Abstract: The life cycle of Lutzomyia shannoni (Dyar), was described for laboratory conditions with maximum daily temperatures of 27-30°C, minimum daily temperatures of 22-27°C and relative humidity between 87-99 %. Life cycle in each stage was as follows: egg 6-12 days (ave. 8.5 days); first stage larva 5-13 days (ave. 9.6 days); second stage larva 4-13 days (ave. 9.2 days ); third stage larva 5-19 days (ave. 11.8 days); fourth stage larva 7-37 days (ave. 19.9 days); pupa 7-32 days (ave. 15.2 days). The life expectancy of adults ranged from 4 to 15 days (ave. 8.6 days). The entire egg to adult period ranged from 36 to 74 days (ave. 54.6 days). On average, each female oviposited 22.7 eggs; the average egg retention per female was 24.3 eggs.
Análisis espacial de las poblaciones de Frankliniella occidentalis (Pergande) en un cultivo de fresa bajo cubierta, como soporte en las decisiones de manejo integrado de plagas Spatial analisis of Frankliniella occidentalis (Pergande) populations in a covered strawberry crop as a support for integrated pest management
Florez Elkin,Corredor Dario
Agronomía Colombiana , 2000,
Abstract: Se estableció la dependencia espacial de Frankliniella occidentalis (Pergande) en un cultivo de fresa bajo cubierta en la Sabana de Bogotá. Se monitorearon las poblaciones de trips por doce semanas, en un área de 8 x 13 cuadrantes (cada cuadrante tenia un área de 8 x 4 m), tomando tres flores por cuadrante. El análisis de datos fue hecho con los programas Surfer y GS+/386, usados en geoestadística, los cuales se basan en el análisis de semivariogramas y correlogramas. Analizamos O;45; 90 y 135 grados de direccionalidad. Se encontraron dependencias espaciales en tres de las doce semanas y éstas indicaron que la dependencia espacial de las poblaciones de trips demostraron limites de uno hasta seis cuadrantes y fueron más frecuentes en O y 45 grados de direccionalidad. No se observó dependencia a 90 grados. Inicialmente, las colonias de trips fueron agregadas, pero cambiaron su disposición espacial al azar a través del tiempo, debido a que los individuos se mueven invadiendo otros cuadrantes. Finalmente, discutimos las importancia de la dependencia espacial de las poblaciones como una herramienta para el manejo de plagas. Spatial dependence of Frankliniella occidentalis (Pergande) in a covered strawberry crop was established at Bogota plateau. Thrips populations were monitored for 12 weeks in an area of eight by 13 quadrants (each quadrant of 8 x 4 m), taking three flowers per quadrant. Data analysis was done with Surfer and GS+/386 programs. Geostatistics, based on semivariogram and correlogram analyses were used. There were analyzed O, 45, 90, and 135 degreed of directionality. Spatial dependence were found in three ofthe twelve weeks and they indicated that spatial dependence of thrips populations showed boundaries from one to six quadrants and were more frequent in Oand 45 degrees of directionality. No dependence was observed at 90 degrees. InitialIy, the thrips colonies were aggregated but, in time, changed this aggregated pattern toward a random pattern due to thrips movement to neighboring quadrants. Finally, we discuss the importance of spatial dependence as a tool for thrips management.
Biocombustibles: búsqueda de alternativas
Cortés Marírr,Elkin Alonso; Ciro Velásquez,Héctor José; Moreno Cárdenas,Edilson León;
CES Medicina Veterinaria y Zootecnia , 2011,
Abstract: today, the world is looking for different alternatives in order to solve the increasing difficulties that face its development, the feeding of its population and, in particular the feeding of developing nations. at the same time, the growing energy demand foreshadows the exhaustion of hydrocarbon reserves in the short and medium term and likewise a significant deterioration of natural resources, especially the contamination of water and the erosion of soil. in order to prevent irreversible changes and reduce the impact of greenhouse gases on the planet's climate, many countries have chosen to gamble on different strategies for the diversification of energy production utilizing renewable energy sources. the replacement of petroleum derived fuel with biofuels provides a reduction in co2 emissions generated by vehicles. this appears to indicate that the biofuels could potentially be an option, but one not without questions. the new agro-energy industry, unlike that of the oil industry, involves a production chain that impacts more directly the different sectors of the economy, especially the generation of employment, agricultural development and the agro-industry. the addition of biofuels to fuel mixtures can partially mitigate the need for the importation of hydrocarbons, which furthers the national biofuel policy versus energy trade balance, and to a certain extent defines the parameters for security at the supply level. the goal of this paper is to assess the possible scenario of replacement of the current energy matrix with vegetable derived alternative products.
Life Cycle and Fecundity Analysis of Lutzomyia shannoni (Dyar) (Diptera: Psychodidae)
Ferro, Cristina;Cárdenas, Estrella;Corredor, Dario;Morales, Alberto;Munstermann, Leonard E;
Memórias do Instituto Oswaldo Cruz , 1998, DOI: 10.1590/S0074-02761998000200011
Abstract: the life cycle of lutzomyia shannoni (dyar), was described for laboratory conditions with maximum daily temperatures of 27-30°c, minimum daily temperatures of 22-27°c and relative humidity between 87-99 %. life cycle in each stage was as follows: egg 6-12 days (ave. 8.5 days); first stage larva 5-13 days (ave. 9.6 days); second stage larva 4-13 days (ave. 9.2 days ); third stage larva 5-19 days (ave. 11.8 days); fourth stage larva 7-37 days (ave. 19.9 days); pupa 7-32 days (ave. 15.2 days). the life expectancy of adults ranged from 4 to 15 days (ave. 8.6 days). the entire egg to adult period ranged from 36 to 74 days (ave. 54.6 days). on average, each female oviposited 22.7 eggs; the average egg retention per female was 24.3 eggs.
The seismic and hydroacoustic stations on Socorro Island: Early results
Valenzuela, Raúl W.;Pacheco, Javier F.;Pereira, José;Estrada, Jorge A.;Pérez, Jesús A.;Cruz, José L.;Baturan, Dario;Cárdenas, Arturo;Santiago, José A.;
Geofísica internacional , 2007,
Abstract: a seismic and hydroacoustic network on socorro island was installed jointly by the servicio sismológico nacional, instituto de geofísica, universidad nacional autónoma de méxico, and the comprehensive nuclear-test-ban treaty organization. the detection of ten earthquakes in june and july 2004 is reported in this study. these events occurred at epicentral distances between 209 and 9050 km and ranged in magnitude between 3.9 and 6.8. an event in the kamchatka peninsula featured arrivals of teleseismic high-frequency p and pp waves from a distance of 8245 km. an earthquake in the guerrero-oaxaca, mexico, region shows clear seismic and t phases. three earthquakes in the rivera fracture zone were recorded, thus leading to the expectation of the continued detection of events from nearby fracture zones as well as earthquakes generated by volcanoes on socorro and san benedicto islands. the analysis of the t phases from several events validates the design of the network, with three sites around the island in order to record arrivals from all directions. high frequency seismic waves generated by acoustic waves attenuate as they propagate through the rock from one end of the island to the other. consequently small or distant events are difficult to detect at the far side of the island.
An Iterative Method for Solving Two Special Cases of Lane-Emden Type Equation  [PDF]
Pedro Pablo Cárdenas Alzate
American Journal of Computational Mathematics (AJCM) , 2014, DOI: 10.4236/ajcm.2014.43021
Abstract:

In this work we apply the differential transformation method or DTM for solving some classes of Lane-Emden type equations as a model for the dimensionless density distribution in an isothermal gas sphere \"\" and as a study of the gravitational potential of (white-dwarf) stars ,\"\" which are nonlinear ordinary differential equations on the semi-infinite domain [1] [2]. The efficiency of the DTM is illustrated by investigating the convergence results for this type of the Lane-Emden equations. The numerical results show the reliability and accuracy of this method.

A Survey of the Implementation of Numerical Schemes for Linear Advection Equation  [PDF]
Pedro Pablo Cárdenas Alzate
Advances in Pure Mathematics (APM) , 2014, DOI: 10.4236/apm.2014.48052
Abstract:

The interpolation method in a semi-Lagrangian scheme is decisive to its performance. Given the number of grid points one is considering to use for the interpolation, it does not necessarily follow that maximum formal accuracy should give the best results. For the advection equation, the driving force of this method is the method of the characteristics, which accounts for the flow of information in the model equation. This leads naturally to an interpolation problem since the foot point is not in general located on a grid point. We use another interpolation scheme that will allow achieving the high order for the box initial condition.

A Survey of the Implementation of Numerical Schemes for the Heat Equation Using Forward Euler in Time  [PDF]
Pedro Pablo Cárdenas Alzate
Journal of Applied Mathematics and Physics (JAMP) , 2014, DOI: 10.4236/jamp.2014.213135
Abstract: We establish the conditions for the compute of the Global Truncation Error (GTE), stability restriction on the time step and we prove the consistency using forward Euler in time and a fourth order discretization in space for Heat Equation with smooth initial conditions and Dirichlet boundary conditions.
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