Browsing by Author "Costa e Silva, Eliana"
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- Guidelines for Creating Video Podcasts in Mathematics Higher Education.Publication . Costa, Sidonie; Costa e Silva, Eliana; Correia, Aldinab-Mat@plicada is a b-learning Mathematics course for Higher Education students, mainly composed of educational videos available in the institutional Moodle platform. These contents were created by following a set of guidelines, where three components are considered: the quality of students’ learning, the teacher’s time and computer skills, as well as the equipment made available by the institution. With the aim of evaluating the procedure used to make these videos, an experiment was carried out in classroom context, using a video on matrix multiplication which is included in the course syllabus. After its visualization, the 49 students who participated in the experiment completed a questionnaire assessing viewing behaviour, perception, attitudes, satisfaction, and learning performance. The findings demonstrate the importance of using video podcasts in Higher Education as complementary tools and the adequacy of the selected b-Mat@plicada video. Also, the results indicate that, from the students’ perspective, the speech, sound, and image are the most important features in a video podcast.
- A Human-like Upper-limb Motion Planner: Generating naturalistic movements for humanoid robotsPublication . Gulletta, Gianpaolo; Costa e Silva, Eliana; Erlhagen, Wolfram; Meulenbroek, Ruud; Costa, Maria Fernanda Pires; Bicho, EstelaAs robots are starting to become part of our daily lives, they must be able to cooperate in a natural and efficient manner with humans to be socially accepted. Human-like morphology and motion are often considered key features for intuitive human–robot interactions because they allow human peers to easily predict the final intention of a robotic movement. Here, we present a novel motion planning algorithm, the Human-like Upper-limb Motion Planner, for the upper limb of anthropomorphic robots, that generates collision-free trajectories with human-like characteristics. Mainly inspired from established theories of human motor control, the planning process takes into account a task-dependent hierarchy of spatial and postural constraints modelled as cost functions. For experimental validation, we generate arm-hand trajectories in a series of tasks including simple point-to-point reaching movements and sequential object-manipulation paradigms. Being a major contribution to the current literature, specific focus is on the kinematics of naturalistic arm movements during the avoidance of obstacles. To evaluate human-likeness, we observe kinematic regularities and adopt smoothness measures that are applied in human motor control studies to distinguish between well-coordinated and impaired movements. The results of this study show that the proposed algorithm is capable of planning arm-hand movements with human-like kinematic features at a computational cost that allows fluent and efficient human–robot interactions.
- Inventory models with reverse logistics for assets acquisition in a liquefied petroleum gas companyPublication . Lopes, Cristina; Correia, Aldina; Costa e Silva, Eliana; Monteiro, Magda; Borges Lopes, RuiThis paper addresses a case study regarding inventory models for acquiring liquefied petroleum gas (LPG) cylinders. This is an industrial challenge that was proposed at an European Study Group with Industry, by a Portuguese energy company, for which the LPG cylinder is the main asset of its LPG business. Due to the importance of this asset, an acquisition plan must be defined in order to determine the amount of LPG cylinders to acquire, and when to acquire them, in order to optimize the investment. As cylinders are returned and refilled, the reverse logistic flows of these assets must be considered. As the classical inventory models are not suitable for this case study, three new inventory models, which account for the return of LPG cylinders, are proposed in this work. The first proposed model considers deterministic constant demand and continuous returns of LPG cylinders, with discrete replenishment from the supplier. The second model is similar, but for the case when the returnedcylinders cover for the demand. A third model is also proposed considering that boththe demand and the returns are stochastic in nature and the replenishment from thesupplier is discrete. The three models address different scenarios that the company iseither currently facing or is expecting to occur in the near future.
- A Mathematical Model for Supermarket Order PickingPublication . Costa e Silva, Eliana; Cruz, Manuel; Lopes, Isabel Cristina; Moura, AnaOrder picking consists in retrieving products from storage locations to sat- isfy independent orders from multiple customers. It is generally recognized as one of the most significant activities in a warehouse (Koster et al, 2007). In fact, order picking accounts up to 50% (Frazelle, 2001) or even 80% (Van den Berg, 1999) of the total warehouse operating costs. The critical issue in today’s business environ- ment is to simultaneously reduce the cost and increase the speed of order picking. In this paper, we address the order picking process in one of the Portuguese largest companies in the grocery business. This problem was proposed at the 92nd European Study Group with Industry (ESGI92). In this setting, each operator steers a trolley on the shop floor in order to select items for multiple customers. The objective is to improve their grocery e-commerce and bring it up to the level of the best inter- national practices. In particular, the company wants to improve the routing tasks in order to decrease distances. For this purpose, a mathematical model for a faster open shop picking was developed. In this paper, we describe the problem, our proposed solution as well as some preliminary results and conclusions.
- A mixed integer nonlinear multiperiod model for supply chain management of a company in the retail sectorPublication . Teixeira, Ana; Costa e Silva, Eliana; Lopes, Isabel CristinaThe fluctuations in the business environment and seasonal variations characteristic of food supply chains contribute greatly to the increasing complexity of the entire Supply Chain planning. In the present paper, quantitative models are applied to support the decision-making purchasing management department of a retail company. Specifically, a multiperiod mathematical model was developed with the aim of optimizing decision-making of the purchasing managers. The developed model consists of a multiperiod Mixed Integer Nonlinear Programming model, with the objective to minimize the ratio between how much is costing the company to move the products along the Supply Chain and the products’ costs. It is discussed how to order the product, what is the most advantageous storage mode and whether it is preferable to order once or twice a week. Real instances, provided by a Portuguese retail company, regarding the demand for one year are tested for two scenarii, which are used currently by the company. The results show that the proposed model can reduce, on both scenarios, the ratio between operational costs and merchandise costs, for almost all products, and therefore it can be an important tool for supporting decision-making of the purchasing manager.
- Teaching Operational Research using Games and Simulation: a case studyPublication . Lopes, Cristina; Costa e Silva, ElianaThe use of gamification in teaching is not a novelty. It has been recognized as an effective method for fostering academic and practical skills, while simultaneously enhancing student engagement and motivation. In this work, we report on the use of web-based apps in classroom for introducing concepts and methods of Operational Research (OR) to students of Logistics and Business. Specifically, the Burrito Optimization game, available by Gurobi, and the TSP DYI app, developed by William Cook of the University of Waterloo, are employed to introduce mathematical optimization. The Burrito Optimization game simulates the facility location problem, challenging students to strategically position food trucks to optimize costs and profits, thereby acquainting them with linear programming models. Similarly, the TSP DYI app gamifies the TSP, encouraging student participation and competition while acquainting them with heuristic algorithms and optimization techniques. Through student feedback analysis, this study explores the efficacy of these gamified approaches in enhancing student engagement with OR concepts and motivating further exploration of complex topics. These web-based apps serve as entry points for aspiring data scientists and problem solvers, teaching why optimization is valuable and important, why it is difficult and why solvers and other optimization algorithms are essential.
- The Dynamics between Structural Conditions and Entrepreneurship in Europe: Feature Extraction and System GMM ApproachesPublication . Borges, Ana; Correia, Aldina; Costa e Silva, Eliana; Carvalho, GlóriaStructural conditions and population characteristics of countries have been identified in the literature as factors for an individual to become, or to have intentions of becoming, an entrepreneur. However, this is still a subject under research, which has become increasingly relevant and could be crucial in the current challenges of European countries. In this work, the factors for entrepreneurial intentions and entrepreneurship activity are studied. More precisely, the structural conditions of European countries, which has changed over the last two decades, is analysed. The aim is to describe this behaviour and to state the main conditions for developing entrepreneurship activities and the intentions to become an entrepreneur. To achieve this purpose, feature extraction, namely, principal component analysis and dynamic longitudinal approaches are used. In particular, we propose that the system-generalised method of moments (GMM) model is adequate in this situation. The results suggest that the structure of the European framework conditions for entrepreneurship, obtained using the Factor Analysis year by year, is quite diversified until 2008, while after 2008, it is more stable. Moreover, it is concluded that the conditions associated with entrepreneurial intentions and entrepreneurial activity differ between these two time periods. Hence, the dynamic aspect of the structural conditions that affect entrepreneurial activities or intentions should be acknowledged.
- Unveiling the Dynamics of the European Entrepreneurial Framework Conditions over the Last Two Decades: A Cluster AnalysisPublication . Costa e Silva, Eliana; Correia, Aldina; Borges, Ana