Time-varying Markov models of school enrolment

This study uses Markov models to develop a general quantitative approach to aid the modelling of school enrolment. The performance of the stationary 1970s to limitations Markov project of the chain model, widely used during the 1960s and school enrolment, has thrown into relief traditional model. Only a few studies early the have thoroughly tested the model over a period of time to determine whether it is really valid for predictive purposes. The present study starts by testing the stationary Markov model using data over a twelve year period for a subsystem of the Portuguese educational system, the model being applied to the whole country and to each district into which the country is administratively divided. Several least squares estimation procedures are performed to produce estimates of the transition probabilities. As expected this model proves to be inappropriate, generating biased and non-efficient estimates for the transition probabilities. Assuming that the non-stationarity of the transition probabilities is due to causal factors, linear behavioural relationships are included in the model. An extended Markov model with time varying transition probabilities is developed and applied to the same Portuguese educational subsystem. Seventeen explanatory variables, divided into supply-side factors and demand-side factors, are used, and stepwise regression and pooled cross-section time-series regression are performed to produce estimates of the time-varying transition probabilities principal components analysis is also applied on supply factors and demand factors and new sets of explanatory variables are used. The results show that the patterns of the time-varying transition probability estimates describe reasonably well the patterns of the corresponding observed point estimates. This suggests that it is appropriate to include a causal structure in the model. Having established the causal relationship influencing the time-varying transition probabilities, an analysis of these relationships suggests both policy implications of this work and areas for future research

Biofilm formation by Pseudomonas fluorescens

The formation of biofilms on heat exchange surfaces was studied using water contaminated with Pseudomonas fluorescens. The rate of deposition and the maximum amount of deposit decrease as the fluid velocity increases. The processes occurring at the interface and in the biofilm appear to govern the build-up of the deposit. together with the removal (shear stress) mechanism. Values of the attachment and biological growth rates were calculated from the changes observed in the biofilm thermal resistances after suppressing the addition of nutrients to the flowing water. In both cases there is a decrease for higher velocities.JNICT. Portugal. through Project no. 8750

Biofouling in tubes: some trends and perspectives

A significant increase in the literature concerning the formation of biological deposits in tubes has been noticed in the last few years. Yet, the scope of the majority of the reports is limited to the study of a single operating parameter. Besides, the operating conditions differ significantly from case to case, renderino difficult the absortion of the available information. In this work, a survey of the most recent publications on the subject of tube biofouling is undertaken, as a means of clarifying further research proprams. Emphasis is placed on the systems used, experimental equipments adopted and, essentially on the parameters studied. Of these, specially attention is qiven to the influence of tube material and roughness, foulant type and concentration, fluid velocity and temperature field

O estudo da alimentação desencadeador de novas práticas na História e Geografia de Portugal

Relatório de atividade profissional de mestrado em HistóriaO estudo da alimentação aplicado em dois subdomínios “Portugal nos séculos XIII e XIV” e “Portugal nos séculos XV e XVI” surge como um novo olhar na disciplina de História e Geografia de Portugal. Através de um conjunto de novas práticas, estas, inúmeras vezes articuladas com as diferentes disciplinas que compõem a matriz curricular do segundo ciclo, o aluno beneficiará de um conhecimento integrador, desenvolvendo competências diversificadas e que lhe permitirá experienciar o passado longínquo através do presente e o presente através da consciência de um tempo já ocorrido, promovendo o estabelecimento de relações transversais na História. Agindo, no palco das reconstituições, através de várias propostas subordinadas ao tema da alimentação, o professor estabelecerá, portanto, pontos de ligação com as questões económicas, sociais, culturais, religiosas, do espaço-tempo em estudo. O aluno será surpreendido, envolvendo-se, criando e descobrindo … na História e Geografia de Portugal.Food study is submitted to a consideration under two chronological sub-domains "Portugal in the 13th and 14th centuries" and "Portugal in the 15th and 16th centuries." This area emerges as a completely new area of the History and Geography of Portugal. Under a set of new approaches, articulated with the different subjects that constitute the core curriculum of the second cycle of basic education, students will benefit from an integrative knowledge, developing diversified skills that will allow the experience of the distant past by means of the present and the present through the consciousness of a time already past. Acting on the stage of reconstructions, through various proposals subordinated to the food theme, the teacher will therefore establish connection points with the economic, social, cultural, religious, space and time under study. In this way, the development of transversal relationships in history will be promoted. The student will be surprised, engaged, creating and discovering the History and Geography of Portugal

A model for the interpretation of biofouling

The formation of biofilms on heat exchange surfaces was studied using water with Pseudomonas fluorescens as a contaminant and also a mixture of these bacteria and kaolin particles. In every case increasing the fluid velocity resulted in a decrease in the final amount of deposit and in the deposition rate . The effect of the fluid velocity was interpreted using a mathematical model and it was found that cell adhesion and reproduction were the fundamental processes controlling the deposition rate . The presence of inorganic particles in the deposit enhanced the biofilm growth rate . This result was explained by the differences in the structure of the fouling layers

In-between identities and hope in the future: experiences and trajectories of cigano secondary students (SI)

Increasing numbers of Cigano people in Portuguese schools show that this is the most educated generation to date. However, according to recent data only 2.6% are enrolled in secondary education. Using an intersectional approach examining gender, ethnicity, and family socioeconomic status to explore the youngsters’ academic trajectories, and focusing on tensions of the interplay between structural constraints and individual agency, enables us to explore identity reconfiguration processes (‘in- between’). The data, based on 32 semi-structured interviews, point to three main dimensions regarding the youngsters’ aspirations for social mobility: the school relevance to achieve jobs differing from traditional activities; school perceived as a means to develop important transversal skills, useful in broader citizenship contexts; school as a privileged space for inter-ethnic socialisation, with impact on the youngsters’ school and professional future. Participant heterogeneity explains variations in their aspirations for upward mobility, as well as differentiations in the construction processes of in-between identities.This project is funded by the Foundation for Science and Technology, [PTDC/CED-EDG/30175/ 2017].info:eu-repo/semantics/publishedVersio

Surface interactions and deposit growth in fouling of heat exchangers

Fouling of heat exchangers is a costly problem in industJ)'. There is a need for a better understanding of the phenomena involved in the build up of deposits on surfaces. The paper reviews the basic mechanisms of fouling, emphasizing their rdle in determining the overall fouling rate. Mass transfer, adhesion, chemical or biological reactions can be the rate limiting processes depending on the design and operating conditions of the heat exchanger. Reference is made to the most common types of fouling, particularly in water systems, and to their interaction with corrosion of metallic surfaces. Special attention is devoted to adhesion, since the formation of fouling layers is primarily a surface process. The main forces of adhesion and the methods fa predicting adhesion tendencies are reviewed. The paper presents and discusses data obtained in laboratory studies on fouling caused by inorganic particles, by microorganisms, and also by both of these types of foulants acting simultaneously. Synergistic phenomena (positive and negative) seem to occur when two oc more types of foulants are present in the fluid, but the final result is still unpredictable. Data on the effects of fluid velocity, temperature and surface material are also presented and discussed.(undefined

Interaction between different fouling agents in water systems

Publicado em "Heat transfer 1990 : proceedings of the Ninth International Heat Transfer Conference", Jerusalem, Israel, Vol. 5 (1990)Most of the fouling studies have been up to now focused on the build up of deposits caused by only one foulant. Although this type of research allows a more clear identification of the mechanisms involved in the formation of deposits, the study of more realistic situations is now needed. The paper reports the results of fouling tests where different fouling agents were present in water: kaolin plus magnetite particles, and bacteria (Pseudomonas jl.uorescens) plus kaolin particles. Deposit formation was monitored through heat transfer measurements. The tests were performed with water flowing at several velocities and the data were compared with previous results obtained using a single foulant. in an attempt to determine possible changes in the processes controlling the fouling rate. Increased fouling resistances and rates were observed when kaolin particles were suspended in the bacteria - - water system. The kaolin - magnetite interaction seems to decrease the final amount of deposit and, at the same time, to increase its mechanical strength. Modifications in the metabolic processes or in the adhesion forces may account for the observed changes