75 research outputs found

    Some Aspects of Latent Structure Analysis

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    Latent structure models involve real, potentially observable variables and latent, unobservable variables. The framework includes various particular types of model, such as factor analysis, latent class analysis, latent trait analysis, latent profile models, mixtures of factor analysers, state-space models and others. The simplest scenario, of a single discrete latent variable, includes finite mixture models, hidden Markov chain models and hidden Markov random field models. The paper gives a brief tutorial of the application of maximum likelihood and Bayesian approaches to the estimation of parameters within these models, emphasising especially the fact that computational complexity varies greatly among the different scenarios. In the case of a single discrete latent variable, the issue of assessing its cardinality is discussed. Techniques such as the EM algorithm, Markov chain Monte Carlo methods and variational approximations are mentioned

    Vegetative development, fruits yield and optimization of pineapple cv. Pérola with different levels of irrigation

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    Apesar de ser uma planta com necessidades hídricas relativamente baixas, o abacaxizeiro tem demanda permanente de água, variável ao longo do ciclo e dependente do seu estádio de desenvolvimento. Assim, objetivou-se analisar volumes de irrigação no desenvolvimento vegetativo, no rendimento da fruta e na otimização do abacaxizeiro cv. Pérola. O experimento foi realizado na Universidade Federal de Sergipe, município de São Cristóvão (11°01'S, 37°12'W), no delineamento em blocos ao acaso, com quatro tratamentos (lâminas de água) (100% da evaporação do tanque Classe A (523,7mm ano-1); 75% da evaporação do tanque Classe A (392,8mm ano-1), 50% da evaporação do tanque Classe A (261,8mm ano-1) e 0% da evaporação do tanque Classe A, seis repetições e 12 plantas úteis por parcela. O sistema de irrigação foi por aspersão convencional disposto em linha, com pressão de 20mca e vazão de 1,33m3 h-1. A área foliar (cm2) mínima atingida de 4552,6cm2 foi observada no volume de água de 122,9mm ano-1, enquanto a massa seca das folhas (147,6g) foi constatada com 17mm ano-1. O máximo comprimento da folha D (88,9cm) foi estimado com 532,7 mm ano-1. Já o máximo comprimento do fruto (23cm) foi observado na lâmina de 296,9mm ano-1. A massa do fruto máxima estimado de 1.736g foi constatado na lâmina de 356,4mm ano-1. No contexto, a irrigação contribui de forma positiva no desenvolvimento vegetativo e rendimento da fruta do abacaxizeiro. Ressalta-se remuneração mensal líquida de R 1.161,17ha-1, quando se adota lâmina de irrigação de 356,4mm ano-1. _________________________________________________________________________________________ ABSTRACT: Regardless a relatively low water needs, pineapple fruit has a variable behavior related to water need throughout its biological cycle depending on the development stage. The objective of this work was to analyze irrigation on the vegetative development and fruits yield in pineapple cv. Pérola. The experiment was conducted at the Universidade Federal de Sergipe Experimental Station, at São Cristóvão - SE (11°01'S, 37°12'W), in a randomized block design, with four water level treatments as follow: 100% of Class-A (523.7mm ano-1) evaporation pan; 75% of Class-A (392.8mm ano-1) evaporation pan, 50% of Class-A (261.8mm ano-1) evaporation pan and 0% of Class-A evaporation pan, in six replications and twelve plants per plot. The splinkler watering system of irrigation was installed in a line, with an operating pression of 20 mca and a sprinkler dischrage of 1.33m3h-1. A minimum leaf area of 4552.6cm2 was observed, considering a water level of 122.9mm year-1, while a leaf dry matter was 147.6 g in 17mmyear-1. The maximum leaf length (D) of 88.9cm was estimated considering 532.7mmyear-1. The maximum fruit length of 23cm was observed, considering a water level of 296.9mmyear-1. The maximum estimated fruit weight was 1.736g in a water level of 356.4mm year-1. The irrigation seems to contribute in a positive way to the vegetative development in the pineapple fruit yield. It is important to mention that it could be observed a net profit of R 1,161.17 ha-1, when a water level of 356.4mm ano-1 of irrigation was adopted
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