CIICESI

Eliana Silva

Integrated Researcher

[{"id":"P-00V-2A0","modifiedTime":1657141768,"title":"A Case Study on Scheduling of Repairs in an Automobile Shop","year":"2022","authors":["Pilar, MF","Silva, ECE","Borges, A"],"type":"Proceedings Paper","publicationTitle":"INNOVATIONS IN MECHANICAL ENGINEERING","abstract":"The classical combinatorial problem of scheduling is extensively studied and arises in several economic domains. However, there are few studies in the automobile sector, particularly in scheduling vehicle repair tasks and using real instances. This paper intends to contribute to fill this gap, focusing on the scheduling of the repairs of the mechanical section of a Portuguese firm in the automobile sector. A mathematical model is presented that will assist the shop manager on the scheduling of the repairs, taking into account: the mechanics and other resources that are available, the mechanical interventions to be performed on each vehicle and its expected processing time. The aim is to reduce the time of inactivity of the vehicles between interventions, as well as, the downtime of mechanics, and therefore improve productivity. The results, from real instances extracted from the data provided by the firm, show that the interventions are scheduled in a suitable form, and there is a reduction of the downtimes.","doi":"10.1007/978-3-030-79165-0_22","issn":"2195-4356","volume":"","reference":"Pilar, MF., Silva, ECE., Borges, A (2022). A Case Study on Scheduling of Repairs in an Automobile Shop. INNOVATIONS IN MECHANICAL ENGINEERING. Vol.. ISSN 2195-4356. Doi 10.1007/978-3-030-79165-0_22. "},{"id":"P-00W-C2E","modifiedTime":1678132849,"title":"The Dynamics between Structural Conditions and Entrepreneurship in Europe: Feature Extraction and System GMM Approaches","year":"2022","authors":["Borges, A","Correia, A","Silva, ECE","Carvalho, G"],"type":"Article","publicationTitle":"MATHEMATICS","abstract":"Structural 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.","doi":"10.3390/math10081349","issn":"2227-7390","reference":"Borges, A., Correia, A., Silva, ECE., Carvalho, G (2022). The Dynamics between Structural Conditions and Entrepreneurship in Europe: Feature Extraction and System GMM Approaches. MATHEMATICS. ISSN 2227-7390. Doi 10.3390/math10081349. "},{"id":"P-00T-PY2","modifiedTime":1622670680,"title":"A Hybrid Metaheuristics Parameter Tuning Approach for Scheduling through Racing and Case-Based Reasoning","year":"2021","authors":["Pereira, I","Madureira, A","Silva, ECE","Abraham, A"],"type":"Article","publicationTitle":"APPLIED SCIENCES-BASEL","abstract":"In real manufacturing environments, scheduling can be defined as the problem of effectively and efficiently assigning tasks to specific resources. Metaheuristics are often used to obtain near-optimal solutions in an efficient way. The parameter tuning of metaheuristics allows flexibility and leads to robust results, but requires careful specifications. The a priori definition of parameter values is complex, depending on the problem instances and resources. This paper implements a novel approach to the automatic specification of metaheuristic parameters, for solving the scheduling problem. This novel approach incorporates two learning techniques, namely, racing and case-based reasoning (CBR), to provide the system with the ability to learn from previous cases. In order to evaluate the contributions of the proposed approach, a computational study was performed, focusing on comparing our results previous published results. All results were validated by analyzing the statistical significance, allowing us to conclude the statistically significant advantage of the use of the novel proposed approach.","doi":"10.3390/app11083325","issn":"2076-3417","reference":"Pereira, I., Madureira, A., Silva, ECE., Abraham, A (2021). A Hybrid Metaheuristics Parameter Tuning Approach for Scheduling through Racing and Case-Based Reasoning. APPLIED SCIENCES-BASEL. ISSN 2076-3417. Doi 10.3390/app11083325. "},{"id":"P-00T-T1H","modifiedTime":1628734496,"title":"Evaluation of an Open Source Solver to Assist on the Non-urgent Patients Transport Problem","year":"2021","authors":["Lopes, E","Costa e Silva, E"],"type":"Proceedings Paper","publicationTitle":"Advances in Intelligent Systems and Computing","abstract":"The transport of non-urgent patients is part of the daily life of the Portuguese firefighters. This type of organization seeks to optimize the allocation of resources to reduce its economic expenses and maximize the availability of resources. In this work, the needs of a fire station, that intends to minimize the route taken by ambulances transporting non-urgent patients, is addressed. This problem can be seen as a Vehicle Routing Problem with Time Windows in which each vehicle leaves the fire station, travels to the residence of non-urgent patients and, after reaching its maximum capacity in terms of maximum number of passengers or maximum time, transports them to the clinic where treatments are carried out. Also, this work intents to summarized the previous work on transport of non-urgent patients in Portugal. A Vehicle Routing Problem open source tool designed for healthcare and tourism sectors is used to test real instances extract from data provided by a Portuguese fire station. The results show that the solver may be used as a tool for assisting organizations that perform non-urgent transport. However, it is necessary to add constraints concerning time windows for the patients reaching at the treatment facilities, to minimize the delays. © 2021, The Author(s), under exclusive license to Springer Nature Switzerland AG.","doi":"10.1007/978-3-030-73050-5_38","issn":"2194-5357","reference":"Lopes, E., Costa e Silva, E (2021). Evaluation of an Open Source Solver to Assist on the Non-urgent Patients Transport Problem. Advances in Intelligent Systems and Computing. ISSN 2194-5357. Doi 10.1007/978-3-030-73050-5_38. "},{"id":"P-00T-WMZ","modifiedTime":1628737718,"title":"A mixed integer nonlinear multiperiod model for supply chain management of a company in the retail sector","year":"2021","authors":["Teixeira, A","Silva, ECE","Lopes, C"],"type":"Article","publicationTitle":"RAIRO-OPERATIONS RESEARCH","abstract":"The 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.","doi":"10.1051/ro/2021048","issn":"0399-0559","reference":"Teixeira, A., Silva, ECE., Lopes, C (2021). A mixed integer nonlinear multiperiod model for supply chain management of a company in the retail sector. RAIRO-OPERATIONS RESEARCH. ISSN 0399-0559. Doi 10.1051/ro/2021048. "},{"id":"P-00T-P3V","modifiedTime":1641404316,"title":"A Human-like Upper-limb Motion Planner: Generating naturalistic movements for humanoid robots","year":"2021","authors":["Gulletta, G","Silva, ECE","Erlhagen, W","Meulenbroek, R","Costa, MFP","Bicho, E"],"type":"Article","publicationTitle":"INTERNATIONAL JOURNAL OF ADVANCED ROBOTIC SYSTEMS","abstract":"As 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.","doi":"10.1177/1729881421998585","issn":"1729-8814","reference":"Gulletta, G., Silva, ECE., Erlhagen, W., Meulenbroek, R., Costa, MFP., Bicho, E (2021). A Human-like Upper-limb Motion Planner: Generating naturalistic movements for humanoid robots. INTERNATIONAL JOURNAL OF ADVANCED ROBOTIC SYSTEMS. ISSN 1729-8814. Doi 10.1177/1729881421998585. "},{"id":"P-00V-3SD","modifiedTime":1635265576,"title":"Unveiling the Dynamics of the European Entrepreneurial Framework Conditions over the Last Two Decades: A Cluster Analysis","year":"2021","authors":["Silva, ECE","Correia, A","Borges, A"],"type":"Article","publicationTitle":"AXIOMS","abstract":"Entrepreneurship is a theme of global interest, and it is the subject of investigations conducted by many researchers and projects. In particular, the Global Entrepreneurship Monitor project is a global project that involves several countries and years of surveys on entrepreneurship indicators. This study focuses on the 12 indicators of the entrepreneurial ecosystem defined by the Entrepreneurial Framework Conditions (EFCs). The EFCs are specifically related to the quality of the entrepreneurial ecosystem. Using clustering techniques, the present study analyzes how European experts' perceptions on the EFCs of their home country have changed between 2000 and 2019. The main finding is the existence of significant differences between the clusters obtained over the years and between countries. Therefore, in theoretical terms, this dynamical behavior in relation to the entrepreneurial conditions of economies should be considered in future works, namely, those concerning the definition of the number of clusters, which, according to the internal validation measures computed in this work, should be two.","doi":"10.3390/axioms10030149","issn":"","reference":"Silva, ECE., Correia, A., Borges, A (2021). Unveiling the Dynamics of the European Entrepreneurial Framework Conditions over the Last Two Decades: A Cluster Analysis. AXIOMS. ISSN . Doi 10.3390/axioms10030149. "},{"id":"P-00V-6R7","modifiedTime":1628115702,"title":"Guidelines for Creating Video Podcasts in Mathematics Higher Education","year":"2021","authors":["Costa, SF","Silva, ECE","Correia, A"],"type":"Article","publicationTitle":"INTERNATIONAL JOURNAL FOR TECHNOLOGY IN MATHEMATICS EDUCATION","abstract":"b-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.","doi":"10.1564/tme_v28.2.03","issn":"1744-2710","reference":"Costa, SF., Silva, ECE., Correia, A (2021). Guidelines for Creating Video Podcasts in Mathematics Higher Education. INTERNATIONAL JOURNAL FOR TECHNOLOGY IN MATHEMATICS EDUCATION. ISSN 1744-2710. Doi 10.1564/tme_v28.2.03. "},{"id":"P-00T-91K","modifiedTime":1679310179,"title":"Optimization of the grapes reception process","year":"2021","authors":["Carneiro, D","Pereira, J","Silva, ECE"],"type":"Article","publicationTitle":"NEURAL COMPUTING & APPLICATIONS","abstract":"Grapes reception is a key process in wine production. The harvest days are extremely challenging days in managing the reception of the grapes, as the winery needs to deal with the non-uniform arrival of the grapes, while guaranteeing suppliers' satisfaction and wine quality. The best management of the resources of the suppliers (i.e., grapes and trucks) and winery (i.e., grain-tanks and pressing machines) must be ensured. In this paper, the underlying optimization problem for grape reception is solved by developing a genetic algorithm (GA) tailored for this specific challenge. The results of this algorithm are compared with a FIFO policy for a typical scenario that occurs on the harvest days of a real winery. Additionally, different scenarios are simulated to assess the validity and quality of the solutions found. The results show that, using modest computational resources, it is possible to achieve better solutions with the proposed GA. This allows for the algorithm to be used in real time, even whenever plant conditions change significantly (e.g., when a new truck arrives, when a machine fails). Furthermore, the trucks and grapes waiting time for the results using the developed GA are significantly smaller than the ones observed using a FIFO approach.","doi":"10.1007/s00521-020-05620-0","issn":"0941-0643","reference":"Carneiro, D., Pereira, J., Silva, ECE (2021). Optimization of the grapes reception process. NEURAL COMPUTING & APPLICATIONS. ISSN 0941-0643. Doi 10.1007/s00521-020-05620-0. "},{"id":"P-00Q-GFM","modifiedTime":1568013686,"title":"Clustering of PP Nanocomposites Flow Curves Under Different Extrusion Conditions","year":"2020","authors":["De Almeida, F","Costa e Silva, E","Correia, A"],"type":"Proceedings Paper","publicationTitle":"Advances in Intelligent Systems and Computing","abstract":"For assessing the structural features of organoclay C15A dispersions in PP/PP-g-MA melts under different processing conditions along the screws of Twin Screw Extruder, in this work four different clustering algorithms are considered. The best algorithm and number of clusters is selected using three internal validation measures: connectedness, Dunn’s index and silhouette width. The results show that hierarchical clustering is the algorithm that yield better results and two is the best number of clusters. Two clusters are well identified L/D = 9.5 and 32. © 2020, Springer Nature Switzerland AG.","doi":"10.1007/978-3-030-14347-3_53","issn":"2194-5357","reference":"De Almeida, F., Costa e Silva, E., Correia, A (2020). Clustering of PP Nanocomposites Flow Curves Under Different Extrusion Conditions. Advances in Intelligent Systems and Computing. ISSN 2194-5357. Doi 10.1007/978-3-030-14347-3_53. "},{"id":"P-00R-MXY","modifiedTime":1604434150,"title":"A multi-model methodology for forecasting sales and returns of liquefied petroleum gas cylinders","year":"2020","authors":["Correia, A","Lopes, C","Costa e Silva, ECE","Monteiro, M","Lopes, RB"],"type":"Article","publicationTitle":"NEURAL COMPUTING & APPLICATIONS","abstract":"In the liquefied petroleum gas (LPG) cylinder business, one of the most important assets is the LPG cylinder. This work addresses the asset acquisition planning for the LPG cylinder business of a company from the energy sector which has recently started this activity. In order to make the acquisition plan, it was necessary to forecast the sales and the LPG cylinder return rate. For that purpose, an ensemble method using time series techniques, multiple linear regression models and artificial neural networks was employed. Sales forecast was obtained using time series techniques, in particular, moving averages and exponential smoothing. Then, forecast of bottled propane gas sales and return rate was also addressed through multiple linear regression and artificial neural networks. A probability density function was defined for each of the different approaches. Afterward, using Monte Carlo simulation, the forecast values are obtained by a linear combination of the probability density functions, thus producing the final forecast. Results show that the company's expectation of growth is larger than that predicted by the proposed methodology, which means the company should reflect on its current asset acquisition strategy. By combining different approaches, the proposed multi-model methodology allowed to obtain an accurate forecasting, without requiring a lot of historical data.","doi":"10.1007/s00521-020-04713-0","issn":"0941-0643","reference":"Correia, A., Lopes, C., Costa e Silva, ECE., Monteiro, M., Lopes, RB (2020). A multi-model methodology for forecasting sales and returns of liquefied petroleum gas cylinders. NEURAL COMPUTING & APPLICATIONS. ISSN 0941-0643. Doi 10.1007/s00521-020-04713-0. "},{"id":"P-00R-Z44","modifiedTime":1587812173,"title":"Inventory models with reverse logistics for assets acquisition in a liquefied petroleum gas company","year":"2020","authors":["Lopes, C","Correia, A","Silva, ECE","Monteiro, M","Lopes, RB"],"type":"Article","publicationTitle":"JOURNAL OF MATHEMATICS IN INDUSTRY","abstract":"This 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 returned cylinders cover for the demand. A third model is also proposed considering that both the demand and the returns are stochastic in nature and the replenishment from the supplier is discrete. The three models address different scenarios that the company is either currently facing or is expecting to occur in the near future.","doi":"10.1186/s13362-020-00078-0","issn":"2190-5983","reference":"Lopes, C., Correia, A., Silva, ECE., Monteiro, M., Lopes, RB (2020). Inventory models with reverse logistics for assets acquisition in a liquefied petroleum gas company. JOURNAL OF MATHEMATICS IN INDUSTRY. ISSN 2190-5983. Doi 10.1186/s13362-020-00078-0. "},{"id":"P-00S-0VN","modifiedTime":1604493903,"title":"A logistic regression model for consumer default risk","year":"2020","authors":["Costa e Silva, ECE","Lopes, IC","Correia, A","Faria, S"],"type":"Article","publicationTitle":"JOURNAL OF APPLIED STATISTICS","abstract":"In this study, a logistic regression model is applied to credit scoring data from a given Portuguese financial institution to evaluate the default risk of consumer loans. It was found that the risk of default increases with the loan spread, loan term and age of the customer, but decreases if the customer owns more credit cards. Clients receiving the salary in the same banking institution of the loan have less chances of default than clients receiving their salary in another institution. We also found that clients in the lowest income tax echelon have more propensity to default. The model predicted default correctly in 89.79% of the cases.","doi":"10.1080/02664763.2020.1759030","issn":"0266-4763","reference":"Costa e Silva, ECE., Lopes, IC., Correia, A., Faria, S (2020). A logistic regression model for consumer default risk. JOURNAL OF APPLIED STATISTICS. ISSN 0266-4763. Doi 10.1080/02664763.2020.1759030. "},{"id":"P-00R-8K5","modifiedTime":1651698753,"title":"When hotels go abroad: the internationalisation of the Portuguese hospitality","year":"2020","authors":["Braga, V","Oliveira, A","Silva, E"],"type":"Article","publicationTitle":"European J. of International Management","abstract":"","doi":"10.1504/ejim.2020.10022184","issn":"1751-6757","reference":"Braga, V., Oliveira, A., Silva, E (2020). When hotels go abroad: the internationalisation of the Portuguese hospitality. European J. of International Management. ISSN 1751-6757. Doi 10.1504/ejim.2020.10022184. "},{"id":"P-00Q-7E5","modifiedTime":1571311552,"title":"Supply Chain Purchasing Domain Optimization in a Portuguese Retail Company","year":"2019","authors":["Teixeira, A","Costa e Silva, E","Lopes, C","Santos, JF"],"type":"Proceedings Paper","publicationTitle":"Springer Proceedings in Mathematics and Statistics","abstract":"In this paper we address a case study of the purchasing management section in a Portuguese company in the Retail sector. The purchasing management costs in this company were found to depend largely on the storage mode of the products. Therefore we developed a mathematical model for optimizing the purchasing management costs. In the model we address how to order the products and which storage mode to choose, in order to minimize costs and fulfil the demand. Real instances regarding the monthly demand for one year are tested and the results show that the model can reduce the ratio between operational costs and merchandise costs in almost every instance. © 2019, Springer Nature Switzerland AG.","doi":"10.1007/978-3-030-10731-4_14","issn":"2194-1009","reference":"Teixeira, A., Costa e Silva, E., Lopes, C., Santos, JF (2019). Supply Chain Purchasing Domain Optimization in a Portuguese Retail Company. Springer Proceedings in Mathematics and Statistics. ISSN 2194-1009. Doi 10.1007/978-3-030-10731-4_14. "},{"id":"P-00Q-CG1","modifiedTime":1554303829,"title":"Internationalization strategies for tourism in Portugal","year":"2019","authors":["Oliveira, A","Braga, V","Costa e Silva, E"],"type":"Proceedings Paper","publicationTitle":"Lecture Notes in Electrical Engineering","abstract":"Tourism is one of the activities of great relevance on a global scale; with an increasing and fierce competition, needing to attract national and international tourists to maintain its distinctive position. Being considered as the Portuguese economy’s booster, and as a strong strategic activity for the future development of the country it is required to verify if: the agglomeration of tourism companies, the continuous investment on the qualification of human resources and the inherited and complementary resources influence the decision of the internationalization of the Portuguese hotels. The multivariate linear regression (MLR) analysis carried out for the Portuguese context, using a database of 2015, concludes that the agglomeration is statistically significant, whereas only some endogenous and knowledge resources are statistically significant for the internationalization of the sector. © 2019, Springer International Publishing AG, part of Springer Nature.","doi":"10.1007/978-3-319-91334-6_134","issn":"1876-1100","reference":"Oliveira, A., Braga, V., Costa e Silva, E (2019). Internationalization strategies for tourism in Portugal. Lecture Notes in Electrical Engineering. ISSN 1876-1100. Doi 10.1007/978-3-319-91334-6_134. "},{"id":"P-00Q-CG2","modifiedTime":1554303828,"title":"The impact of barrel oil price variation in MIBEL prices: A longitudinal approach","year":"2019","authors":["Borges, A","Costa e Silva, E"],"type":"Proceedings Paper","publicationTitle":"Lecture Notes in Electrical Engineering","abstract":"This paper seeks to analyse the impact of barrel oil price variation on the electricity prices. In particular, we analyse the impact of daily variation of barrel oil price on the short-term evolution of the Iberian Electricity Market (MIBEL) hourly prices, for biding optimization purpose, and also for scenario analysis in terms of pricing and strategy. The pursuit for accurate models to predict price movements can help to develop profit-maximizing trading strategies and optimal bidding techniques. In fact, important activities such as bidding strategies rely, nowadays, on price forecast information to improve decision making. For this purpose we make use of a mixed-effects longitudinal model to describe the variability of hourly prices from January 2015 to June 2016, in a total of 13 032 observations. We consider the value of barrel oil price, on the same day and on the previous day, as fixed effects, hour group as random effect and an autoregressive component of order 7 describing the within hour dependence. This analysis is an extension of [1], where the need of exogenous variables incorporation arose when analysing the longitudinal variation of electricity prices, with the purpose of enhance the longitudinal model performance. This study offers evidence that barrel oil price variation must be taken into account for electricity price forecasting, since it affects its variability. © 2019, Springer International Publishing AG, part of Springer Nature.","doi":"10.1007/978-3-319-91334-6_104","issn":"1876-1100","reference":"Borges, A., Costa e Silva, E (2019). The impact of barrel oil price variation in MIBEL prices: A longitudinal approach. Lecture Notes in Electrical Engineering. ISSN 1876-1100. Doi 10.1007/978-3-319-91334-6_104. "},{"id":"P-00Q-CG3","modifiedTime":1554303829,"title":"Scheduling in an automobile repair shop","year":"2019","authors":["de Fátima Pilar, M","Costa e Silva, E","Borges, A"],"type":"Proceedings Paper","publicationTitle":"Lecture Notes in Electrical Engineering","abstract":"Scheduling has been extensively studied since its correct application and development is a decisive factor in an organization’s success. Its application can be found in several areas of industry. In this work a real case of an automobile sector firm, more specifically the repair shop, is presented. First, a brief literature review is presented in order to gain some sensitivity on the scheduling thematic. Following with a description of the firm, detailing its repair shop, and the statistical analysis of the database provided by the firm. This analysis is intended to understand the firm’s current situation, in particular, the characterization of repairs carried out during the period under analysis. This exploratory analysis serves as the basis for a mathematical model, that will be developed in a future work, in order to support the vehicles repairment scheduling decision. © 2019, Springer International Publishing AG, part of Springer Nature.","doi":"10.1007/978-3-319-91334-6_115","issn":"1876-1100","reference":"de Fátima Pilar, M., Costa e Silva, E., Borges, A (2019). Scheduling in an automobile repair shop. Lecture Notes in Electrical Engineering. ISSN 1876-1100. Doi 10.1007/978-3-319-91334-6_115. "},{"id":"P-00Q-CG4","modifiedTime":1554303829,"title":"Optimization of purchasing management of a Portuguese company in the retail sector","year":"2019","authors":["Teixeira, A","Costa e Silva, E","Santos, JF"],"type":"Proceedings Paper","publicationTitle":"Lecture Notes in Electrical Engineering","abstract":"The current competitive environment requires greater customer orientation and better business performance to match the clients’ expectations with varied products and profitable sales prices. This has led to Supply Chain Management (SCM) as a source of competitive advantage. However, given the complexity of Supply Chain (SC) planning, optimization based quantitative models emerged as a support for decision-making. This article presents an empirical study with real data of a Portuguese company of the retail sector. In order to contribute with “tailor-for” quantitative models for improving decision-making in the company’s purchasing management, in this paper the industrial challenge and the company are introduced, followed by a preliminary data analysis. This analysis has require for deciding the real instances that will be used on the validation of the quantitative model that will be developed in future. © 2019, Springer International Publishing AG, part of Springer Nature.","doi":"10.1007/978-3-319-91334-6_107","issn":"1876-1100","reference":"Teixeira, A., Costa e Silva, E., Santos, JF (2019). Optimization of purchasing management of a Portuguese company in the retail sector. Lecture Notes in Electrical Engineering. ISSN 1876-1100. Doi 10.1007/978-3-319-91334-6_107. "},{"id":"P-00P-3B5","modifiedTime":1547822909,"title":"Parallel two-phase methods for global optimization on GPU","year":"2019","authors":["Ferreiro, AM","Garcia Rodriguez, JA","Vazquez, C","Costa e Silva, ECE","Correia, A"],"type":"Article","publicationTitle":"MATHEMATICS AND COMPUTERS IN SIMULATION","abstract":"Developing general global optimization algorithms is a difficult task, specially for functions with a huge number of local minima in high dimensions. Stochastic metaheuristic algorithms can provide the only alternative for the solution of such problems since they are aimed at guaranteeing global optimality. However, the main drawback of these algorithms is that they require a large number of function evaluations in order to skip/discard local optima, thus exhibiting a low convergence order and, as a result, a high computational cost. Furthermore, the situation can become even worse with the increase of dimension. Usually the number of local minima highly increases, as well as the computational cost of the function evaluation, thus increasing the difficulty for covering the whole search space. On the other hand, deterministic local optimization methods exhibit faster convergence rates, requiring a lower number of functions evaluations and therefore involving a lower computational cost, although they can get stuck into local minima. A way to obtain faster global optimization algorithms is to mix local and global methods in order to benefit from higher convergence rates of local ones, while retaining the global approximation properties. Another way to speedup global optimization algorithms comes from the use of efficient parallel hardware architectures. Nowadays, a good alternative is to take advantage of graphics processing units (GPUs), which are massively parallel processors and have become quite accessible cheap alternative for high performance computing. In this work a parallel implementation on GPUs of some hybrid two-phase optimization methods, that combine the metaheuristic Simulated Annealing algorithm for finding a global minimum, with different local optimization methods, namely a conjugate gradient algorithm and a version of Nelder-Mead method, is presented. The performance of parallelized versions of the above hybrid methods are analyzed for a set of well known test problems. Results show that GPUs represent an efficient alternative for the parallel implementation of two-phase global optimization methods.","doi":"10.1016/j.matcom.2018.06.005","issn":"0378-4754","reference":"Ferreiro, AM., Garcia Rodriguez, JA., Vazquez, C., Costa e Silva, ECE., Correia, A (2019). Parallel two-phase methods for global optimization on GPU. MATHEMATICS AND COMPUTERS IN SIMULATION. ISSN 0378-4754. Doi 10.1016/j.matcom.2018.06.005. "},{"id":"P-00R-Q4D","modifiedTime":1588950130,"title":"Rheological behaviour of PP nanocomposites by extrusion process","year":"2019","authors":["de Almeida, F","Costa e Silva, E","Correia, A","Silva, FJG"],"type":"Proceedings Paper","publicationTitle":"Procedia Manufacturing","abstract":"The effect of organophilic clay (C15A) in PP compatibilized polymer (PP/PP-g-MA) through rheological experimental results is presented. This study focusses on the description of the rheological behaviour of the organophilic layers along the screws of a twin screw extruder by melting process, varying the screw profile as well as the processing conditions, namely screw speed, temperature and feed rate. Different levels of dispersion were found along the screws for all conditions and positions analyzed by rheology. The qualitative analysis of the images obtained by transmission electron microscopy, reinforced the results. Furthermore, the effects of the processing conditions on dispersion of C15A layers along the screw profile are analyzed using multiple linear regression techniques. The results show statistically significant differences of all rheology measures for all the processing conditions and positions along the extruder. © 2019 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/)","doi":"10.1016/j.promfg.2020.01.135","issn":"2351-9789","reference":"de Almeida, F., Costa e Silva, E., Correia, A., Silva, FJG (2019). Rheological behaviour of PP nanocomposites by extrusion process. Procedia Manufacturing. ISSN 2351-9789. Doi 10.1016/j.promfg.2020.01.135. "},{"id":"P-00R-Q4C","modifiedTime":1588950130,"title":"Scrap production of extruded aluminum alloys by direct extrusion","year":"2019","authors":["Ferrás, AF","de Almeida, F","Costa e Silva, E","Correia, A","Silva, FJG"],"type":"Proceedings Paper","publicationTitle":"Procedia Manufacturing","abstract":"The growing globalization of the different types of market requires that companies invest, in a recurrent way, to optimize and improve all the processes inherent to their activities. Aluminium extrusion is the main industrial process used to create profiles of a fixed cross-section. This process requires appropriate processing parameters to be used, in order to produce diverse profiles and high-quality products. The company's ability to adapt and improve the productive process are differentiating factors against the competition. Thus, understand the main operations and dynamics of the companies is crucial. This work presents an empirical study concerning the extrusion process of a Portuguese company in the aluminium sector. By analysing a real data base provided by the company, the main objective is to model the aluminium extrusion process. Taking into account the variables that most influence the extrusion of different profiles, the aim is to minimize the production of scrap. First, by studying the literature in the subject, the variables that most contribute to scrap production were identified. Since the database provided by the company did not present all the variables described in literature, proxy variables were considered. Next, a multivariate linear regression model for explaining the amount of scrap taking as explanatory the identified variables was estimated. With this analysis, it was possible to identify levels of significance of the variables under study, and therefore understand how each of the variables contributes to the increase or decrease of the amount of scrap on the production of aluminium profiles. The results show that variables concerning with extrusion temperature, time, speed, pressure and die geometry are crucial to improve and control the scrap production. The obtained model will be improved, in future work, by including further variables of the extrusion process. Furthermore, factor analysis and GHML methodologies will also be considered for explaining the production of scrap and therefore improve the production process. © 2019 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/)","doi":"10.1016/j.promfg.2020.01.100","issn":"2351-9789","reference":"Ferrás, AF., de Almeida, F., Costa e Silva, E., Correia, A., Silva, FJG (2019). Scrap production of extruded aluminum alloys by direct extrusion. Procedia Manufacturing. ISSN 2351-9789. Doi 10.1016/j.promfg.2020.01.100. "},{"id":"P-00R-JC5","modifiedTime":1593807629,"title":"IT'S MATHEMATICS!: A MODELLING DAY TO DEVELOP REAL-WORLD PROBLEM SOLVING","year":"2019","authors":["Costa Silva, EC","Correia, A","De Almeida, F","Monteiro, S"],"type":"Proceedings Paper","publicationTitle":"12TH INTERNATIONAL CONFERENCE OF EDUCATION, RESEARCH AND INNOVATION (ICERI2019)","abstract":"Mathematics is a basic and structural discipline of several Higher Education courses. Despite its comprehensive application to numerous real-world situations, students frequently demonstrate low levels of engagement and negative attitudes towards mathematics, which are also translated in poor achievement. In this context, teaching approaches might make the difference to engage learners' attention and to drive them into a process of active and significant learning. The challenge here is to develop learning environments that makes mathematics an enjoyable subject, providing simultaneously a meaningful learning through the stimulation on thinking skills. One of the innovative teaching approaches that emerged under the premise of develop students' problem-solving skills, today required in most professional areas, is the Problem-Based Learning (PBL). The School of Management and Technology (ESTG), from Polytechnic of Porto (P.PORTO), Portugal, has numerous courses with subjects in different areas of Mathematics. The applications of Mathematics was a common students' question present on classes. Indeed, the students related their low motivation level to the difficulty in understanding how they could use the mathematical knowledge on their professional future. The workshop \"It's Mathematics!\" consisted in a modelling day, inspired in the PBL methodology, designed to address this challenge. This event joined students from different program courses, degree levels and future professional profiles into contact with real industrial problems (or their simplifications) and also to work in groups. In small teams, and using methods, concepts and techniques from different areas of Mathematics, students worked together in order to answer these problems with the support of a teacher. This initiative was firstly motivated by the need to develop students' awareness of the application of Mathematics in solving industrial problems, as a way to increase their motivation and engagement in their study fields. At the same time, the program aimed to train and develop problem solving, teamwork, oral and written communication. These are relevant skills for professionals in the industrial and business fields that have usually deserved less attention in traditional pedagogic methods. Since the first edition, the students showed a good receptivity to this workshop, which was demonstrated by a great enthusiasm in the closing of the initiative. They considered the event very challenging and expressed the experience of public presentation at the end of the day as very positive. As negative aspects, they reported the feeling of pressure and the short time to solve the problems. The organization is currently discussing the extension of the experience over time, moving from a one-day experience to several days throughout the semester. To determine which problems are more appropriate for different students' levels, in order to be sufficiently stimulating but simultaneously not overwhelming, continues to be a challenge for the organizers. In addition, there is the need to develop adequate instruments that could help on identifying and evaluating the impact of this event in a more systematic and formal way, in order to stimulate the continuous improvement of this experience.","doi":"10.21125/iceri.2019.1500","issn":"2340-1095","volume":"","reference":"Costa Silva, EC., Correia, A., De Almeida, F., Monteiro, S (2019). IT'S MATHEMATICS!: A MODELLING DAY TO DEVELOP REAL-WORLD PROBLEM SOLVING. 12TH INTERNATIONAL CONFERENCE OF EDUCATION, RESEARCH AND INNOVATION (ICERI2019). Vol.. ISSN 2340-1095. Doi 10.21125/iceri.2019.1500. "},{"id":"P-00N-KB5","modifiedTime":1518833438,"title":"A multinomial logistics model for perceptions on entrepreneurship","year":"2018","authors":["Costa E Silva, E","Correia, A","Braga, A","Braga, V"],"type":"Article","publicationTitle":"WSEAS Transactions on Business and Economics","abstract":"In this paper we present a multinomial logistics regression to model the experts’ perceptions about the Entrepreneurship Framework Conditions, using the most recently available data from GEM, i.e., NES 2013. The expert’s type is described by a nominal variable with five categories, i.e.: “entrepreneur” “investor, financer, banker” “policy maker” “business and support services provider” and “educator, teacher, entrepreneurship researcher”. The multinomial logistic regression model presented an overall percentage correctness of 54.1%. The results show that the odds of an experts being an “entrepreneur” over being an “educator, teacher, entrepreneurship researcher” increases with the increase in the perception of “the people working for government agencies are competent and effective in supporting new and growing firms”. The same results were found for the odds of being “investor, financer, and banker” and “policy maker”. Furthermore, the odds of being a “policy maker” over being an “educator, teacher, entrepreneurship researcher” increases with the increase of the perception of “the markets for business-to-business goods and services change dramatically from year to year”. The same effect is observed for “business and support services provider”. Additionally, the odds of being a “business and support services provider” also increases with the increase of “the anti-trust legislation is effective and well enforced”.","doi":"","issn":"1109-9526","reference":"Costa E Silva, E., Correia, A., Braga, A., Braga, V (2018). A multinomial logistics model for perceptions on entrepreneurship. WSEAS Transactions on Business and Economics. ISSN 1109-9526. Doi . "},{"id":"P-00N-M4Q","modifiedTime":1519438429,"title":"A longitudinal model for MIBEL energy prices","year":"2018","authors":["Borges, A","Silva, ECE","Covas, R"],"type":"Article","publicationTitle":"WSEAS Transactions on Systems and Control","abstract":"We propose to contribute to the problematic of Electricity Price Forecasting with a longitudinal statistical approach. We focus our interest on forecasting intra-day prices using hourly data (disaggregated data) in a multivariate approach rather than in the usually used univariate approach, by adjusting a mixed-effects longitudinal model to the Iberian Electricity Market hourly prices from January 1th 2015 to June 26th 2016, in a total of 13 032 observations. Results indicate that a longitudinal approach considering a mixed-effects model, with month and weekday as fixed effects, hour group as random effect and an AutoRegressive component of order 7 describing the within hour dependence, yield a model that explains the intra-day and intra-hour dynamics for the electricity hourly prices.","doi":"","issn":"1991-8763","reference":"Borges, A., Silva, ECE., Covas, R (2018). A longitudinal model for MIBEL energy prices. WSEAS Transactions on Systems and Control. ISSN 1991-8763. Doi . "},{"id":"P-00N-GGJ","modifiedTime":1517624435,"title":"Layered clays in PP polymer dispersion: the effect of the processing conditions","year":"2018","authors":["de Almeida, MF","Correia, A","Costa e Silva, ECE"],"type":"Article","publicationTitle":"JOURNAL OF APPLIED STATISTICS","abstract":"The effect of processing conditions of material and interfacial/ interphase properties in clay/polymer nanocomposites are usually studied through experimental results of X-ray diffraction, transmission electron microscopy and rheology mechanical tests. In this paper, the interaction of the experimental parameters and properties measure results are studied by employing multivariate analysis of variance technique. This model is used to establish relations between several material and interfacial/interphase characteristics with the processing conditions. These results are then analyzed in detail, using univariate approach (analysis of variance), to point out the existing significant relations. In general, agreement with experimental observations was found, but few other nonagreeable things are found out, which must be studied in the future. The effects of all parameters are thus determined, using these new approach, to predict the relations between material and interfacial/interphase properties, without the need to duplicate experiments in laboratory.","doi":"10.1080/02664763.2017.1284185","issn":"0266-4763","reference":"de Almeida, MF., Correia, A., Costa e Silva, ECE (2018). Layered clays in PP polymer dispersion: the effect of the processing conditions. JOURNAL OF APPLIED STATISTICS. ISSN 0266-4763. Doi 10.1080/02664763.2017.1284185. "},{"id":"P-00Q-0RV","modifiedTime":1562596265,"title":"Dispersion of the Organoclay C15A Along the Screw Profile: Using TEM to Compare PP N anocomposites Thickness","year":"2018","authors":["De Almeida, F","Costa e Silva, ECE","Correia, A"],"type":"Proceedings Paper","publicationTitle":"INTERNATIONAL CONFERENCE OF COMPUTATIONAL METHODS IN SCIENCES AND ENGINEERING 2018 (ICCMSE-2018)","abstract":"Thermomechanical stress levels have a positive impact on dispersion of layered material by extrusion process. In order to contribute to the knowledge of this process, in previous work, PP nanocomposites were laboratory melted in a co-rotating twin-screw extruder by changing the processing conditions: screw profile and speed, temperature and output. Samples of PP nanocomposite material were collected on-line along the screw for subsequent study through characterization techniques. More precisely, X-ray diffraction (XRD), rheology, transmission electron microscopy (TEM) and mechanical properties were evaluated. In this work, we discuss the influence of the processing conditions on layers dispersion in PP/PP-g-MA matrix at two positions along the screw axis (at 11 and 32 L/D). TEM is a particularly useful technique since its images provide a detail view of layers dispersion of nanoclay on polymeric materials as PP/PP-g-MA, thus helping to clarify the distributive and dispersive processes. The behavior of the nanoclay thickness found by using the TEM images is studied along the screw. Parametric and non-parametric samples tests were used to infer whether the differences found at 11 and 32 LID are statistically significant. The results show a statistically significant reduction of the thickness for almost all the conditions.","doi":"10.1063/1.5079173","issn":"0094-243X","reference":"De Almeida, F., Costa e Silva, ECE., Correia, A (2018). Dispersion of the Organoclay C15A Along the Screw Profile: Using TEM to Compare PP N anocomposites Thickness. INTERNATIONAL CONFERENCE OF COMPUTATIONAL METHODS IN SCIENCES AND ENGINEERING 2018 (ICCMSE-2018). ISSN 0094-243X. Doi 10.1063/1.5079173. "},{"id":"P-00Q-0RW","modifiedTime":1562596265,"title":"How Portuguese Experts' Perceptions on the Entrepreneurial Framework Conditions have Changed over the Years: A Benchmarking Analysis","year":"2018","authors":["Costa e Silva, ECE","Correia, A","Duarte, F"],"type":"Proceedings Paper","publicationTitle":"INTERNATIONAL CONFERENCE OF COMPUTATIONAL METHODS IN SCIENCES AND ENGINEERING 2018 (ICCMSE-2018)","abstract":"This study focus on the twelve indicators of the entrepreneurial ecosystem, defined by the Global Entrepreneurship Monitor (GEM) project - the Entrepreneurial Framework Conditions (EFCs). EFCs are relate more specifically to the quality of the entrepreneurial ecosystem. The present study analyses how experts' perceptions have changed in Portugal between 2010 and 2016 by establishing a comparative analysis between the Portuguese reality and the reality in other European countries. Based on the economic performance's similarities across countries before 2010, this study is mainly concerned with the evolution of experts' perceptions on the EFCs in Portugal and how do they differ in comparison with Italy, Greece and Spain. To achieve this goal the present study uses multivariate cluster analysis to group the European economies according to the experts' perceptions on the EFCs of their home country.","doi":"10.1063/1.5079169","issn":"0094-243X","reference":"Costa e Silva, ECE., Correia, A., Duarte, F (2018). How Portuguese Experts' Perceptions on the Entrepreneurial Framework Conditions have Changed over the Years: A Benchmarking Analysis. INTERNATIONAL CONFERENCE OF COMPUTATIONAL METHODS IN SCIENCES AND ENGINEERING 2018 (ICCMSE-2018). ISSN 0094-243X. Doi 10.1063/1.5079169. "},{"id":"P-00Q-2HW","modifiedTime":1562378781,"title":"Compatibilization effect of organophilic clays in PA6/PP polymer blend","year":"2018","authors":["De Almeida, F","Correia, A","Costa e Silva, ECE","Lopes, IC","Silva, FJG"],"type":"Proceedings Paper","publicationTitle":"28TH INTERNATIONAL CONFERENCE ON FLEXIBLE AUTOMATION AND INTELLIGENT MANUFACTURING (FAIM2018): GLOBAL INTEGRATION OF INTELLIGENT MANUFACTURING AND SMART INDUSTRY FOR GOOD OF HUMANITY","abstract":"A new approach to study the compatibilization effect of organophilic clays in PA6/PP polymer blends through experimental results tests is presented. This study focuses on the description of the interphase in compatibilization by the addition of the organoclays into the polymer PA6/PP blend by melt compounding using a Twin Screw Extruder. The experimental results variations, by addition of the organoclays in uncompatibilized and compatibilized polymer blend, are studied using parametric and non-parametric analysis of variance. For all the experimental results, significant differences between polymer blends were identified. (C) 2018 The Authors. Published by Elsevier B.V.","doi":"10.1016/j.promfg.2018.10.016","issn":"2351-9789","reference":"De Almeida, F., Correia, A., Costa e Silva, ECE., Lopes, IC., Silva, FJG (2018). Compatibilization effect of organophilic clays in PA6/PP polymer blend. 28TH INTERNATIONAL CONFERENCE ON FLEXIBLE AUTOMATION AND INTELLIGENT MANUFACTURING (FAIM2018): GLOBAL INTEGRATION OF INTELLIGENT MANUFACTURING AND SMART INDUSTRY FOR GOOD OF HUMANITY. ISSN 2351-9789. Doi 10.1016/j.promfg.2018.10.016. "},{"id":"P-00M-WK0","modifiedTime":1508945591,"title":"Application of Factor Analysis to the Water Quality in Reservoirs","year":"2017","authors":["Costa e Silva, ECE","Lopes, IC","Correia, A","Manuela Goncalves, AM"],"type":"Proceedings Paper","publicationTitle":"APPLIED MATHEMATICS AND COMPUTER SCIENCE","abstract":"In this work we present a Factor Analysis of chemical and environmental variables of the water column and hydro-morphological features of several Portuguese reservoirs. The objective is to reduce the initial number of variables, keeping their common characteristics. Using the Factor Analysis, the environmental variables measured in the epilimnion and in the hypolimnion, together with the hydromorphological characteristics of the dams were reduced from 63 variables to only 13 factors, which explained a total of 83.348% of the variance in the original data. After performing rotation using the Varimax method, the relations between the factors and the original variables got clearer and more explainable, which provided a Factor Analysis model for these environmental variables using 13 varifactors: Water quality and distance to the source, Hypolimnion chemical composition, Sulfite-reducing bacteria and nutrients, Coliforms and faecal streptococci, Reservoir depth, Temperature, Location, among other factors.","doi":"10.1063/1.4982014","issn":"0094-243X","reference":"Costa e Silva, ECE., Lopes, IC., Correia, A., Manuela Goncalves, AM (2017). Application of Factor Analysis to the Water Quality in Reservoirs. APPLIED MATHEMATICS AND COMPUTER SCIENCE. ISSN 0094-243X. Doi 10.1063/1.4982014. "},{"id":"P-00M-WK1","modifiedTime":1508945591,"title":"Hierarchical Clusters of Phytoplankton Variables in Dammed Water Bodies","year":"2017","authors":["Costa e Silva, ECE","Lopes, IC","Correia, A","Manuela Goncalves, AM"],"type":"Proceedings Paper","publicationTitle":"APPLIED MATHEMATICS AND COMPUTER SCIENCE","abstract":"In this paper a dataset containing biological variables of the water column of several Portuguese reservoirs is analyzed. Hierarchical cluster analysis is used to obtain clusters of phytoplankton variables of the phylum Cyanophyta, with the objective of validating the classification of Portuguese reservoirs previewly presented in [1] which were divided into three clusters: (1) Interior Tagus and Aguieira; (2) Douro; and (3) Other rivers. Now three new clusters of Cyanophyta variables were found. Kruskal-Wallis and Mann-Whitney tests are used to compare the now obtained Cyanophyta clusters and the previous Reservoirs clusters, in order to validate the classification of the water quality of reservoirs. The amount of Cyanophyta algae present in the reservoirs from the three clusters is significantly different, which validates the previous classification.","doi":"10.1063/1.4981978","issn":"0094-243X","reference":"Costa e Silva, ECE., Lopes, IC., Correia, A., Manuela Goncalves, AM (2017). Hierarchical Clusters of Phytoplankton Variables in Dammed Water Bodies. APPLIED MATHEMATICS AND COMPUTER SCIENCE. ISSN 0094-243X. Doi 10.1063/1.4981978. "},{"id":"P-00M-WK2","modifiedTime":1508945594,"title":"Tourism Demand in the Algarve Region: Evolution and Forecast using SVARMA models","year":"2017","authors":["Lopes, IC","Soares, F","Costa e Silva, ECE"],"type":"Proceedings Paper","publicationTitle":"APPLIED MATHEMATICS AND COMPUTER SCIENCE","abstract":"Tourism is one of the Portuguese economy's key sectors, and its relative weight has grown over recent years. The Algarve region is particularly focused on attracting foreign tourists and has built over the years a large offer of diversified hotel units. In this paper we present multivariate time series approach to forecast the number of overnight stays in hotel units (hotels, guesthouses or hostels, and tourist apartments) in Algarve. We adjust a seasonal vector autoregressive and moving averages model (SVARMA) to monthly data between 2006 and 2016. The forecast values were compared with the actual values of the overnight stays in Algarve in 2016 and led to a MAPE of 15.1% and RMSE=53847.28. The MAPE for the Hotel series was merely 4.56%. These forecast values can be used by a hotel manager to predict their occupancy and to determine the best pricing policy.","doi":"10.1063/1.4982015","issn":"0094-243X","reference":"Lopes, IC., Soares, F., Costa e Silva, ECE (2017). Tourism Demand in the Algarve Region: Evolution and Forecast using SVARMA models. APPLIED MATHEMATICS AND COMPUTER SCIENCE. ISSN 0094-243X. Doi 10.1063/1.4982015. "},{"id":"P-00N-42Y","modifiedTime":1516992068,"title":"Air Quality Assessment in Portugal and the Special Case of the Tamega e Sousa Region","year":"2017","authors":["de Almeida, F","Correia, A","Costa e Silva, ECE"],"type":"Proceedings Paper","publicationTitle":"APPLIED MATHEMATICS AND COMPUTER SCIENCE","abstract":"Air pollution is a major environmental problem which can present a significant risk for human health. This paper, presents the evaluation of the air quality in several region of Portugal. Special focus is given to the region of Tamega e Sousa where ESTG/P. Porto is located. ANOVA and MANOVA techniques are applied to study the differences between air quality in the period between 2009 and 2012 in several regions of Portugal. The data includes altitude, area, expenditure of environmental measures on protection of air quality and climate, expenditure on protection of biodiversity and landscape, burned area, number of forest fires, extractive and manufacturing industries, per municipality and per year. Using information gathered by the project QualAr about concentrations of the pollutants: CO, NO2, O-3, PM10 and SO2, an air quality indicator with five levels is consider. The results point to significant differences in the air quality for the regions and the years considered. Additionally, for identifying the factors that influence the air quality in 2012 a multivariate regression model was used. The results show statistical evidence that air quality in 2011, number of forest fires in 2012 and 2010, number of manufacturing industries per km(2) in 2012 and number of forest fires in 2010 are the variables that present a larger contribution to the quality of the air in 2012.","doi":"10.1063/1.4981982","issn":"0094-243X","reference":"de Almeida, F., Correia, A., Costa e Silva, ECE (2017). Air Quality Assessment in Portugal and the Special Case of the Tamega e Sousa Region. APPLIED MATHEMATICS AND COMPUTER SCIENCE. ISSN 0094-243X. Doi 10.1063/1.4981982. "},{"id":"P-00N-BRH","modifiedTime":1518228820,"title":"Mechanical Properties of PA6/PP Compatibilized Nanocomposites Using a Twin Screw Extruder","year":"2017","authors":["De Almeida, MF","Correia, A","Costa e Silva, ECE","Cristina Lopes, IC"],"type":"Proceedings Paper","publicationTitle":"PROCEEDINGS OF THE INTERNATIONAL CONFERENCE OF COMPUTATIONAL METHODS IN SCIENCES AND ENGINEERING 2017 (ICCMSE-2017)","abstract":"In this article, a new approach to study the compatibilization effect of organophilic clays in PA6/PP polymer blends through experimental results of mechanical tests is presented. This study focus on the description of the interphase in compatibilization by addition of the organoclays C15A and C30B into the polymer PA6/PP blend by melt compounding using a Twin Screw Extruder. The experimental results variations are studied, by addition of the organoclays in uncompatibilized polymer blend, using non-parametric analysis of variance (Kruskal-Wallis Test). For all the experimental results, significant differences are identified between the types of polymer blends. It was observed the compatibilization effect of both organophilic clays, being the differences most evident in the presence of PP modified.","doi":"10.1063/1.5012387","issn":"0094-243X","reference":"De Almeida, MF., Correia, A., Costa e Silva, ECE., Cristina Lopes, IC (2017). Mechanical Properties of PA6/PP Compatibilized Nanocomposites Using a Twin Screw Extruder. PROCEEDINGS OF THE INTERNATIONAL CONFERENCE OF COMPUTATIONAL METHODS IN SCIENCES AND ENGINEERING 2017 (ICCMSE-2017). ISSN 0094-243X. Doi 10.1063/1.5012387. "},{"id":"P-00N-TW5","modifiedTime":1544192690,"title":"Scheduling the Repairment of Aircrafts' Engines","year":"2017","authors":["Cerdeira, JO","Lopes, IC","Costa e Silva, ECE"],"type":"Proceedings Paper","publicationTitle":"2017 INTERNATIONAL CONFERENCE ON CONTROL, ARTIFICIAL INTELLIGENCE, ROBOTICS & OPTIMIZATION (ICCAIRO)","abstract":"In this paper a real world scheduling problem concerning the repair process of aircrafts' engines by TAP - Maintenance & Engineering (TAP-ME), is addressed. TAP-ME is the maintenance, repair and overhaul organization of TAP Portugal, Portugal's leading airline. A mixed integer linear programming formulation based on the flexible job shop scheduling, allowing operations to be executed on the same workstation by any processor of a given set, with the objective of minimizing the total weighted tardiness, is presented. Computational experiments on a real instance provided by TAP-ME from a regular working week were successful in finding an optimal solution. Additionally the model was tested using benchmarking instances available in literature.","doi":"10.1109/iccairo.2017.56","issn":"","reference":"Cerdeira, JO., Lopes, IC., Costa e Silva, ECE (2017). Scheduling the Repairment of Aircrafts' Engines. 2017 INTERNATIONAL CONFERENCE ON CONTROL, ARTIFICIAL INTELLIGENCE, ROBOTICS & OPTIMIZATION (ICCAIRO). ISSN . Doi 10.1109/iccairo.2017.56. "},{"id":"P-00N-4A3","modifiedTime":1508945723,"title":"Assessment of air quality in the Portuguese Tâmega e Sousa region","year":"2017","authors":["de Almeida, F","Correia, A","e Silva, EC"],"type":"Article","publicationTitle":"WSEAS Transactions on Environment and Development","abstract":"This paper, presents the evaluation of the air quality in several regions of Portugal, with special focus on the region of Tâmega e Sousa where ESTG/P.Porto is located. The ANOVA and MANOVA techniques are applied to study the differences between air quality from 2009 to 2012 in Portugal. The data used in this analysis includes altitude, area, expenditure of environmental measures on protection of air quality and climate, expenditure on protection of biodiversity and landscape, burned area, number of forest fires, extractive and manufacturing industries, per municipality and per year. A air quality indicator with five levels is proposed based on information gathered by the project QualAr about concentrations of the pollutants: CO, NO2, O3, PM10 and SO2. The results point to significant differences in the air quality both for the different regions and the years considered. Furthermore, for identifying the factors that influence the air quality in 2012 a multivariate regression model was used. The results show statistical evidences that air quality in 2011, number of forest fires in 2012 and 2010, number of manufacturing industries per km2 in 2012 and number of forest fires in 2010 are the variables that present a larger contribution to the quality of the air in 2012.","doi":"","issn":"1790-5079","reference":"de Almeida, F., Correia, A., e Silva, EC (2017). Assessment of air quality in the Portuguese Tâmega e Sousa region. WSEAS Transactions on Environment and Development. ISSN 1790-5079. Doi . "},{"id":"P-00M-H23","modifiedTime":1554756787,"title":"Time Series Data Mining for Energy Prices Forecasting: An Application to Real Data","year":"2017","authors":["Costa E Silva, ECE","Borges, A","Filomena Teodoro, MF","Andrade, MAP","Covas, R"],"type":"Proceedings Paper","publicationTitle":"INTELLIGENT SYSTEMS DESIGN AND APPLICATIONS (ISDA 2016)","abstract":"Recently, at the 119th European Study Group with Industry, the Energy Solutions Operator EDP proposed a challenge concerning electricity prices simulation, not only for risk measures purposes but also for scenario analysis in terms of pricing and strategy. The main purpose was short-term Electricity Price Forecasting (EPF). This analysis is contextualized in the study of time series behavior, in particular multi-variate time series, which is considered one of the current challenges in data mining. In this work a short-term EPF analysis making use of vector autoregressive models (VAR) with exogenous variables is proposed. The results show that the multivariate approach using VAR, with the season of the year and the type of day as exogenous variables, yield a model that explains the intra-day and intra-hour dynamics of the hourly prices.","doi":"10.1007/978-3-319-53480-0_64","issn":"2194-5357","reference":"Costa E Silva, ECE., Borges, A., Filomena Teodoro, MF., Andrade, MAP., Covas, R (2017). Time Series Data Mining for Energy Prices Forecasting: An Application to Real Data. INTELLIGENT SYSTEMS DESIGN AND APPLICATIONS (ISDA 2016). ISSN 2194-5357. Doi 10.1007/978-3-319-53480-0_64. "},{"id":"P-00N-BRR","modifiedTime":1518228821,"title":"Experts' Perceptions on the Entrepreneurial Framework Conditions","year":"2017","authors":["Correia, A","Costa e Silva, ECE","Cristina Lopes, IC","Braga, A","Braga, V"],"type":"Proceedings Paper","publicationTitle":"PROCEEDINGS OF THE INTERNATIONAL CONFERENCE OF COMPUTATIONAL METHODS IN SCIENCES AND ENGINEERING 2017 (ICCMSE-2017)","abstract":"The Global Entrepreneurship Monitor is a large scale database for internationally comparative entrepreneurship. This database includes information of more than 100 countries concerning several aspects of entrepreneurship activities, perceptions, conditions, national and regional policy, among others, in two main sources of primary data: the Adult Population Survey and the National Expert Survey. In the present work the National Expert Survey datasets for 2011, 2012 and 2013 are analyzed with the purpose of studying the effects of different type of entrepreneurship expert specialization on the perceptions about the Entrepreneurial Framework Conditions (EFCs). The results of the multivariate analysis of variance for the 2013 data show significant differences of the entrepreneurship experts when compared the 2011 and 2012 surveys. For the 2013 data entrepreneur experts are less favorable then most of the other experts to the EFCs.","doi":"10.1063/1.5012386","issn":"0094-243X","reference":"Correia, A., Costa e Silva, ECE., Cristina Lopes, IC., Braga, A., Braga, V (2017). Experts' Perceptions on the Entrepreneurial Framework Conditions. PROCEEDINGS OF THE INTERNATIONAL CONFERENCE OF COMPUTATIONAL METHODS IN SCIENCES AND ENGINEERING 2017 (ICCMSE-2017). ISSN 0094-243X. Doi 10.1063/1.5012386. "},{"id":"P-00M-3PA","modifiedTime":1516215677,"title":"Optimization in Generalized Linear Models: a Case Study","year":"2016","authors":["Costa e Silva, ECE","Correia, A","Lopes, IC"],"type":"Proceedings Paper","publicationTitle":"PROCEEDINGS OF THE INTERNATIONAL CONFERENCE ON NUMERICAL ANALYSIS AND APPLIED MATHEMATICS 2015 (ICNAAM-2015)","abstract":"The maximum likelihood method is usually chosen to estimate the regression parameters of Generalized Linear Models (GLM) and also for hypothesis testing and goodness of fit tests. The classical method for estimating GLM parameters is the Fisher scores. In this work we propose to compute the estimates of the parameters with two alternative methods: a derivative-based optimization method, namely the BFGS method which is one of the most popular of the quasi-Newton algorithms, and the PSwarm derivative-free optimization method that combines features of a pattern search optimization method with a global Particle Swarm scheme. As a case study we use a dataset of biological parameters (phytoplankton) and chemical and environmental parameters of the water column of a Portuguese reservoir. The results show that, for this dataset, BFGS and PSwarm methods provided a better fit, than Fisher scores method, and can be good alternatives for finding the estimates for the parameters of a GLM.","doi":"10.1063/1.4952094","issn":"0094-243X","reference":"Costa e Silva, ECE., Correia, A., Lopes, IC (2016). Optimization in Generalized Linear Models: a Case Study. PROCEEDINGS OF THE INTERNATIONAL CONFERENCE ON NUMERICAL ANALYSIS AND APPLIED MATHEMATICS 2015 (ICNAAM-2015). ISSN 0094-243X. Doi 10.1063/1.4952094. "},{"id":"P-00M-9WZ","modifiedTime":1499876152,"title":"MANOVA for Distinguishing Experts' Perceptions about Entrepreneurship using NES Data from GEM","year":"2016","authors":["Correia, A","Costa e Silva, ECE","Lopes, IC","Braga, A"],"type":"Proceedings Paper","publicationTitle":"Proceedings of the International Conference of Computational Methods in Sciences and Engineering 2016 (ICCMSE-2016)","abstract":"Global Entrepreneurship Monitor is a large scale database for internationally comparative entrepreneurship that includes information about many aspects of entrepreneurship activities, perceptions, conditions, national and regional policy, among others, of a large number of countries. This project has two main sources of primary data: the Adult Population Survey and the National Expert Survey. In this work the 2011 and 2012 National Expert Survey datasets are studied. Our goal is to analyze the effects of the different type of entrepreneurship expert specialization on the perceptions about the Entrepreneurial Framework Conditions. For this purpose the multivariate analysis of variance is used. Some similarities between the results obtained for the 2011 and 2012 datasets were found, however the differences between experts still exist.","doi":"10.1063/1.4968731","issn":"0094-243X","reference":"Correia, A., Costa e Silva, ECE., Lopes, IC., Braga, A (2016). MANOVA for Distinguishing Experts' Perceptions about Entrepreneurship using NES Data from GEM. Proceedings of the International Conference of Computational Methods in Sciences and Engineering 2016 (ICCMSE-2016). ISSN 0094-243X. Doi 10.1063/1.4968731. "},{"id":"P-00M-9X0","modifiedTime":1499876153,"title":"Consumer Default Risk Assessment in a Banking Institution","year":"2016","authors":["Costa e Silva, ECE","Lopes, IC","Correia, A","Faria, S"],"type":"Proceedings Paper","publicationTitle":"Proceedings of the International Conference of Computational Methods in Sciences and Engineering 2016 (ICCMSE-2016)","abstract":"Credit scoring is an application of financial risk forecasting to consumer lending. In this study, statistical analysis is applied to credit scoring data from a financial institution to evaluate the default risk of consumer loans. The default risk was found to be influenced by the spread, the age of the consumer, the number of credit cards owned by the consumer. A lower spread, a higher number of credit cards and a younger age of the borrower are factors that decrease the risk of default. Clients receiving the salary in the same banking institution of the loan have less chances of default than clients receiving their salary in another institution. We also found that clients in the lowest income tax echelon have more propensity to default.","doi":"10.1063/1.4968736","issn":"0094-243X","reference":"Costa e Silva, ECE., Lopes, IC., Correia, A., Faria, S (2016). Consumer Default Risk Assessment in a Banking Institution. Proceedings of the International Conference of Computational Methods in Sciences and Engineering 2016 (ICCMSE-2016). ISSN 0094-243X. Doi 10.1063/1.4968736. "},{"id":"P-00N-EWQ","modifiedTime":1516279410,"title":"A Mathematical Model for Supermarket Order Picking","year":"2016","authors":["Costa e Silva, E","Cruz, M","Lopes, IC","Moura, A"],"type":"Book Chapter","publicationTitle":"Mathematics in Industry - Progress in Industrial Mathematics at ECMI 2014","abstract":"","doi":"10.1007/978-3-319-23413-7_25","issn":"1612-3956","volume":"","reference":"Costa e Silva, E., Cruz, M., Lopes, IC., Moura, A (2016). A Mathematical Model for Supermarket Order Picking. Mathematics in Industry - Progress in Industrial Mathematics at ECMI 2014. Vol.. ISSN 1612-3956. Doi 10.1007/978-3-319-23413-7_25. "},{"id":"P-00M-3PB","modifiedTime":1554303829,"title":"Superquadrics Objects Representation for Robot Manipulation","year":"2016","authors":["Costa e Silva, ECE","Fernanda Costa, MF","Erlhagen, W","Bicho, E"],"type":"Proceedings Paper","publicationTitle":"PROCEEDINGS OF THE INTERNATIONAL CONFERENCE ON NUMERICAL ANALYSIS AND APPLIED MATHEMATICS 2015 (ICNAAM-2015)","abstract":"Superquadric are mathematically quite simple and have the ability to obtain a variety of shapes using low order parameterization. Furthermore they present closed-form equations and therefore can be used in the formulation of robotic movement planning problems, in particular in obstacle-avoidance and grasping constraints. In this paper we explore the modeling of objects using superquadrics. The classical nonlinear optimization problem for fitting shapes is extended by adding nonlinear constraints. The numerical results obtained by two different optimization methods are presented and a comparison of the volume of the superquadrics to the volume of simple ellipsoids is made.","doi":"10.1063/1.4952096","issn":"0094-243X","reference":"Costa e Silva, ECE., Fernanda Costa, MF., Erlhagen, W., Bicho, E (2016). Superquadrics Objects Representation for Robot Manipulation. PROCEEDINGS OF THE INTERNATIONAL CONFERENCE ON NUMERICAL ANALYSIS AND APPLIED MATHEMATICS 2015 (ICNAAM-2015). ISSN 0094-243X. Doi 10.1063/1.4952096. "},{"id":"P-00G-BBZ","modifiedTime":1516213845,"title":"Phytoplankton Analysis of Portuguese Reservoirs: A Cluster Analysis with R","year":"2015","authors":["Correia, A","Lopes, IC","Costa e Silva, ECE","Cabecinha, E"],"type":"Proceedings Paper","publicationTitle":"PROCEEDINGS OF THE INTERNATIONAL CONFERENCE OF NUMERICAL ANALYSIS AND APPLIED MATHEMATICS 2014 (ICNAAM-2014)","abstract":"In this work, cluster analysis is applied to a real dataset of biological features of several Portuguese reservoirs. All the statistical analysis is done using R statistical software. Several metrics and methods were explored, as well as the combination of Euclidean metric and the hierarchicalWard method. Although it did not present the best combination in terms of internal and stability validation, it was still a good solution and presented good results in terms of interpretation of the problem at hand.","doi":"10.1063/1.4913053","issn":"0094-243X","reference":"Correia, A., Lopes, IC., Costa e Silva, ECE., Cabecinha, E (2015). Phytoplankton Analysis of Portuguese Reservoirs: A Cluster Analysis with R. PROCEEDINGS OF THE INTERNATIONAL CONFERENCE OF NUMERICAL ANALYSIS AND APPLIED MATHEMATICS 2014 (ICNAAM-2014). ISSN 0094-243X. Doi 10.1063/1.4913053. "},{"id":"P-00G-BCK","modifiedTime":1450299477,"title":"Nonlinear Optimization for Human-like Synchronous Movements of a Dual Arm-hand Robotic System","year":"2015","authors":["Gulletta, G","Araujo, SM","Costa E Silva, ECE","Costa, MF","Erlhagen, W","Bicho, E"],"type":"Proceedings Paper","publicationTitle":"PROCEEDINGS OF THE INTERNATIONAL CONFERENCE OF NUMERICAL ANALYSIS AND APPLIED MATHEMATICS 2014 (ICNAAM-2014)","abstract":"In previous work we have presented a model capable of generating human-like movements for a dual arm-hand robot involved in human-robot cooperative tasks. However, the focus was on the generation of reach-to-grasp and reach-to-regrasp bimanual movements and no synchrony in timing was taken into account. In this paper we extend the previous model in order to accomplish bimanual manipulation tasks by synchronously moving both arms and hands of an anthropomorphic robotic system. Specifically, the new extended model has been designed for two different tasks with different degrees of difficulty. Numerical results were obtained by the implementation of the IPOPT solver embedded in our MATLAB simulator.","doi":"10.1063/1.4912427","issn":"0094-243X","reference":"Gulletta, G., Araujo, SM., Costa E Silva, ECE., Costa, MF., Erlhagen, W., Bicho, E (2015). Nonlinear Optimization for Human-like Synchronous Movements of a Dual Arm-hand Robotic System. PROCEEDINGS OF THE INTERNATIONAL CONFERENCE OF NUMERICAL ANALYSIS AND APPLIED MATHEMATICS 2014 (ICNAAM-2014). ISSN 0094-243X. Doi 10.1063/1.4912427. "},{"id":"P-00G-BD6","modifiedTime":1450245443,"title":"Global vs. Local Nonlinear Optimization Techniques for Human-Like Movement of an Anthropomorphic Robot","year":"2015","authors":["Silva, ECE","Costa, MF","Erlhagen, W","Bicho, E"],"type":"Proceedings Paper","publicationTitle":"PROCEEDINGS OF THE INTERNATIONAL CONFERENCE OF NUMERICAL ANALYSIS AND APPLIED MATHEMATICS 2014 (ICNAAM-2014)","abstract":"In this paper a comparison between using global and local optimization techniques for solving the problem of generating human-like arm and hand movements for an anthropomorphic dual arm robot is made. Although the objective function involved in each optimization problem is convex, there is no evidence that the admissible regions of these problems are convex sets. For the sequence of movements for which the numerical tests were done there were no significant differences between the optimal solutions obtained using the global and the local techniques. This suggests that the optimal solution obtained using the local solver is indeed a global solution.","doi":"10.1063/1.4912424","issn":"0094-243X","reference":"Silva, ECE., Costa, MF., Erlhagen, W., Bicho, E (2015). Global vs. Local Nonlinear Optimization Techniques for Human-Like Movement of an Anthropomorphic Robot. PROCEEDINGS OF THE INTERNATIONAL CONFERENCE OF NUMERICAL ANALYSIS AND APPLIED MATHEMATICS 2014 (ICNAAM-2014). ISSN 0094-243X. Doi 10.1063/1.4912424. "},{"id":"P-00G-BH6","modifiedTime":1435370912,"title":"Towards human-like bimanual movements in anthropomorphic robots: A nonlinear optimization approach","year":"2015","authors":["e Silva, EC","Costa, MFP","Araujo, JP","Machado, D","Louro, L","Erlhagen, W","Bicho, E"],"type":"Article","publicationTitle":"Applied Mathematics and Information Sciences","abstract":"Previously we have presented a model for generating human-like arm and hand movements on an unimanual anthropomorphic robot involved in human-robot collaboration tasks. The present paper aims to extend our model in order to address the generation of human-like bimanual movement sequences which are challenged by scenarios cluttered with obstacles. Movement planning involves large scale nonlinear constrained optimization problems which are solved using the IPOPT solver. Simulation studies show that the model generates feasible and realistic hand trajectories for action sequences involving the two hands. The computational costs involved in the planning allow for real-time human robot-interaction. A qualitative analysis reveals that the movements of the robot exhibit basic characteristics of human movements. © 2015 NSP.","doi":"10.12785/amis/090210","issn":"1935-0090","reference":"e Silva, EC., Costa, MFP., Araujo, JP., Machado, D., Louro, L., Erlhagen, W., Bicho, E (2015). Towards human-like bimanual movements in anthropomorphic robots: A nonlinear optimization approach. Applied Mathematics and Information Sciences. ISSN 1935-0090. Doi 10.12785/amis/090210. "},{"id":"P-008-GQH","modifiedTime":1450245360,"title":"Generating Human-like Movements on an Anthropomorphic Robot using an Interior Point Method","year":"2013","authors":["Costa e Silva, ECE","Araujo, JP","Machado, D","Costa, MF","Erlhagen, W","Bicho, E"],"type":"Proceedings Paper","publicationTitle":"11TH INTERNATIONAL CONFERENCE OF NUMERICAL ANALYSIS AND APPLIED MATHEMATICS 2013, PTS 1 AND 2 (ICNAAM 2013)","abstract":"In previous work we have presented a model for generating human-like arm and hand movements on an anthropomorphic robot involved in human-robot collaboration tasks. This model was inspired by the Posture-Based Motion-Planning Model of human movements. Numerical results and simulations for reach-to-grasp movements with two different grip types have been presented previously. In this paper we extend our model in order to address the generation of more complex movement sequences which are challenged by scenarios cluttered with obstacles. The numerical results were obtained using the IPOPT solver, which was integrated in our MATLAB simulator of an anthropomorphic robot.","doi":"10.1063/1.4825563","issn":"0094-243X","reference":"Costa e Silva, ECE., Araujo, JP., Machado, D., Costa, MF., Erlhagen, W., Bicho, E (2013). Generating Human-like Movements on an Anthropomorphic Robot using an Interior Point Method. 11TH INTERNATIONAL CONFERENCE OF NUMERICAL ANALYSIS AND APPLIED MATHEMATICS 2013, PTS 1 AND 2 (ICNAAM 2013). ISSN 0094-243X. Doi 10.1063/1.4825563. "},{"id":"P-005-436","modifiedTime":1550140924,"title":"The Power of Prediction: Robots that Read Intentions","year":"2012","authors":["Bicho, E","Erlhagen, W","Sousa, E","Louro, L","Hipolito, N","Silva, EC","Silva, R","Ferreira, F","Machado, T","Hulstijn, M","Maas, Y","de Bruijn, E","Cuijpers, RH","Newman Norlund, R","van Schie, H","Meulenbroek, RGJ","Bekkering, H"],"type":"Proceedings Paper","publicationTitle":"2012 IEEE/RSJ INTERNATIONAL CONFERENCE ON INTELLIGENT ROBOTS AND SYSTEMS (IROS)","abstract":"Humans are experts in cooperating in a smooth and proactive manner. Action and intention understanding are critical components of efficient joint action. In the context of the EU Integrated Project JAST [16] we have developed an anthropomorphic robot endowed with these cognitive capacities. This project and respective robot (ARoS) is the focus of the video. More specifically, the results illustrate crucial cognitive capacities for efficient and successful human-robot collaboration such as goal inference, error detection and anticipatory action selection. Results were considered one of the ICT \"success stories\" [22].","doi":"10.1109/iros.2012.6386297","issn":"2153-0858","volume":"","reference":"Bicho, E., Erlhagen, W., Sousa, E., Louro, L., Hipolito, N., Silva, EC., Silva, R., Ferreira, F., Machado, T., Hulstijn, M., Maas, Y., de Bruijn, E., Cuijpers, RH., Newman Norlund, R., van Schie, H., Meulenbroek, RGJ., Bekkering, H (2012). The Power of Prediction: Robots that Read Intentions. 2012 IEEE/RSJ INTERNATIONAL CONFERENCE ON INTELLIGENT ROBOTS AND SYSTEMS (IROS). Vol.. ISSN 2153-0858. Doi 10.1109/iros.2012.6386297. "},{"id":"P-002-W8C","modifiedTime":1450201576,"title":"Nonlinear Optimization for Human-Like Movements of a High Degree of Freedom Robotics Arm-Hand System","year":"2011","authors":["Costa e Silva, ECE","Costa, F","Bicho, E","Erlhagen, W"],"type":"Proceedings Paper","publicationTitle":"COMPUTATIONAL SCIENCE AND ITS APPLICATIONS - ICCSA 2011, PT III","abstract":"The design of autonomous robots, able to closely cooperate with human users in shared tasks, provides many new challenges for robotics research. Compared to industrial applications, robots working in human environments will need to have human-like abilities in their cognitive and motor behaviors. Here we present a model for generating trajectories of a high degree of freedom robotics arm-hand system that reflects optimality principles of human motor control. The process of finding a human-like trajectory among all possible solutions is formalized as a large-scale nonlinear optimization problem. We compare numerically three existing solvers, IPOPT, KNITRO and SNOPT, in terms of their real-time performance in different reach-to-grasp problems that are part of a human-robot interaction task. The results show that the SQP methods obtain better results than the IP methods. SNOPT finds optimal solutions for all tested problems in competitive computational times, thus being the one that best serves our purpose.","doi":"10.1007/978-3-642-21931-3_26","issn":"0302-9743","reference":"Costa e Silva, ECE., Costa, F., Bicho, E., Erlhagen, W (2011). Nonlinear Optimization for Human-Like Movements of a High Degree of Freedom Robotics Arm-Hand System. COMPUTATIONAL SCIENCE AND ITS APPLICATIONS - ICCSA 2011, PT III. ISSN 0302-9743. Doi 10.1007/978-3-642-21931-3_26. "},{"id":"P-002-KXM","modifiedTime":1450219834,"title":"Neuro-cognitive mechanisms of decision making in joint action: A human-robot interaction study","year":"2011","authors":["Bicho, E","Erlhagen, W","Louro, L","Costa e Silva, ECE"],"type":"Article","publicationTitle":"HUMAN MOVEMENT SCIENCE","abstract":"In this paper we present a model for action preparation and decision making in cooperative tasks that is inspired by recent experimental findings about the neuro-cognitive mechanisms supporting joint action in humans. It implements the coordination of actions and goals among the partners as a dynamic process that integrates contextual cues, shared task knowledge and predicted outcome of others' motor behavior. The control architecture is formalized by a system of coupled dynamic neural fields representing a distributed network of local but connected neural populations. Different pools of neurons encode task-relevant information about action means, task goals and context in the form of self-sustained activation patterns. These patterns are triggered by input from connected populations and evolve continuously in time under the influence of recurrent interactions. The dynamic model of joint action is evaluated in a task in which a robot and a human jointly construct a toy object. We show that the highly context sensitive mapping from action observation onto appropriate complementary actions allows coping with dynamically changing joint action situations.","doi":"10.1016/j.humov.2010.08.012","issn":"0167-9457","reference":"Bicho, E., Erlhagen, W., Louro, L., Costa e Silva, ECE (2011). Neuro-cognitive mechanisms of decision making in joint action: A human-robot interaction study. HUMAN MOVEMENT SCIENCE. ISSN 0167-9457. Doi 10.1016/j.humov.2010.08.012. "},{"id":"P-002-WMF","modifiedTime":1450245098,"title":"Human-Like Movement of an Anthropomorphic Robot: Problem Revisited","year":"2011","authors":["e Silva, EC","Costa, MF","Bicho, E","Erlhagen, W","Simos, TE","Psihoyios, G","Tsitouras, C","Anastassi, Z"],"type":"Proceedings Paper","publicationTitle":"NUMERICAL ANALYSIS AND APPLIED MATHEMATICS ICNAAM 2011: INTERNATIONAL CONFERENCE ON NUMERICAL ANALYSIS AND APPLIED MATHEMATICS, VOLS A-C","abstract":"Human-like movement is fundamental for natural human-robot interaction and collaboration. We have developed in a model for generating arm and hand movements an anthropomorphic robot. This model was inspired by the Posture-Based Motion-Planning Model of human reaching and grasping movements. In this paper we present some changes to the model we have proposed in [4] and test and compare different nonlinear constrained optimization techniques for solving the large-scale nonlinear constrained optimization problem that rises from the discretization of our time-continuous model. Furthermore, we test different time discretization steps.","doi":"10.1063/1.3636848","issn":"0094-243X","reference":"e Silva, EC., Costa, MF., Bicho, E., Erlhagen, W., Simos, TE., Psihoyios, G., Tsitouras, C., Anastassi, Z (2011). Human-Like Movement of an Anthropomorphic Robot: Problem Revisited. NUMERICAL ANALYSIS AND APPLIED MATHEMATICS ICNAAM 2011: INTERNATIONAL CONFERENCE ON NUMERICAL ANALYSIS AND APPLIED MATHEMATICS, VOLS A-C. ISSN 0094-243X. Doi 10.1063/1.3636848. "},{"id":"P-00H-MNM","modifiedTime":1450246116,"title":"A dynamic field approach to goal inference, error detection and anticipatory action selection in human-robot collaboration","year":"2011","authors":["Bicho, E","Erlhagen, W","Louro, L","Silva, ECe","Silva, R","Hipolito, N"],"type":"Book Chapter","publicationTitle":"Advances in Interaction Studies - New Frontiers in Human–Robot Interaction","abstract":"","doi":"10.1075/ais.2.10bic","issn":"1879-873X","volume":"","reference":"Bicho, E., Erlhagen, W., Louro, L., Silva, ECe., Silva, R., Hipolito, N (2011). A dynamic field approach to goal inference, error detection and anticipatory action selection in human-robot collaboration. Advances in Interaction Studies - New Frontiers in Human–Robot Interaction. Vol.. ISSN 1879-873X. Doi 10.1075/ais.2.10bic. "},{"id":"P-008-V09","modifiedTime":1499966552,"title":"Goal inferencing and error detection in joint action","year":"2010","authors":["Bicho, E","Erlhagen, W","Hulstijn, M","Maas, Y","Louro, L","Hipolito, N","E Silva, EC","De Bruijn, E","Cuijpers, R","Newman Norlund, R","Van Schie, H","Meulenbroek, R","Bekkering, H"],"type":"Proceedings Paper","publicationTitle":"4th International Conference on Cognitive Systems, CogSys 2010","abstract":"","doi":"","issn":"","volume":"","reference":"Bicho, E., Erlhagen, W., Hulstijn, M., Maas, Y., Louro, L., Hipolito, N., E Silva, EC., De Bruijn, E., Cuijpers, R., Newman Norlund, R., Van Schie, H., Meulenbroek, R., Bekkering, H (2010). Goal inferencing and error detection in joint action. 4th International Conference on Cognitive Systems, CogSys 2010. Vol.. ISSN . Doi . "},{"id":"P-007-R3C","modifiedTime":1426439375,"title":"Collision-avoidance characteristics of grasping: Early signs in hand and arm kinematics","year":"2009","authors":["Lommertzen, J","Costa E Silva, E","Cuijpers, RH","Meulenbroek, RGJ"],"type":"Proceedings Paper","publicationTitle":"Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics)","abstract":"Grasping an object successfully implies avoiding colliding into it before the hand is closed around the object. The present study focuses on prehension kinematics that typically reflect collision-avoidance characteristics of grasping movements. Twelve participants repeatedly grasped vertically-oriented cylinders of various heights, starting from two starting positions and performing the task at two different speeds. Movements of trunk, arm and hand were recorded by means of a 3D motion-tracking system. The results show that cylinder-height moderated the approach phase as expected: small cylinders induced grasps from above whereas large cylinders elicited grasps from the side. The collision-avoidance constraint proved not only to be accommodated by aperture overshoots but its effects already showed up early on as differential adaptations of the distal upper limb parameters. We discuss some implications of the present analysis of grasping movements for designing anthropomorphic robots. © 2009 Springer Berlin Heidelberg.","doi":"10.1007/978-3-642-02565-5_11","issn":"0302-9743","reference":"Lommertzen, J., Costa E Silva, E., Cuijpers, RH., Meulenbroek, RGJ (2009). Collision-avoidance characteristics of grasping: Early signs in hand and arm kinematics. Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics). ISSN 0302-9743. Doi 10.1007/978-3-642-02565-5_11. "},{"id":"P-00H-0V5","modifiedTime":1547766040,"title":"Collision-Avoidance Characteristics of Grasping","year":"2009","authors":["Lommertzen, J","Costa e Silva, E","Cuijpers, RH","Meulenbroek, RGJ"],"type":"Book Chapter","publicationTitle":"ANTICIPATORY BEHAVIOR IN ADAPTIVE LEARNING SYSTEMS: FROM PSYCHOLOGICAL THEORIES TO ARTIFICIAL COGNITIVE SYSTEMS","abstract":"","doi":"10.1007/978-3-642-02565-5_11","issn":"0302-9743","reference":"Lommertzen, J., Costa e Silva, E., Cuijpers, RH., Meulenbroek, RGJ (2009). Collision-Avoidance Characteristics of Grasping. ANTICIPATORY BEHAVIOR IN ADAPTIVE LEARNING SYSTEMS: FROM PSYCHOLOGICAL THEORIES TO ARTIFICIAL COGNITIVE SYSTEMS. ISSN 0302-9743. Doi 10.1007/978-3-642-02565-5_11. "}]