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- Speed Control of an Experimental Pneumatic EnginePublication . Pardelhas, João; Silva, Miguel; Mendonça, Luis; Baptista, Luis
- Solution Verification of CFD Simulations of a Drowning Body at SeaPublication . Ribeiro e Silva, S.; Eça, L.This works aims at evaluating the ability of assessing drifting of a drowning body at sea using Computational Fluid Dynamics (CFD). This paper is focused on the evaluation of the numerical accuracy of the CFD simulations performed with the Simerics-MP flow solver, i.e., solution verification. The main goal of the paper is to illustrate the challenges found when using a commercial CFD package. The study of the drift of a drowning body at sea involves the simulation of incompressible, two-phase (air and water) flows around a bluff body and so the simplest mathematical model to tackle it is the Reynolds-averaged Navier-Stokes equations using ensemble average to define the mean flow and to average mass and momentum balances. This leads to unsteady flow problems that require integration in space and time. Therefore, numerical errors include contributions from the round-off, iterative, discretization (time and space) and statistical errors. Two simple situations to address the difficulties of estimating numerical uncertainties in the simulation of the drift of a drowning body at sea have been selected: (i) current induced drag forces, no wind and no waves; (ii) wind induced drag forces, no current and no waves. Grid/time refinement studies are performed for the two selected conditions to determine numerical uncertainties of the three selected quantities of interest: the resistance/drag force and the trim (pitch) and sinkage (heave) of the drowning body. It is clear that “default settings” cannot be used for such exercise and that there are small details that may have a significant influence on the estimated uncertainties. Nonetheless, the results show that it is not easy to obtain negligible numerical uncertainties in this type of simulations and so the planned comparison of simulations and experiments to determine the modelling error of CFD will be affected by a significant validation uncertainty.
- An optimisation-based approach to reduce fuel consumption and emissions from shipping navigationPublication . Silva, S. Ribeiro e; Moreira, M. BentoThis study presents an optimisation-based approach to reduce fuel consumption and emissions from shipping navigation. The main objective is to improve energy efficiency and simultaneously turn a case-study vessel compliant with Carbon Intensity Indicator (CII) proposed by IMO. This optimisation module has been devised as part of a new robust integrated real-time digital solution that will involve a significant number of both technical and operational measures in practice aiming to optimise operational efficiency (during navigation and port calls). Namely, the tool will be capable of situational awareness and decision support to reduce fuel consumption and Green House Gas (GHG) emissions from shipping and must be combined with intrinsic vessel systems to improve vessel hydrodynamic performance, resulting also in improved vessel safety and widening of the operational weather window
- Some topological properties of the sets of non-negative Wigner functionsPublication . Dias, N. C.The set of non-negative Wigner functions is a convex set which, in the finite dimensional case, is compact and equal to the convex hull of its extreme points. Thus, in finite dimensions, these particular (extreme) Wigner functions can be used to generate the entire set of non-negative Wigner functions. We show that the extreme Wigner functions can be identified by the properties of their null sets, and discuss the problem of constructing these states explicitly. As a by-product, we also elaborate on the properties of the interior and the boundary of the set of non-negative Wigner functions. Finally, if time permits, we will discuss the difficulties of extending some of these results to the infinite dimensional case.
- Intelligent Fault Diagnosis of Marine EquipmentsPublication . Mendonça, L. F.; Vieira, S. M.; Sousa, J. M. C.The automatic and intelligent diagnosis of faults in marine equipment is a task that is considered to be of great importance considering the numerous tasks that are associated with professionals working on ships. The possibility of including automatic and intelligent processes on a ship makes it possible to monitor equipment more effectively and make more informed decisions. This approach has received a lot of attention in the academic and industrial fields as it can offer considerable economic and safety advantages. Some fault diagnosis approaches can be found in the literature, where mathematical and control theory models are taken into account. However, in complex processes not all their characteristics are always known exactly, so mathematical modelling of processes is an extremely difficult task. Fault diagnosis can therefore be based mainly on data or heuristic information. The inherent characteristics of fuzzy logic theory make it suitable for processing this type of information, which is why it will be used to model processes and diagnose faults in a marine equipment valve. The fault diagnosis architecture proposed in this paper is based on analysing the discrepancy signals obtained between the outputs of the fuzzy models and the process data under study. These discrepancies, the residuals, are indicative of equipment fault. The proposed fault diagnosis architecture uses an intelligent decision-making approach to indicate the occurrence of faults. In this paper, this architecture will be used to diagnose abrupt faults in a marine equipment valve.
- Smart Structures and Materials Selected Papers from the 7th ECCOMAS Thematic Conference on Smart Structures and MaterialsPublication . Araújo, Aurélio L.; Soares, Carlos A. MotaThis work was compiled with expanded and reviewed contributions from the 7th ECCOMAS Thematic Conference on Smart Structures and Materials, that was held from 3 to 6 June 2015 at Ponta Delgada, Azores, Portugal. The Conference provided a comprehensive forum for discussing the current state of the art in the field as well as generating inspiration for future ideas specifically on a multidisciplinary level. The scope of the Conference included topics related to the following areas: Fundamentals of smart materials and structures; Modeling/formulation and characterization of smart actuators, sensors and smart material systems; Trends and developments in diverse areas such as material science including composite materials, intelligent hydrogels, interfacial phenomena, phase boundaries and boundary layers of phase boundaries, control, micro- and nano-systems, electronics, etc. to be considered for smart systems; Comparative evaluation of different smart actuators and sensors; Analysis of structural concepts and designs in terms of their adaptability to smart technologies; Design and development of smart structures and systems; Biomimetic phenomena and their inspiration in engineering; Fabrication and testing of smart structures and systems; Applications of smart materials, structures and related technology; Smart robots; Morphing wings and smart aircrafts; Artificial muscles and biomedical applications; Smart structures in mechatronics; and Energy harvesting.
- Design of an Underactuated USV CatamaranPublication . Assunção, Mário; Teodoro, Pedro; Marat-Mendes, Rosa; Franco, VictorThe Sea2Future program was developed at ENIDH, since 2018, and it has involved the construction of an unmanned surface vehicle (USV) with the participation of students and teachers of this educational institution. This firstUSV, with two hulls, referred to as USV-enautica1, included a control system which allows it to carry out several functions autonomously and it was used to study the composite construction, the propulsion command and control architectures, the navigation algorithms, and the control systems. The challenge of designing a lightweight hull suitable for coastal and open ocean navigation is described and the implemented solution for the microcontroller and software operation, the sensors, the navigation, and the control systems are explained. The USV has successfully demonstrated its ability to be operated remotely, which is necessary to validate the hydrodynamic parameters, and afterwards the aim of autonomous operation.
- Risk Driven Semantic Interoperability in the Maritime Surveillance DomainPublication . Marques, Fernando Sérgio Bryton Dias; Martínez, Jesús; Delgado, Olga; Arriaga, GonzaloSemantic Interoperability (SI) is essential for organizations as to share information, via computer systems, without which their efficiency and effectiveness is hampered. Assuming multiple actions for enhancing SI are possible, and that resources are usually scarce, the more relevant ones should have higher priority. Since information sharing, in the maritime surveillance domain, is essential for dealing with risks, such as irregular migration or piracy, this paper presents a method for prioritizing SI development actions based on the risks they aim to address. The method was developed by following the Design Science Research strategy, is based on the Delphi method and the Weighted Sum Model, and was validated in a real environment, with six organizations involved in maritime surveillance. The method aims to foster information sharing by supporting the development of action plans for enhancing SI, which may deliver relevant results faster, cheaper and less risky than traditional approaches.
- Data Based Modeling of a Large Scale Water Delivery SystemPublication . Fernandes, Marta; Oliveira, Paulo; Vieira, Susana; Mendonça, Luís; Nabais, João Lemos; Botto, Miguel AyalaWater is a vital resource and the growing populations and economies around the globe are pushing its demand worldwide. Therefore, the water conveyance operation should be well managed and improved. This paper proposes the development of reliable models able to predict water levels of a real 24.4 km water delivery channel in real time. This is a difficult task because this is a time-delayed dynamical system distributed over a long distance with nonlinear characteristics and external perturbations. Artificial neural networks are used, which are a well-known modeling technique that has been applied to complex and nonlinear systems. Real data is used for the design and validation of the models. The model obtained has the ability to predict water levels along the channel with minimum error, which can result in significant reduction of wasted water when implementing an automatic controller.
- Ensemble fuzzy models in personalized medicine: Application to vasopressors administrationPublication . Salgado, Cátia M.; Vieira, Susana M.; Mendonça, Luís; Finkelstein, Stan; Sousa, João M.C.Vasopressors administration in intensive care units is a risky surgical procedure that can be associated with infections, especially if done urgently such as in the case of unexpected systemic shock. The early prediction of a patient׳s transition to vasopressor dependence could improve overall outcomes associated with the procedure. Personalized medicine in the ICU encompasses the customization of healthcare on the level of individual patients, with diagnostic tests, monitoring interventions and treatments being fitted to the individual rather than the “average” patient. In this scope, this paper proposes an ensemble fuzzy modeling approach to a classification problem based on subgroups of patients identified by individual characteristics. A fuzzy c-means clustering algorithm was implemented to find subgroups of patients and each subgroup was used to develop a fuzzy model. The final classification of the ensemble fuzzy approach is obtained using two output selection criteria: an a priori decision criterion based on the distance from the cluster centers to the patients׳ characteristics, and an a posteriori decision criterion based on the uncertainty of the model output. The performance of the proposed approach is investigated using a real world clinical database and nine benchmark datasets. The ensemble fuzzy model approach performs better than the single model for the prediction of vasopressors administration in the ICU, being the a posteriori approach the best performer, with an average AUC of 0.85, showing this way the advantage of a personalized approach for patient care in the ICU.