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Search Results: 1 - 10 of 9001 matches for " Silvia Bianconcini "
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Asymptotic properties of adaptive maximum likelihood estimators in latent variable models
Silvia Bianconcini
Statistics , 2012, DOI: 10.3150/13-BEJ531
Abstract: Latent variable models have been widely applied in different fields of research in which the constructs of interest are not directly observable, so that one or more latent variables are required to reduce the complexity of the data. In these cases, problems related to the integration of the likelihood function of the model arise since analytical solutions do not exist. In the recent literature, a numerical technique that has been extensively applied to estimate latent variable models is the adaptive Gauss-Hermite quadrature. It provides a good approximation of the integral, and it is more feasible than classical numerical techniques in presence of many latent variables and/or random effects. In this paper, we formally investigate the properties of maximum likelihood estimators based on adaptive quadratures used to perform inference in generalized linear latent variable models.
A general multivariate latent growth model with applications in student careers Data warehouses
Silvia Bianconcini,Silvia Cagnone
Statistics , 2009, DOI: 10.3102/1076998610396886
Abstract: The evaluation of the formative process in the University system has been assuming an ever increasing importance in the European countries. Within this context the analysis of student performance and capabilities plays a fundamental role. In this work we propose a multivariate latent growth model for studying the performances of a cohort of students of the University of Bologna. The model proposed is innovative since it is composed by: (1) multivariate growth models that allow to capture the different dynamics of student performance indicators over time and (2) a factor model that allows to measure the general latent student capability. The flexibility of the model proposed allows its applications in several fields such as socio-economic settings in which personal behaviours are studied by using panel data.
Estimation of latent variable models for ordinal data via fully exponential Laplace approximation
Silvia Bianconcini,Silvia Cagnone
Statistics , 2011, DOI: 10.1016/j.jmva.2012.06.005
Abstract: Latent variable models for ordinal data represent a useful tool in different fields of research in which the constructs of interest are not directly observable. In such models, problems related to the integration of the likelihood function can arise since analytical solutions do not exist. Numerical approximations, like the widely used Gauss Hermite (GH) quadrature, are generally applied to solve these problems. However, GH becomes unfeasible as the number of latent variables increases. Thus, alternative solutions have to be found. In this paper, we propose an extended version of the Laplace method for approximating the integrals, known as fully exponential Laplace approximation. It is computational feasible also in presence of many latent variables, and it is more accurate than the classical Laplace method.
A new set of asymmetric filters for tracking the short-term trend in real-time
Estela Bee Dagum,Silvia Bianconcini
Statistics , 2015, DOI: 10.1214/15-AOAS856
Abstract: For assessing in real time the short-term trend of major economic indicators, official statistical agencies generally rely on asymmetric filters that were developed by Musgrave in 1964. However, the use of the latter introduces revisions as new observations are added to the series and, from a policy-making viewpoint, they are too slow in detecting true turning points. In this paper, we use a reproducing kernel methodology to derive asymmetric filters that converge quickly and monotonically to the corresponding symmetric one. We show theoretically that proposed criteria for time-varying bandwidth selection produce real-time trend-cycle filters to be preferred to the Musgrave filters from the viewpoint of revisions and time delay to detect true turning points. We use a set of leading, coincident and lagging indicators of the US economy to illustrate the potential gains statistical agencies could have by also using our methods in their practice.
Approximate likelihood inference in generalized linear latent variable models based on integral dimension reduction
Silvia Bianconcini,Silvia Cagnone,Dimitris Rizopoulos
Statistics , 2015,
Abstract: Latent variable models represent a useful tool for the analysis of complex data when the constructs of interest are not observable. A problem related to these models is that the integrals involved in the likelihood function cannot be solved analytically. We propose a computational approach, referred to as Dimension Reduction Method (DRM), that consists of a dimension reduction of the multidimensional integral that makes the computation feasible in situations in which the quadrature based methods are not applicable. We discuss the advantages of DRM compared with other existing approximation procedures in terms of both computational feasibility of the method and asymptotic properties of the resulting estimators.
Forma??o de educadores a distancia na pós-gradua??o: potencialidades para o desenvolvimento da investiga??o e produ??o de conhecimento
Almeida, Maria Elizabeth Bianconcini de;
Educa??o & Sociedade , 2012, DOI: 10.1590/S0101-73302012000400008
Abstract: the purpose of this work is to offer evidence for distance teacher training programs in postgraduate programs based in the commitment with the investigation, the advances of scientific writings and the publication of results. this work is structured in three parts, mainly: general view of policies, regulation and structuring of distance learning in brazilian higher education; principles of interaction, reflection, investigation, collaboration and development of knowledge; indications of contributions for the development of distance education postgraduate programs
Educa??o a distancia na internet: abordagens e contribui??es dos ambientes digitais de aprendizagem
Almeida, Maria Elizabeth Bianconcini de;
Educa??o e Pesquisa , 2003, DOI: 10.1590/S1517-97022003000200010
Abstract: the advances and dissemination of the use of information and communication technology (ict) open up new perspectives for distance learning based on digital learning environments accessed through the internet. considering that geographical distance and the use of new media, although inherent features of distance learning (dl), do not suffice to define this educational conception, dl is here discussed neither as a makeshift solution to cater for students geographically isolated from educational institutions, nor just as a simple transposition of contents and methods of presence teaching to other media supported by various technologies. dl programs can have their level of dialogue prioritized or not according to the epistemological conception, support technologies and pedagogical approach. this article intends to discuss the usual approaches to dl, highlighting the use of ict in the development of an interactive education process that promotes the production of individual and group knowledge in collaborative processes favored by the use of digital and interactive learning environments, which allow to break from time and space distances and make feasible recursiveness, multiple interferences, connections and trajectories, not restricting itself to the dissemination of information and tasks entirely defined a priori.
Educa o a distancia na internet: abordagens e contribui es dos ambientes digitais de aprendizagem
Almeida Maria Elizabeth Bianconcini de
Educa??o e Pesquisa , 2003,
Abstract: Os avan os e a dissemina o do uso das tecnologias de informa o e comunica o (TIC) descortinam novas perspectivas para a educa o a distancia com suporte em ambientes digitais de aprendizagem acessados via internet. Considerando-se que a distancia geográfica e o uso de múltiplas mídias s o características inerentes à educa o a distancia, mas n o suficientes para definirem a concep o educacional, discute-se a educa o a distancia (EaD) n o como uma solu o paliativa para atender alunos situados distantes geograficamente das institui es educacionais nem apenas como a simples transposi o de conteúdos e métodos de ensino presencial para outros meios e com suporte em distintas tecnologias. Os programas de EaD podem ter o nível de diálogo priorizado ou n o segundo a concep o epistemológica, tecnologias de suporte e respectiva abordagem pedagógica. Este artigo pretende discutir as abordagens usuais da educa o a distancia, destacando o uso das TIC para o desenvolvimento de um processo educacional interativo que propicia a produ o de conhecimento individual e grupal em processos colaborativos favorecidos pelo uso de ambientes digitais e interativos de aprendizagem, os quais permitem romper com as distancias espa o-temporais e viabilizam a recursividade, múltiplas interferências, conex es e trajetórias, n o se restringindo à dissemina o de informa es e tarefas inteiramente definidas a priori.
Tecnologias na Educa o: dos caminhos trilhados aos atuais desafios Technology in Education: the paths travelled to the current challenges
Maria Elizabeth Bianconcini de Almeida
Bolema: Boletim de Educa??o Matemática , 2008,
Abstract: Este artigo apresenta um resgate da recente história das tecnologias de informa o e comunica o na educa o a partir de uma retrospectiva dos caminhos trilhados em países cujas a es tiveram forte influência na trajetória brasileira, com destaque especial para Estados Unidos da América, Fran a e Portugal. Em seguida, o tema é tratado no ambito da realidade brasileira até o momento atual caracterizado pela proposta de inserir equipamentos móveis de pequeno porte e baixo custo (laptop educacional) nas escolas. No final, destaca as principais convergências que se sobressaem na história das tecnologias na educa o desses países e conclui que, apesar da disparidade quantitativa em rela o à disponibilidade de recursos entre esses países, a concretiza o das a es se mostra aquém dos objetivos, metas, desejos e utopias, com desafios a superar, em especial no que se refere à forma o de educadores, para a efetiva integra o das TIC na escola e no currículo. Palavras-chave: Tecnologias de Informa o e Comunica o. Tecnologias na Educa o. Políticas Públicas. Integra o de Tecnologias ao Currículo. This article presents a review of the recent history of information and communication technologies in education through a retrospective of the paths traveled in countries whose actions have had strong influence on the Brazilian trajectory, with special emphasis on the United States, France and Portugal. The subject is next addressed in the context of the Brazilian reality, characterized by the current proposal to introduce small, portable, low cost equipment (educational laptops) in schools. Finally, the major convergences that stand out in the history of technology in education in these countries is highlighted. It is concluded that, despite the quantitative disparity between these countries with respect to the availability of resources, the implementation of actions has not achieved the objectives, goals, desires and utopias, and many challenges remain to be overcome, particularly with regard to the training of educators for the effective integration of ICT in schools and the curriculum. Keywords: Information and Communication Technology. Technologies in Education. Public Policy. Integration of Technologies in the Curriculum.
Influence of body mass and environmental oxygen tension on the oxygen consumption rates of an enteropneust, Glossobalanus crozieri
Ditadi, A.S.F.;Mendes, E.G.;Bianconcini, M.S.C.;
Brazilian Journal of Medical and Biological Research , 1997, DOI: 10.1590/S0100-879X1997001200010
Abstract: the present study deals with a species of enteropneust, glossobalanus crozieri, focusing on two aspects of its respiration: a) oxygen consumption and body mass, and b) the influence of environmental oxygen tension on the respiratory rate. preliminarily, the body water content was shown to be 85% of the whole body weight. the regression coefficient of the oxygen consumption on the wet body mass (0.578) seems to agree with the view that in enteropneusts respiration is mainly cutaneous. the respiratory rate was significantly reduced at o2 tensions from 76 mmhg downwards, suggesting conformity rather than regulation
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