Repositório Institucional da Universidade de Aveiro
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Discrimination of water quality monitoring sites in River Vouga using a mixed-effect state space model
Get PDFThe surface water quality monitoring is an important concern of public organizations due to its relevance to the public health. Statistical methods are taken as consistent and essential tools in the monitoring procedures in order to prevent and identify environmental problems. This work presents the study case of the hydrological basin of the river Vouga, in Portugal. The main goal is discriminate the water monitoring sites using the monthly dissolved oxygen concentration dataset between January 2002 and May 2013. This is achieved through the extraction of trend and seasonal components in a linear mixed-effect state space model. The parameters estimation is performed with both maximum likelihood method and distribution-free estimators in a two-step procedure. The application of the Kalman smoother algorithm allows to obtain predictions of the structural components as trend and seasonality. The water monitoring sites are discriminated through the structural components by a hierarchical agglomerative clustering procedure. This procedure identified different homogenous groups relatively to the trend and seasonality components and some characteristics of the hydrological basin are presented in order to support the results
Variational problems of Herglotz type with time delay: DuBois-Reymond condition and Noether's first theorem
No full textWe extend the DuBois-Reymond necessary optimality condition and Noether's first theorem to variational problems of Herglotz type with time delay. Our results provide, as corollaries, the DuBois-Reymond necessary optimality condition and the first Noether theorem for variational problems with time delay recently proved in [Numer. Algebra Control Optim. 2(2012), no. 3, 619-630]. Our main result is also a generalization of the first Noether-type theorem for the generalized variational principle of Herglotz proved in [Topol. Methods Nonlinear Anal. 20(2002), no. 2, 261-273]
Solving Abel integral equations of first kind via fractional calculus
No full textWe give a new method for numerically solving Abel integral equations of first kind. An estimation for the error is obtained. The method is based on approximations of fractional integrals and Caputo derivatives. Using trapezoidal rule and Computer Algebra System Maple, the exact and approximation values of three Abel integral equations are found, illustrating the effectiveness of the proposed approach
Maths in-service Teacher Training and the Restructuring of Secondary Education in East-Timor
Get PDFEast Timor is undergoing a profound restructuring of its secondary education. For its success, it is crucial that foreign entities maintain their support regarding in-service training of secondary school teachers. In this context, we defined the following research questions: Under which conditions is in-service teacher training in Mathematics (Maths from this point onwards) being implemented in East Timor? How is it being done, mainly regarding the curricular materials produced - curriculum, syllabus, textbooks and teacher's guides? What are the trainer's representations of the secondary educational context and of the teachers’ pedagogical practices? We opted for a qualitative case study framed within a constructivist paradigm. Regarding the technique of data collection, we chose the inquiry through a semi-structured interview, informal conversations and the direct observation of training sessions, which were audio recorded. Data collected were submitted to content analysis, which was guided by categories that emerged from the research questions and objectives. As main results, we highlight that resources, beyond those produced in the scope of international cooperation, are still very scarce. The training course is mainly focused on the resolution of the tasks proposed in textbooks, though curricular, didactical and mathematical aspects are also discussed. The pedagogical practices of Timorese teachers are still based on a very traditional paradigm, but some changes are emerging. So, we can corroborate that change is a slow process, especially with regard to the educational context. In-service teacher training can be vital to support an adequate implementation of the restructuring of secondary education. However, many other initiatives need to be developed, from a macro (educational policies) to a micro school level
How fast can a black hole rotate?
No full textKerr black holes (BHs) have their angular momentum, J, bounded by their mass, M: Jc <= GM(2). There are, however, known BH solutions violating this Kerr bound. We propose a very simple universal bound on the rotation, rather than on the angular momentum, of four-dimensional, stationary and axisymmetric, asymptotically flat BHs, given in terms of an appropriately defined horizon linear velocity, v(H). The v(H) bound is simply that v(H) cannot exceed the velocity of light. We verify the v(H) bound for known BH solutions, including some that violate the Kerr bound, and conjecture that only extremal Kerr BHs saturate the v(H) bound
A simple and effective evolutionary algorithm for the capacitated location-routing problem
No full textThis paper proposes a hybrid genetic algorithm (GA) to solve the capacitated location-routing problem. The proposed algorithm follows the standard GA framework using local search procedures in the mutation phase. Computational evaluation was carried out on three sets of benchmark instances from the literature. Results show that, although relatively simple, the proposed algorithm is effective, providing competitive results for benchmark instances within reasonable computing time
The existence of solutions to variational problems of slow growth
No full textWe consider the existence of solutions, in the space W^{1,1}(Ω), to the problem
minimize ∫_{Ω}L(∇v(x))dx on φ+W₀^{1,1}(Ω)
where L is of slow (linear or at most quadratic) growth. We present a necessary and sufficient condition in order that, for any smooth boundary datum φ and for any bounded Ω with smooth boundary, the minimum problem be solvable
The role of public libraries in promoting reading within the family
No full textThe aim of this paper is to demonstrate some examples of good practice carried out in public libraries and their role in promoting reading within the family and in particular with parents and children. In this case, the family takes on the responsibility of bringing the book into the life of the child almost from the time they are born. Some libraries hold events which aim to bring parents and children, books and reading and ludic activities together and thus stimulate early interest in reading on the part of the child. These activities work on various levels, with a view to training parents on how to take full advantage of books, to make them more aware of the benefits of reading and how to make a good selection of reading material in order to strengthen family bonds and promote a healthier and more balanced upbringing for the child
The Moodle platform: a study in a higher education portuguese institution
No full textThis chapter analyzes Learning Management Systems (LMSs) and their main features and compares the
most popular LMSs platforms considering their utilization and the services they offer. Additionally, it
presents a study carried out at the University of Aveiro (UA) that analyses the functionalities and tools
of the Moodle platform and their use by students. The data was collected based on content analysis, one
non-structured interview with the responsible of the Moodle from the UA and a questionnaire applied to
278 students. The results show that the most mentioned purposes of the Moodle@UA were ‘Download
materials’, ‘News’ and ‘Deliver assignments’ and that the most used information materials are ‘Texts’
and ‘Slides’, showing that despite Moodle has a great potential, it is mainly used as a repository of materials.
The results also highlighted the existence of two groups of students distinguished by the degree
of importance given to the Moodle tools
Photochemical and biophysical feedbacks of C3 and C4 Mediterranean halophytes to atmospheric CO2 enrichment confirmed by their stable isotope signatures
No full textAccording the latest predictions, an increase of about two times in atmospheric CO2 concentrations, is expected to occur by the end of this century. In order to understand the effects of this atmospheric composition changes on two abundant Mediterranean halophytes (Halimione portulacoides and Spartina maritima), mesocosmos trials were performed simulating two atmospheric CO2 environments (380ppm and 760ppm of CO2 respectively). The two chosen halophyte species present different metabolic characteristics: H. portulacoides, is a C3 specie while S. maritima is a C4 species. Distinct feedbacks were obtained for each of the studied species. Stable Isotope discrimination showed that both species showed an enhancement of the Rubisco carboxylation capacity and photosynthetic efficiency mostly due to an increase in intracellular [CO2]. In H.portulacoides CO2 fertilization induced an enhancement of ETR and a decrease in non-photochemical quenching and in dissipated energy fluxes. On the other hand the C4 grass S.maritima, already at full capacity, showed no photosynthetic enhancement. In fact this highly productive grass presented lower photosynthetic efficiencies accompanied by increases in dissipated energy fluxes mostly due to reductions in energy flux associated with the transport of reducing power throughout the quinone pool. The accumulation of reducing power led to oxidative stress, and thus the photosynthetic ability of this grass was greatly reduced. Both these feedbacks to realistic future CO2 concentrations are important consideration for in future primary productivity models, indicating a possible reduced abundance of the pioneer S.maritima and an increased biomass spreading of the sediment stabilizer H.portulacoides, inevitably affecting the morphology and function of the salt marshes imposed by these atmospheric changes, both in terms of ecosystem functioning and loss of biodiversity