Estimação jackknife ponderada do erro quadrático médio de predição do EBLUP temporal

A metodologia baseada na melhor predição linear empírica não enviesada (Empirical Best Linear Unbiased Prediction), consagrada com o acrónimo EBLUP, é muito utilizada na estimação de parâmetros para pequenos domínios. Apesar da relativa facilidade de dedução dos EBLUPs, mesmo num contexto de um modelo longitudinal, a medição da sua qualidade é um problema complexo devido à di culdade de estimação do erro quadrático médio de predição (EQMP) de tais preditores. Neste trabalho utiliza-se um estimador de parâmetros de interesse em pequenos domínios assistido pelo modelo temporal de Rao-Yu (Rao e Yu, 1994). O EBLUP temporal é apresentado e é revisitada a aproximação analítica assimptótica do EQMP do EBLUP temporal proposta por Rao e Yu (1994). Sob o modelo de Rao-Yu, é proposta uma metodologia jackknife ponderada para estimar o EQMP do EBLUP, desenvolvida a partir dos trabalhos de Chen e Lahiri (2008). Foi realizado um estudo por simulação com o objectivo de comparar o desempenho do estimador proposto com o obtido por via da aproximação analítica do EQMP

Estimação em Pequenos Domínios com modelos que combinam Informação Seccional e Cronológica

O objectivo principal deste artigo consiste na proposta de um novo estimador para parâmetros de interesse em pequenos domínios com dados de nível área

Modelo de simulaçâo para projecto e avaliaçâo de sistemas de rega localizada

O modelo iterativo AVALOC, em linguagem VISUAL BASIC 4.0, foi desenvolvido para o dimensionamento e a análise de funcionamento de sistemas de rega localizada (ou microrrega). O modelo apoia-se numa base de dados contendo informação relativa aos emissores e aos tubos disponíveis no comércio, e aos sectores de rega a que é aplicado o programa. A base de dados permite com relativa facilidade a introdução, a consulta e a correcção dos dados e, desta forma, reduzir o tempo de utilização do programa. No modo de dimensionamento em projecto, o programa permite seleccionar os emissores que melhor respondam aos objectivos do projecto, bem como escolher e dimensionar as condutas que constituem a rede de rega. Os cálculos são realizados segundo criterios de exclusão, i.e. obrigando a que sejam satisfeitos determinados critérios de desempenho fixados pelo utilizador, nomeadamente referentes à variação de carga e à uniformidade de emissão, visando assegurar que a distribuição de caudais no sector seja adequadamente uniforme. No modo de análise de desempenho, a simulação hidráulica visa calcular os parâmetros de funcionamento característicos do sistema, tais como o par carga - caudal de cada saída, o tempo de funcionamento, a percentagem de solo humedecido e indicadores de desempenho da rega, nomeadamente o coeficiente de uniformidade de Christiansen e a uniformidade de emissão. O modelo é apresentado utilizando um caso de projecto de um sector de rega em olival

Simulation of a milk run material transportation system in the semiconductors industry

This paper deals with a project that consisted in the implementation of a Milk Run Lot Transportation System in Qimonda Porto Test Area, done by a multidisciplinary team formed by Qimonda Porto's workers, and the development of the corresponding simulation model. The first part of the study concerns an industrial engineering assessment of the test area, which identified sources of waste and improvement possibilities, and the implementation process of a Milk Run system in this area. Secondly, the results of the system implementation are discussed, and the construction of a simulation model in Arena® is presented. The purpose of the simulation exercise is to test different system configurations that may allow the improvement of the real-world system. Finally, some information about the simulation results and further steps to be taken regarding the improvement of the system is presented. The target of the project, framed in a Lean approach, was to reduce waste, namely transportation waste, thus optimizing the utilization of the test area human resources.info:eu-repo/semantics/publishedVersio

Estimation of unemployment rates in small areas of Portugal: a best linear unbiased prediction approach versus a hierarchical Bayes approach

The high level of unemployment is one of the major problems in most European countries nowadays. Hence, the demand for small area labor market statistics has rapidly increased over the past few years. The Labour Force Survey (LFS) conducted by the Portuguese Statistical Office is the main source of official statistics on the labour market at the macro level (e.g. NUTS2 and national level). However, the LFS was not designed to produce reliable statistics at the micro level (e.g. NUTS3, municipalities or further disaggregate level) due to small sample sizes. Consequently, traditional design-based estimators are not appropriate. A solution to this problem is to consider model-based estimators that "borrow information" from related areas or past samples by using auxiliary information. This paper reviews, under the model-based approach, Best Linear Unbiased Predictors and an estimator based on the posterior predictive distribution of a Hierarchical Bayesian model. The goal of this paper is to analyze the possibility to produce accurate unemployment rate statistics at micro level from the Portuguese LFS using these kinds of stimators. This paper discusses the advantages of using each approach and the viability of its implementation

Integrated design of production systems in a lighting manufacturer using CAD and simulation in layout and process optimization

This paper discusses production systems design issues, applied to the production system layout of a manufacturer of lighting fittings and components. In this paper, production systems design software tools – Information Systems, Simulation and Computer Aided Design are integrated, exploring ways of dealing with data diversity and assuring valid and efficient production system layouts, taking advantage of the mentioned data integration. This integration is implemented on Microsoft Access (databases with system knowledge repository), AutoCAD (layout design) and WITNESS (simulation). The software package developed was called IDS (Integrated Design of Systems). This approach can help on global system optimization that considers all important system resources and system performance measures. Solutions are expected to be faster to achieve and better than solutions obtained with non-integrated approaches. IDS approach is open and accessible, thus enabling different companies to use this advanced production systems design tool, taking advantage of simulation and CAD systems and their integration. This application intends to validate the concept and functionalities of the proposed tool, on a real industrial case study.This work has been supported by FCT – Fundação para a Ciência e Tecnologia (algoritmi

Actual and standard crop coefficients for semi‑natural and planted grasslands and grasses: a review aimed at supporting water management to improve production and ecosystem services

Natural and planted grasslands play a very important role in agriculture as source of various ecosystem services, including carbon sequestration and biodiversity, and are responsible for a large fraction of agricultural water use in rainfed and irrigated fields. It is, therefore, relevant to precisely know their water use and vegetation requirements with consideration of relevant climate, from extremely cold, dry, with long winter seasons, to tropical humid and hot climates, thus with a large variability of vegetation. Semi-natural grasslands are basically used for grazing and mainly refer to highland pastures and meadows, steppes, savannas, pampas, and mixed forest systems. The FAO method to compute crop (vegetation) evapotranspiration (ETc) through the product of a crop coefficient (K c ) by the reference evapotranspiration (ETo ) is adopted. The selected papers were those where actual ETc (ETc act ) was derived from field observations and ETo was computed with the FAO56 definition, or with another method that could be referred to the former. Field derived ETc act methods included soil water balance, Bowen ratio and eddy covariance measurements, as well as remote sensing vegetation indices or surface energy balance models, thus reviewed Kc act (ETc act/ETo) values were obtained from field data. These Kc act refer to initial, mid-season and end season (K c act ini , K c act mid , K c act end ) when reported values were daily or monthly; otherwise, only average values (K c act avg ) were collected. For cases relative to cold or freezing winters, data refer to the warm season only. For grasses cut for hay, K c act ini , Kc act mid , and Kc act end refer to a cut cycle. Kc act values rarely exceeded 1.25, thus indicating that field measurements reported did respect the available energy for evaporation. Overall, K c act mid for semi-natural grasslands in cold climates were lower than those in hot climates except when available water was high, with K c act mid for meadows and mountain pastures gener- ally high. Steppes have K c act mid values lower than savannas. Grasses commonly planted for hay and for landscape generally showed high K c act mid values, while a larger variability was observed with grasses for grazing. The collected K c act values were used to define standard Kc values for all grassland and grasses. Nevertheless, the tabulated Kc act are indicative values of K c to be used for actual water management purposes and/or irrigation scheduling of planted grasslands. It is expected that a better knowledge of the standard and/or indicative K c values for a wide variety of grasslands and grasses will support better management aimed to improve grass productivity and ecosystem services, including biodiversity and carbon sequestrationinfo:eu-repo/semantics/publishedVersio