ENIDH - EMM - Engenharia de Máquinas Marítimas
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- A Multi-agent Control Architecture for Supply Chains Using a Predictive Pull-Flow PerspectivePublication . Nabais, J. Lemos; Negenborn, Rudy R.; Benítez, R. B. Carmona; Mendonça, Luís F.; Lourenço, João; Botto, M. AyalaSupply chains are large-scale distribution networks in which multiple types of commodities are present. In this paper, the operations management in supply chains is posed as a tracking control problem. All inventory levels in the network should be kept as close as possible to the desired values over time. The supply chain state is disturbed due to client demand at the end nodes. A multi-agent control architecture to restore all inventory levels over the supply chain is proposed. First the model for the supply chain is broken down into smaller subsystems using a flow decomposition. The operations management for each subsystem will be decided upon by a dedicated control agent. The control agents solve their problems using a pull-flow perspective, starting at the end nodes and then propagating upstream. Adding new components to the supply chain will have as a consequence the inclusion of more control agents. The proposed architecture is easily scalable to large supply chains due to its modular feature. The multi-agent control architecture performance is illustrated using a supply chain composed of four levels (suppliers, consolidation, distribution, end nodes) using different levels of predictions about client demands. With the increase of prediction demand accuracy the proposed control architecture is able to keep the desired inventory level at the end nodes over time, which makes it suitable for use for just in time production strategies.
- Crankshaft failure analysis of a motor vehiclePublication . Fonte, M.; Li, Bin; Reis, L.; Freitas, M.A case study of a crankshaft catastrophic failure of a motor vehicle and its failure analysis is presented. The crankshaft suffered a mechanical seizure on the crankpin no. 2 after 3 years in service. It was repaired and after 30,000 km the vehicle had a damage again, with a catastrophic failure on the same crankpin. A transversal macrograph of the crankpin revealed that the crankpin was rectified and filled with a metal alloy for the same nominal diameter. Two fatigue cracks growing to the center of the crankpin where the final fracture occurred. The symmetric semi-elliptical crack front profile confirms the effect of a pure mode I under alternating bending. The catastrophic failure was a consequence of the inadequate repairing by a non-authorized manufacturer.
- Modified binary PSO for feature selection using SVM applied to mortality prediction of septic patientsPublication . Vieira, Susana M.; Mendonça, Luís F. Mendonça; Farinha, Gonçalo J.; Sousa, João Miguel da CostaThis paper proposes a modified binary particle swarm optimization (MBPSO) method for feature election with the simultaneous optimization of SVM kernel parameter setting, applied to mortality prediction in septic patients. An enhanced version of binary particle swarm optimization, designed to cope with premature convergence of the BPSO algorithm is proposed. MBPSO control the swarm variability using the velocity and the similarity between best swarm solutions. This paper uses support vector machines in a wrapper approach, where the kernel parameters are optimized at the same time. The approach is applied to predict the outcome (survived or deceased) of patients with septic shock. Further, MBPSO is tested in several benchmark datasets and is compared with other PSO based algorithms and genetic algorithms (GA). The experimental results showed that the proposed approach can correctly select the discriminating input features and also achieve high classification accuracy, specially when compared to other PSO based algorithms. When compared to GA, MBPSO is similar in terms of accuracy, but the subset solutions have less selected features.
- The Stream‐basedService‐Centered Calculus: a Foundation for Service‐Oriented ProgrammingPublication . Cruz-Filipe, L.; Lanese, I.; Ravara, A.; Vasconcelos, V.We give a formal account of stream-based, service-centered calculus (SSCC), a calculus for modelling service-based systems, suitable to describe both service composition (orchestration) and the protocols that services follow when invoked (conversation). The calculus includes primitives for defining and invoking services, for isolating conversations (called sessions) among clients and servers, and for orchestrating services. The calculus is equipped with a reduction and a labelled transition semantics related by an equivalence result. SSCC provides a good trade-off between expressive power for modelling and simplicity for analysis. We assess the expressive power by modelling van der Aalst workflow patterns and an automotive case study from the European project Sensoria. For analysis, we present a simple type system ensuring compatibility of client and service protocols. We also study the behavioural theory of the calculus, highlighting some axioms that capture the behaviour of the different primitives. As a final application of the theory, we define and prove correct some program transformations. These allow to start modelling a system from a typical UML Sequence Diagram, and then transform the specification to match the service-oriented programming style, thus simplifying its implementation using web services technology.
- Participative Approaches to the Portuguese Maritime ClusterPublication . Simões, A.; Salvador, R; e Guedes Soares, CAs a public good, sea must be enjoyed and preserved according to the will of the majority of citizens. In order to do that, marine and maritime resources management must be accomplished through participative and democratic processes that increase the probability of correct decisions. The development of a participative sea-related process ought to facilitate the emergence of more creative and reality-adjusted solutions. The paper presents both the results of an inquiry launched to the seventy members (companies and public institutions) of the “Maritime Economy Entrepreneurship Forum” (MEEF) and the synthesis of a Delphi panel–type methodology based on fifteen maritime experts’ opinions. Based in these results, the authors propose a strategy in line with the UNESCO “Community-Based Strategy” (CBS).
- Production of extracts from preserved olives using supercritical CO2 and preliminary evaluation of its polyphenol contentPublication . Cebola, Maria João; Rijo, PatriciaThe supercritical fluid extraction (SFE) technique was used to obtain extracts from a sample simulating an olive pomace, obtained from preserved olives. The objective was to achieve the extraction of polyphenolic components from this matrix which is considered a hazardous waste from the production of olive oil. The supercritical fluid used was carbon dioxide and the SFE studies were conducted in two stages, the first at a pressure of 200 bar and 40 ºC and the second stage at 300 bar, 45 ºC and using ethanol as co-solvent. In both cases the SFE was performed for 3 hours. The first stage was carried out to obtain a cleaner matrix and the second step was aimed at the components of interest. The overall mass yield obtained was 5.5 %. Preliminary HPLC screening of the samples obtained and also of the water in which the olives were preserved showed that the polyphenol compounds were mostly in the latter.
- Multipliers, linkages and influence fields among the sectors of the Portuguese maritime clusterPublication . Simões, A.; Salvador, R.; Guedes Soares, C.The main objective of this paper is to present the multiplier effects on the Portuguese economy of the main maritime sectors and their comparison with other economic sectors, in particular the key activities of which they are suppliers or buyers. One way of evaluating economic activities, which is adopted in this paper, is through the sectorial linkage indices and their interdependence, displaying their direct, indirect and induced effects, which can be quantified with the use of the Leontief (input-output) matrix. Based on the input-output matrix, one obtains the interconnection coefficients, the multiplying factors and the influence fields. Based on the values of the interdependence coefficients, the economic activities are analyzed and classified by its importance to the national economy. The paper identifies a broadly diversified productive structure, with several key sectors, which, if stimulated, can significantly boost the growth of other sectors and the overall economy.
- Hierarchical MPC for Multi-Commodity Transportation NetworksPublication . Nabais, João Lemos; Negenborn, Rudy R.; Carmona-Benítez, Rafael Bernardo; Mendonça, Luís Filipe; Botto, Miguel AyalaTransportation networks are large scale complex systems spatially distributed whose objective is to deliver commodities at the agreed time and at the agreed location. These networks appear in different domain fields, such as communication, water distribution, traffic, logistics and transportation. A transportation network has at the macroscopic level storage capability (located in the nodes) and transport delay (along each connection) as main features. Operations management at transportation networks can be seen as a flow assignment problem. The problem dimension to solve grows exponentially with the number of existing commodities, nodes and connections. In this work we present a Hierarchical Model Predictive Control (H-MPC) architecture to determine flow assignments in transportation networks, while minimizing exogenous inputs effects. This approach has the capacity to keep track of commodity types while solving the flow assignment problem. A flow decomposition of the main system into subsystems is proposed to diminish the problem dimension to solve in each time step. Each subsystem is managed by a control agent. Control agents solve their problems in a hierarchical way, using a so-called push-pull flow perspective. Further problem dimension reduction is achieved using contracted projection sets. The framework proposed can be easily scaled to network topologies in which hundreds of commodities and connections are present.
- Influence of Milling and Abrasive Waterjet Cutting on the Fatigue Behaviour of DP600 Steel SheetPublication . Duarte, Pedro; Infante, Virgínia; Freitas, Manuel deThe observation of cracks in mechanical parts shows that cracks often initiate on cutting edges. A lot of effort has been done to developing theories to predict fatigue behaviour of welds. However for the cut-edges available data is very scarce on the fatigue behaviour. This paper presents the results obtained in fatigue tests on DP600 dual-phase steel sheet specimens, under three types of cutting edges processes: milling with two cutting parameters and abrasive waterjet cutting. The tests were carried out using smooth specimens (Kt=1)and with a fatigue constant amplitude loading with R=0.1. Surface roughness and residual stresses induced by these different cutting conditions were measured and analysed. It was found that the fatigue strength of the abrasive waterjet cutting specimens was smaller than the predicted fatigue strength of the milling specimens and these may be attributed to the surface roughness induced by the cutting process. Finally failure mechanisms were studied with the scanning electron microscope (SEM) at fracture surfaces, including the identification of the fatigue crack initiation region. It was also observed that fatigue crack initiation takes place on the cut-edges.
- Benchmark exact solutions for the static analysis of multilayered piezoelectric composite plates using PVDFPublication . Moleiro, F; Soares, C.M. Mota; Soares, C.A. Mota; Reddy, J.N.The three-dimensional (3D) exact solutions developed in the early 1970s by Pagano for simply supported multilayered orthotropic composite plates and later in the 1990s extended to piezoelectric plates by Heyliger have been extremely useful in the assessment and development of advanced laminated plate theories and related finite element models. In fact, the well-known test cases provided by Pagano and by Heyliger in those earlier works are still used today as benchmark solutions. However, the limited number of test cases whose 3D exact solutions have been published has somewhat restricted the assessment of recent advanced models to the same few test cases. This work aims to provide additional test cases to serve as benchmark exact solutions for the static analysis of multilayered piezoelectric composite plates. The method introduced by Heyliger to derive the 3D exact solutions has been successfully implemented using symbolic computing and a number of new test cases are here presented thoroughly. Specifically, two multilayered plates using PVDF piezoelectric material are selected as test cases under two different loading conditions and considering three plate aspect ratios for thick, moderately thick and thin plate, in a total of 12 distinct test cases. (C) 2013 Elsevier Ltd. All rights reserved.