MCMC, likelihood estimation and identifiability problems in DLM models

In this article we deal with the identification problem within the Dynamic Linear Models family and show that using Bayesian estimation procedures we can deal better with these problems in comparison with the traditional Maximum Likelihood estimation approach. Using a Bayesian approach supported by Markov chain Monte Carlo techniques, we obtain the same results as the Maximum likelihood approach in the case of identifiable models, but in the case of non-identifiable models, we were able to estimate the parameters that are identifiable, as well as to pinpoint the troublesome parameters. Assuming a Bayesian approach, we also discuss the computational aspects, namely the ongoing discussion between single- versus multi-move samplers. Our aim is to give a clear example of the benefits of adopting a Bayesian approach to the estimation of high dimensional statistical models.Bayesian Statistics, DLM Models, Markov chain Monte Carlo, Maximum Likelihood, Model Identification.

Public Tertiary Education Expenditure in Portugal: a Non-Parametric Efficiency Analysis

We employ a non-parametric methodology, Data Envelopment Analysis, to estimate efficiency scores for Portuguese public universities for 2001. Due to the tertiary education organisational features we consider universities as well as faculties and institutes as decision entities. Using frontier analysis we are able to separate universities/faculties/institutes that might qualify, as “performing well” from those were some improvement might increase its efficiency. This is a first effort of checking efficiency and productivity in Portuguese public tertiary education using nonparametric analysis.expenditure in tertiary education; efficiency; production possibility frontier; DEA.

Second Order Filter Distribution Approximations for Financial Time Series with Extreme Outliers

Particle Filters are now regularly used to obtain the filter distributions associated with state space financial time series. Most commonly used nowadays is the auxiliary particle filter method in conjunction with a first order Taylor expansion of the log-likelihood. We argue in this paper that for series such as stock returns, which exhibit fairly frequent and extreme outliers, filters based on this first order approximation can easily break down. However, an auxiliary particle filter based on the much more rarely used second order approximation appears to perform well in these circumstances. To detach the issue of algorithm design from problems related to model misspecification and parameter estimation, we demonstrate the lack of robustness of the first order approximation and the feasibility of a specific second order approximation using simulated data.Bayesian inference, Importance sampling, Particle filter, State space model, Stochastic volatility.

Second Order Filter Distribution Approximations for Financial Time Series with Extreme Outlier

Particle Filters are now regularly used to obtain the filter distributions associated with state space financial time series. The method most commonly used nowadays is the auxiliary particle filter method in conjunction with a first order Taylor expansion of the log-likelihood. We argue in this paper that, for series such as stock return, which exhibit fairly frequent and extreme outliers, filters based on this first order approximation can easily break down. However, the auxiliary particle filter based on the much more rarely used second order approximation appears to perform well in these circumstances. We demonstrate our results with a typical stock market series.FParticle filters, Second order approximations, State space models, Stochastic volatility

PRODESIGN - Desenhadores com Qualificação em Design de Mobiliário Um projecto Leonardo da Vinci

O ISPV, por intermédio do Departamento de Engenharia de Madeiras - DEMad, encontra-se integrado, no âmbito do programa comunitário Leonardo da Vinci, no projecto "PRODESIGN - Desenhadores com Qualificação em Design de Mobiliário", que se encontra a ser desenvolvido por uma parceria transnacional que inclui as seguintes instituições, ligadas directa ou indirectamente à área do design de mobiliário

Sapo Campus: what users really think about an institutionally supported PLE

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Redesigning a Manufacturing System Based on Functional Independence: The Case of a Tree Nursery

AbstractThe engineering of manufacturing systems encompasses two main areas of development: the manufacturing process (manufacturing technologies, and flow and handling of materials), and the production management (flow of information - signals). These two areas must be designed to perform according to the expressed needs. This paper shows that the Axiomatic Design (AD) theory can be used to analyse a manufacturing system to find the origin of the lack of productivity, and, subsequently, to redesign a solution avoiding the weakness points. A case study of a tree nursery of a large wood production enterprise was used to show the application of the axiomatic design principles, particularly through analysing the design equation and including new design parameters with the independence in mind. The redesign solution based on the independence of functions promoted the simplification of the information (signals) flow, avoiding the identification of each production element, and avoiding errors, which increases the productivity and the production volume, by elimination of waste of time in production operations. The proposed solution brought results that encourage the application of AD to increment the productivity of manufacturing systems, in alternative to expensive investments

Níveis de usabilidade e satisfação em sites de bibliotecas

Tese de mestrado, Ciências da Documentação e Informação - Biblioteconomia, Universidade de Lisboa, Faculdade de Letras, 2011A informação assume um papel cada vez mais destacado na sociedade actual. Diversos factores levaram a que a informação se tornasse parte da vida de cada cidadão, seja por interesse e pesquisa pessoal, seja porque a mesma lhe é enviada ou apresentada. Neste contexto, as bibliotecas - local privilegiado como detentor dessa informação - também se adaptaram e enquadraram na nova realidade da Sociedade da Informação. A criação de websites, através dos quais são disponibilizados conteúdos informativos, será uma das formas mais destacadas. Desta forma, importa saber como interagem os utilizadores com esta nova ferramenta e se a mesma lhes é agradável e vantajosa, facilitando o acesso à informação e aos conteúdos que procuram. A análise de quais os aspectos que mais se destacam quando os utilizadores acedem e pesquisam num site de uma biblioteca, é então de enorme relevância. Considerando o utilizador como o ponto central da relação de marketing, torna-se fundamental saber qual a sua opinião para desta forma melhor criar e adaptar o site e seus conteúdos às expectativas e desejos de cada um.ABSTRACT: Information assumes an increasingly prominent role in today's world. It has become an essential part of our daily lives, whether by personal interest and research, or because it is sent or displayed to us. In this context, the libraries - a privileged place where that information can be found - have also adapted to and integrated within the new Information Society reality. The creation of websites will be one of the most important ways through which information content is made available. Thus, it is important to know how users interact with this new tool and whether it is pleasant and beneficial to them, facilitating access to information and the content they seek. The analysis of which aspects are the most relevant when the users access and search any site of a library, is of great relevance. Considering that the user is the focus of the marketing relationship, it becomes essential to know what is his opinion, so as to create and adapt the site and its content to each person’s expectations and desires

Rádio e internet: o desafio pode ser começar de novo

[Excerto] Num livro recente, sob o título As notícias – um manual do utilizador, o filósofo britânico, Alain de Botton, diz-nos que vivemos, no presente, num estado de permanente aborrecimento e confusão. “Todos nos damos conta, com frequência, de estar perante uma notícia de enorme importância que não nos desperta qualquer interesse”, diz o autor, para acrescentar que essa postura tem origem numa formatação narrativa, cada vez mais disseminada, que nos mergulha por breves instantes numa história complexa e que de seguida nos faz avançar para outra experiência semelhante