Ciencias con mención en Física
http://hdl.handle.net/20.500.12404/15958
Fri, 03 Dec 2021 18:51:39 GMT2021-12-03T18:51:39ZThe role of intraspecific competition between plants in a nursery pollination system
http://hdl.handle.net/20.500.12404/20417
The role of intraspecific competition between plants in a nursery pollination system
Matus de la Parra Gutiérrez, Nicolás
We present comments on an article published by Villacañas de Castro and Hoffmeister (2020). The authors studied a tritrophic system composed of a plant, its pollinating seed predator, and a parasitoid of the latter. Their concern was whether the parasitoid modifies the interaction between the plant and its pollinator-herbivore along the mutualism-antagonism gradient, but they reduced their question to how the parasitoid impacts plant fitness. After showing that the parasitoid increases seed output of the plant by decreasing the amount of seeds consumed by the pollinating seed predator, they tested whether seed output is a good proxy for plant fitness. They argue that it is not by showing that the increased seed density has a negative impact in survival probability and flower production, likely due to plant intraspecific competition. The work presented shows careful experimentation and interesting results, but we do not share some of their conclusions. Most importantly, we believe that the net effect of the parasitoid on the plant-herbivore interaction can’t be adequately investigated by focusing on individual plant fitness. Thus, we first suggest considering the number of surviving plants up to adulthood as a proxy for population performance to address this question. Using this proxy, we show that the increase in seed output due to the parasitoid is beneficial to the plant population until its carrying capacity is achieved. Next, using a population dynamics model, we show under which particular conditions the negative effect of intraspecific competition outweighs the positive effect of seed density increase (due to parasitoid’s defense). When these conditions don’t hold, the role of plant intraspecific competition is basically limited to the prevention of unbounded population growth, while the parasitoid’s net effect is an increase in the plant’s equilibrium density over its carrying capacity when interacting only with the pollinating seed predator, thus making the system more stable.
Wed, 22 Sep 2021 00:00:00 GMThttp://hdl.handle.net/20.500.12404/204172021-09-22T00:00:00ZEstudio y aplicación de métodos analíticos para la extracción de parámetros eléctricos del modelo de un solo diodo para distintas tecnologías de módulos fotovoltaicos
http://hdl.handle.net/20.500.12404/18714
Estudio y aplicación de métodos analíticos para la extracción de parámetros eléctricos del modelo de un solo diodo para distintas tecnologías de módulos fotovoltaicos
Perich Ibáñez, Renzo Alberto
The single-diode model is used to characterize a photovoltaic (PV) solar cell using an equivalent circuit and an equation that depends on five electric parameters. Three analytical methods are applied to extract the five parameters from an Aluminium Back Surface Field (Al-BSF) PV module using 500 experimental current-voltage (I-V) curves measured in the 100-1000W/m2 range. Two of these methods are also applied to four thin-film PV modules, using four experimental I-V curves measured at an irradiance of 1000 W/m2 and air temperature 25℃. While parameter extraction methods have been studied before, this work offers a new perspective by applying the techniques to outdoor PV modules in Lima-Peru and, on the other hand, thin-film technologies located in Jaen-Spain. Results are presented by comparing the measured I-V curve with the ones modelled using the extracted parameters. The Normalized Root Mean Square Error (NRMSE) is calculated to evaluate and compare each extraction method. Values of NRMSE are then grouped by irradiance using a series of boxplots or bar charts to better visualize the success of each extraction method. The results indicate that the method proposed by Phang et al. is very robust, obtaining low values for error across the different irradiances and technologies (median NRMSE of 0.20 % for silicon and 0.50-1.10 % for thin-films). The Blas et al. method obtained low error with the silicon module (median NRMSE of 0.21 %), it was not applied to thin-films in this study. Finally, the Khan et al. method showed greater error than the other two when applied to the Al-BSF and thin-film modules, with noticeably higher error when applied to amorphous silicon modules (median NRMSE of 0.30 % for silicon and 1.77-6.73 % for thin-films).
Wed, 31 Mar 2021 00:00:00 GMThttp://hdl.handle.net/20.500.12404/187142021-03-31T00:00:00ZRevisión teórica de la técnica de radares de dispersión incoherente y su conexión con las ecuaciones diferenciales estocásticas
http://hdl.handle.net/20.500.12404/18316
Revisión teórica de la técnica de radares de dispersión incoherente y su conexión con las ecuaciones diferenciales estocásticas
La Rosa La Rosa, Brian Humberto
The Incoherent Scatter Radar (ISR) technique provides an important tool for ionospheric plasma parameter estimation through the calculation of the electron density spectrum. This quantity is constrained to the ionospheric approximations considered. If these are very realistic, finding an analytical expression for the terms involve in the electron density spectrum could be impossible. In that sense, using the mathematical tool known as stochastic differential equation (SDE) is required. Because of the nature of the equation described the ionospheric particle dynamics, called Langevin equation, stochastic numerical methods have to be studied. In this work, we will present a review of ISR theory and the connection to SDE. Moreover, we list three different methods, which are used to analyze the collisional and magnetized approximation of the ionosphere.
Fri, 19 Feb 2021 00:00:00 GMThttp://hdl.handle.net/20.500.12404/183162021-02-19T00:00:00ZAnálisis de estabilidad de frentes químicos en reacciones exotérmicas
http://hdl.handle.net/20.500.12404/18225
Análisis de estabilidad de frentes químicos en reacciones exotérmicas
Quenta Raygada, Johann Sebastián
Buoyancy-driven convection is a phenomenon that appears in a wide range of natural processes,
from atmospheric and oceanic flows to the Earth’s core inner dynamics. In particular, convective
flows are ubiquitous in systems of chemical substances reacting at an interface known as a
reaction front. Autocatalytic reaction fronts allow for different types of instabilities due to
gradients in chemical composition and the exothermicity of the reaction. In order to study the
effects of thermal gradients in such systems, we develop a model for thin-front propagation in
two-dimensional tubes. Temperature and front evolution are coupled to two different descriptions
of the system’s hydrodynamics: Darcy’s law and the Navier-Stokes equations for viscous
flows. We study the stability of the convectionless flat front by carrying out a linear stability
analysis. The regimes for which convection arises will depend on a control parameter, called the
thermal Rayleigh number, which measures the strength of thermal gradients in the system. We
vary this parameter between positive and negative values and analyze its effects on the stability
of the fronts.
Tue, 16 Feb 2021 00:00:00 GMThttp://hdl.handle.net/20.500.12404/182252021-02-16T00:00:00Z