Ciencias con mención en Física

Permanent URI for this collectionhttp://98.81.228.127/handle/20.500.12404/15958

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    The role of intraspecific competition between plants in a nursery pollination system
    (Pontificia Universidad Católica del Perú, 2021-09-22) Matus de la Parra Gutiérrez, Nicolás; Stucchi Portocarrero, Luciano
    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.
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    Estudio y aplicación de métodos analíticos para la extracción de parámetros eléctricos del modelo de un solo diodo para distintas tecnologías de módulos fotovoltaicos
    (Pontificia Universidad Católica del Perú, 2021-03-31) Perich Ibáñez, Renzo Alberto; Palomino Töfflinger, Jan Amaru
    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).
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    Revisión teórica de la técnica de radares de dispersión incoherente y su conexión con las ecuaciones diferenciales estocásticas
    (Pontificia Universidad Católica del Perú, 2021-02-19) La Rosa La Rosa, Brian Humberto; Milla Bravo, Marco Antonio
    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.
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    Análisis de estabilidad de frentes químicos en reacciones exotérmicas
    (Pontificia Universidad Católica del Perú, 2021-02-16) Quenta Raygada, Johann Sebastián; Vásquez Rodríguez, Desiderio Augusto
    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.
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    A study of Ultra-High-Energy Cosmic Ray propagation in one-dimensional simulations
    (Pontificia Universidad Católica del Perú, 2021-02-15) Olivares Schneider, José Gabriel; Bazo Alba, José Luis
    Cosmic Rays have come to play an important role in understanding the universe, and astroparticle physics has undergone major developments in the last few decades. As such, several observatories have been set up with the purpose of detecting these particles, and simulation frameworks have been developed in order to further analyze their behavior by creating highly variable environments and parameters. This work covers the essential theory required to study propagation of Ultra- High-Energy Cosmic Rays restricted to linear one-dimensional propagation only; this includes the primary methods of energy loss during propagation, mainly through reactions with the photon background like photo-pion production and photo-disintegration, and additional cosmological effects. The study was done using the CRPropa 3.0 simulation framework. To determine the best possible maximum energy for the simulations, initial trials were done by testing the GZK cutoff for multiple energy values, followed by an analysis of heavier nuclei propagation. As a final complete test run, a model of the cosmic ray spectrum for energies above 1018 eV was made based on two data sets, one made from the average composition of the whole CR energy spectrum, and the other from The Pierre-Auger Observatory measurements for the high energy range. The results showed that initial source composition was the determining factor in the shape of the CR spectrum. These initial simulations done in this work will set the ground for future more complex simulations and studies.
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    Leptonic Modeling of the Multiwavelength Spectra of Astrophysical Sources
    (Pontificia Universidad Católica del Perú, 2021-02-10) Palomino Ylla, Ariadna Uxue; Bazo Alba, José Luis
    This work is motivated by the physical processes which take place in active galactic nuclei (AGN). They are powerful sources of radiation in a wide wavelength. To gain knowledge about these processes, multiwavelength spectral energy distributions (SED) are used. The current work uses three types of distributions applied to two blazars, a variety of AGN objects. The SED of blazars typically has a double-hump structure which can be explained in terms of two models: the hadronic and the leptonic model. A model built only by leptonic processes (in this case, inverse Compton and synchrotron) has proved to be fairly-good to explain the gamma-ray emission from most blazars. The Python package Naima restricts model parameters to find the best fit for the observed data and characterize the source by proposing processes that could take place there. The SEDs of the Mrk 421 and PKS 0537-441 blazars were modelled. The best fits obtained follows an electron differential distribution of the form of an exponential cutoff power law. They have a reduced c2 of 1.92 and 2.58, respectively. For the fitted model for the blazar PKS 0537-441, the radiation of the flux of photons product of the synchrotron process produces the major contribution on the inverse Compton flux.
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    Observación y estudio de (2104) Toronto. Asteroide del cinturón principal
    (Pontificia Universidad Católica del Perú, 2021-02-01) Mujica Cueva, José Umberto; Pajuelo Cubillas, Myriam Virginia
    El Sistema Solar, dentro de las muchas partes que lo componen, alberga en su mayoría asteroides de pequeño tamaño y poco estudio a profundidad, que dentro de su composición u órbitas, pueden revelar pistas sobre cómo es que nuestro entorno planetario se formó, o incluso la existencia de la vida en la Tierra. Basado en ello, el presente trabajo centra su mira en analizar alguno de los cuerpos independientes del cinturón de asteroides, con el fin de observarlo desde un centro astronómico, para luego recolectar imágenes y procesarlas. Debido a la coyuntura sanitaria actual, la toma de datos tuvo que realizarse por parte del equipo del Instituto Astronómico de la Academia Rumana, en su observatorio Berthelot. Es así, que haciendo uso de fotometría diferencial y el programa de uso libre AstroImageJ, se buscará obtener curvas de luz del objeto y entender sus características más importantes, relacionadas a la magnitud, periodo, etc. El trabajo a continuación intenta a su vez contribuir con el incipiente estudio de objetos planetarios en el Perú, trazando como objetivo el poder a futuro realizar las observaciones por cuenta propia y en territorio nacional. Finalmente, tras realizar las gráficas deseadas, se concluye que las imágenes proporcionadas del asteroide (2104) Toronto corresponden a sus características conocidas y el trabajo fue llevado a cabo de manera óptima, demostrando las posibilidades de realizar estudios de este tipo en el país.
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    Estudio de un magnetrón utilizando el método de elementos finitos
    (Pontificia Universidad Católica del Perú, 2021-02-01) Pérez Caro, Erik Alfredo; Torreblanca Quiroz, Humberto
    Magnetron sputtering system is a technique that consists in extracting atoms from a target material by collisions of energetic ions of an inert gas. It is widely used in semiconductor industries and materials processing research for developing thin films by deposition. During this process a low temperature capacitively coupled plasma is generated near the cathode and several variations of the properties of this plasma can affect the thin film deposition process and quality. An approach to study these types of systems is by computational modeling. The use of robust computational codes that can handle complicated geometries and can solve complex systems of differential equations. In this present project we aim to model numerically a system of magnetrons developed at the Materials Science and Renewable Energies (MatER) laboratory. Using the geometry measurements and the material properties of each component taken in the laboratory, a CAD geometry was developed. Furthermore, the electric and magnetic fields are solved for the geometry configuration and, by implementing a Monte Carlo simulation, the electron trajectories and velocity distributions in the system are calculated. Finally, we use a multi-fluid model to solve a simplified system of a 1 dimensional capacitively coupled plasma and recover the system properties. The method to solve the respective system of equations is the finite element method implemented in the software COMSOL Multiphysics.
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    Generación de patrones químicos mediante flujos cortantes
    (Pontificia Universidad Católica del Perú, 2020-10-26) Ledesma Araujo, Angelo Isaac; Vásquez Rodríguez, Desiderio Augusto
    Los sistemas de reacción-difusión permiten la formación de estructuras debido a las distintas difusividades de substancias químicas. Uno de estos sistemas es el de activador-inhibidor presentado en el modelo del Brusselador. En el caso en que este sistema se encuentre en un fluido, requerirá de términos de advección que representan el fenómeno de transporte ocasionado por la velocidad del fluido. Cuando el flujo presenta un esfuerzo de corte, las difusividades efectivas de cada substancia son modificadas, permitiendo invertir las condiciones de estabilidad que permiten la formación de patrones (Vásquez, 2004). En este trabajo se analiza la formación de patrones debido a la advección de un flujo cortante. A través de un flujo de Poiseuille, donde la velocidad tiene dependencia espacial transversal (forma parabólica), se pude violar la condición de formación de patrones de Turing (Vásquez, 2004). Para poder expandir esta investigación y analizar el efecto de un flujo generado por un vórtice, primero se analizará el movimiento caótico generado por vórtices y se caracterizarán diferentes patrones generados por distintos flujos cortantes
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    Desarrollo de un detector juguete basado en el experimento CMS para la búsqueda de partículas neutras con largo tiempo de vida
    (Pontificia Universidad Católica del Perú, 2020-09-11) Coll Saravia, Lucía Ximena; Jones Pérez, Joel
    The Standard Model (SM) of particle physics consists in a description of all the known elemen-tary particles and their interactions. As far as it is known, the SM has passed all experimental tests, but presents some imperfections such as the presence of neutrino masses and the hierarchy problem. This encourages to probe theories beyond the Standard Model (BSM) that could bring solutions to these problems. An interesting proposal is to search for neutral long lived particles (LLP). These type of particles have long decay lengths and can be generated by a variety of BSM models such as Supersymmetry (SUSY), which proposes a solution to the hierarchy problem, and the Seesaw Mechanism that generates massive neutrinos. The detection of the decay products of LLPs would contribute to the discovery of new physics. The objective of this work is to develop a toy detector based on C++ and Pythia8 with the purpose of creating a tool for searches of neutral long lived particles. All the features, including the geometric characteristics and the particle accep- tance are constructed with information from the sub detectors of the CMS experiment. We use a Minimal SUSY process that violates R parity (RPVMSSM) to simulate processes producing LLPs in MadGraph5 and study the response of the toy detector. We conclude our simulation properly recreates important experimental conditions, and is suitable as a first step towards an international competitive particle physics tool.