3 research outputs found

    Brownian Motion in wedges, last passage time and the second arc-sine law

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    We consider a planar Brownian motion starting from OO at time t=0t=0 and stopped at t=1t=1 and a set F={OIi;i=1,2,...,n}F= \{OI_i ; i=1,2,..., n\} of nn semi-infinite straight lines emanating from OO. Denoting by gg the last time when FF is reached by the Brownian motion, we compute the probability law of gg. In particular, we show that, for a symmetric FF and even nn values, this law can be expressed as a sum of arcsin⁥\arcsin or (arcsin⁥)2(\arcsin)^2 functions. The original result of Levy is recovered as the special case n=2n=2. A relation with the problem of reaction-diffusion of a set of three particles in one dimension is discussed

    Photovoltaic powered irrigation system applied to familiary agriculture

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    CoordenaÃÃo de AperfeÃoamento de Pessoal de NÃvel SuperiorA presente dissertaÃÃo tem como objetivo principal analisar a viabilidade tÃcnica e financeira de um sistema fotovoltaico autÃnomo para bombeamento de Ãgua aplicado na irrigaÃÃo de uma unidade de produÃÃo agrÃcola familiar. A unidade agrÃcola pesquisada està instalada no NÃcleo de Ensino e Pesquisa em Agricultura Urbana (NEPAU), que atua em parceria com o LaboratÃrio de Energias Alternativas (LEA), situados no Campus do PICI da Universidade Federal do CearÃ. A unidade ocupa uma Ãrea Ãtil de 43 m2, com um reservatÃrio de Ãgua que simula um aÃude, lago ou poÃo com capacidade de 3.534 litros, um motor bomba de 12 VDC e um mÃdulo fotovoltaico de 135 Wp. O sistema de irrigaÃÃo à constituÃdo por 12 micro-aspersores com pressÃo de trabalho de 7 psi, com raio de alcance de 1,2 m e vazÃo de 0,6 l/min. A unidade de produÃÃo consumiu 31.592 litros de Ãgua e demandou 5,2 kWh de energia elÃtrica ao longo de 44 dias de produÃÃo do coentro. Um sensor de umidade do solo foi utilizado para controlar a umidade do solo o que permitiu economizar 3.608 litros de Ãgua e 0,6 kWh de energia elÃtrica na produÃÃo de 23 kg de coentro. O custo de implantaÃÃo do sistema fotovoltaico de bombeamento desenvolvido foi de R1.694,00.AseficiA~nciasdomA~dulofotovoltaico,conjuntomotobombaeglobalforamde8,4 1.694,00. As eficiÃncias do mÃdulo fotovoltaico, conjunto motobomba e global foram de 8,4%, 42% e 3,5%, respetivamente. O tempo de retorno do capital investido à de 10 anos sem considerar nenhum subsÃdio e de 8,4 anos para um subsÃdio de 20% sobre o capital investido na aquisiÃÃo dos equipamentos.This thesis aims to analyze the technical and financial feasibility of a stand-alone photovoltaic system for irrigation applied to familiar unit production. The agricultural unit was installed in the Center for Teaching and Research in Urban Agriculture (NEPAU), which operates in partnership with the Alternative Energy Laboratory (LEA), located at the PICI campus of the Federal University of CearÃ. The unit occupies a floor area of 43 m2, with a reservoir of water that simulates a pond, lake or well with capacity of 3534 liters, a pump motor of 12 VDC and a photovoltaic module of 135 Wp. The irrigation system is composed of 12 micro-sprinklers with 7 psi working pressure, with a range of 1.2 m radius and output of 0.6 l/min. The production plant consumed 31,592 liters of water and demanded 5.2 kWh of electrical energy throughout 44 days of production of coriander. A soil moisture sensor was used to control soil moisture allowing save 3608 liters of water and 0.6 kWh of electricity in the production of 23 kg of coriander. The costs for the photovoltaic pumping system was R 1,694.00. The efficiencies of photovoltaic module, pump and global set were 8.4%, 42% and 3.5%, respectively. The return on capital invested time is 10 years without regard to any allowance and 8.4 years for a 20% allowance on capital invested in the acquisition of equipment
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