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- An exact composite lower bound strategy for the resource-constrained project scheduling problemPublication . Coelho, José; Vanhoucke, MarioThis paper reports on results for the well-known resource-constrained project scheduling problem. A branch-and-bound procedure is developed that takes into account all best performing components from literature, varying branching schemes and search strategies, using the best performing dominance rules and assembling these components into a unified search algorithm. A composite lower bound strategy that statically and dynamically selects the best performing bounds from literature is used to find optimal solutions within reasonable times. An extensive computational experiment is set up to determine the best combination of the various components used in the procedure, in order to benchmark the current existing knowledge on four different datasets from the literature. By varying the network topology, resource scarceness and the size of the projects, the computational experiments are carried out on a diverse set of projects. The procedure was able to find some new lower bounds and optimal solutions for the PSPLIB instances. Moreover, new best known results are reported for other, more diverse datasets that can be used in future research studies. The experiments revealed that even project instances with 30 activities cannot be solved to optimality when the topological structure is varied.
- Assessing a b-learning teaching approach and students' learning preferences in higher educationPublication . Cardoso, Teresa Margarida Loureiro; Pestana, Filomena; Pina, João Aragão eDistance learning has been gaining ground in higher education institutions, particularly in the context of blended learning, forcing institutions and teachers to confront new challenges in the teaching / learning process [1] [2] [3] [4]. This trend has been increasing in the world [5] [6], namely in the United States [1] [7] and in Europe [8] [9] [6] [10]. Blended learning, or simply b-learning, has been associated with the reduction of costs and efficiency [11] [3]. According to several authors, it enables to combine face-to-face and online distance modalities (elearning or mlearning), so it is said to be the better of both worlds [12] [13] [14]. It also allows to enhance greater space-time flexibility, and when properly implemented allows the acquisition of meaningful learning, centered on student autonomy, which, among other aspects, takes into account different learning styles/preferences. Therefore, blended-learning can inspire course curriculum design, including updating former face-toface pedagogical offers in order to meet the blended or hybrid principles and delivery. Bearing in mind this teaching / learning specific scenario, we developed two surveys to assess such a new teaching approach and the students’ preferences, in two different moments – at the beginning and at the end of a higher education unit course. Hence, in this text, we will present those surveys, as well as their theoretical and methodological framework. Both surveys have already been validated and tested, and preliminary data analysis is being developed. We expect this pedagogical approach can contribute to sustain the assessment of teaching practices towards students’ learning preferences, and the choice of adequate technologies to fit those preferences. Ultimately, we expect the results can shed light for further research, so as to improve the development of blended-learning course curriculum design in higher education.
- Dynamics of a differential system using invariant regionsPublication . Costa, Fernando Pestana daThe longtime behaviour of a two dimensional system of ordinary differential equations with singularities is studied using conveniently defined positively invariant sets and auxiliary functions. The approach uses only elementary techniques of phase plane analysis and provides a good geometric insight into the dynamical behaviour of the system. It provides dynamical information analogous to what is usually obtained via centre manifold techniques but does not require the flow to be defined at the limit point.
- A hierarchical cluster system based on Horton-Strahler rules for river networksPublication . Costa, Fernando Pestana da; Grinfeld, Michael; Wattis, Jonathan ADWe consider a cluster system in which each cluster is characterized by two parameters: an \order" i; following Horton-Strahler's rules, and a \mass" j following the usual additive rule. Denoting by ci;j (t) the concen- tration of clusters of order i and mass j at time t; we derive a coagulation- like ordinary di erential system for the time dynamics of these clusters. Results about existence and the behaviour of solutions as t ! 1 are ob- tained, in particular we prove that ci;j (t) ! 0 and Ni(c(t)) ! 0 as t ! 1; where the functional Ni( ) measures the total amount of clusters of a given xed order i: Exact and approximate equations for the time evolution of these functionals are derived. We also present numerical results that sug- gest the existence of self-similar solutions to these approximate equations and discuss its possible relevance for an interpretation of Horton's law of river numbers
- Recursos Educacionais Abertos nos Repositórios RCAAP: panorama atualPublication . Carvalho, Madalena; Bastos, GlóriaO trabalho tem como objetivo preencher uma lacuna relativa à identificação do modo como a temática dos Recursos Educacionais Abertos (REA) é apresentada nos repositórios institucionais portugueses representados no Diretório RCAAP - Repositórios Científicos de Acesso Aberto de Portugal. A investigação teve por base uma pesquisa exploratória-descritiva com abordagem quantitativa e qualitativa de modo a retratar os cenários evidenciados pelos repositórios portugueses. A recolha da informação foi efetuada em março de 2023 e a fonte de recolha de dados foi o Diretório RCAAP. Partindo dos referenciais teóricos sobre a temática, nomeadamente as recomendações da UNESCO, foi efetuada uma análise aos repositórios referenciados no Diretório RCAAP que permitiu: 1 - Identificar os repositórios com documentos classificados como “Recurso Educacional” 2 - Percecionar a diversidade de abordagens e de critérios relativas ao licenciamento, à organização e à disponibilização do acesso aos conteúdos. 3 - Avaliar o nível de compromisso dos repositórios portugueses para com o cumprimento das diretrizes definidas pela UNESCO para os Recursos Educacionais Abertos.
- Tabulation for multi-purpose partial parsingPublication . Rocio, Vitor; Lopes, Gabriel; Clergerie, EricEfficient partial parsing systems (chunkers) are urgently required by various natural language application areas as these parsers always produce partially parsed text even when the text does not fully fit existing lexica and grammars. Availability of partially parsed corpora is absolutely necessary for extracting various kinds of information that may then be fed into those systems, increasing their processing power. In this paper, we propose an efficient partial parsing scheme based on chart parsing that is flexible enough to support both normal parsing tasks and diagnosis in previously obtained partial parses of possible causes (kinds of faults) that led to those partial parses instead of complete parses. Through the use of the built-in tabulation capabilites of the DyALog system, we implemented a partial parser that runs as fast as the best non-deterministic parsers. In this paper we ellaborate on the implementation of two different grammar formalisms: Definite Clause Grammars (DCG) extended with head declarations and Bound Movement Grammars (BMG).
- A tool to test and validate algorithms for the resource-constrained project scheduling problemPublication . Vanhoucke, Mario; Coelho, JoséIn a paper written by by Vanhoucke et al. (2016), an overview of artificial and empirical project databases has been given for integrated project management and control. These databases are collections of the most well-known and widespread data instances available in literature for the construction of a baseline schedule, the analysis of schedule risk or the use for project control. The current paper serves as a follow-up study to further elaborate on the use of these data instances, and to give researchers an incentive to use these datasets for their research on the development and validation of new algorithms for project scheduling. Therefore, unlike the general focus of the previous paper on baseline scheduling, schedule risk analysis and project control, the focus on the current paper is restricted to resource-constrained project scheduling. The intention of this follow-up overview is fourfold. First and foremost, a procedure is proposed to facilitate the reporting of best known solutions for the well-known single- and multi-mode resource-constrained project scheduling problem to minimize the project makespan. Secondly, the paper reports our best known solutions we obtained so far, and reflects on the network and resource parameters that increase the project complexity. In doing so, areas to focus on for future research are detected, and an attempt to define hard problem instances is given. Thirdly, a new dataset is presented for the resource-constrained project scheduling problem that is much more diverse in both the network topology and resource scarceness and will enable the future researcher to develop algorithms to solve a wider range of project problems. Finally, the paper also adds some links to tutorials and other relevant information to stimulate researchers to download the data and update best known solutions once available.
- A well conditioned method of fundamental solutions for laplace equationPublication . Antunes, Pedro R. S.The method of fundamental solutions (MFS) is a numerical method for solving boundary value problems involving linear partial differential equations. It is well known that it can be very effective assuming regularity of the domain and boundary conditions. The main drawback of the MFS is that the matrices involved typically are ill-conditioned and this may prevent to achieve high accuracy. In this work, we propose a new algorithm to remove the ill conditioning of the classical MFS in the context of Laplace equation defined in planar domains. The main idea is to expand the MFS basis functions in terms of harmonic polynomials. Then, using the singular value decomposition and Arnoldi orthogonalization we define well conditioned basis functions spanning the same functional space as the MFS's. Several numerical examples show that this approach is much superior to previous approaches, such as the classical MFS or the MFS-QR.