INESCC-DL - Artigos em Revistas Internacionais
URI permanente para esta coleção:
Navegar
Percorrer INESCC-DL - Artigos em Revistas Internacionais por data de Publicação
A mostrar 1 - 10 de 30
Resultados por página
Opções de ordenação
- Using SSM to rethink the analysis of energy efficiency initiativesPublication . Neves, Luís Miguel Pires; Martins, António Gomes; Antunes, Carlos Alberto Henggeler; Dias, Luís Miguel CândidoThis paper reflects an attempt to rethink the process of analysis of energy efficiency initiatives using soft systems methodology (SSM) as a problem structuring tool. The aim of the work is to provide public and private initiative promoters or evaluators with a structured support for a more informed decision regarding the implementation of energy efficiency measures. The SSM approach contributed with the identification of all market players and their relations, as well as the insight into the deficiencies of current methodologies. Some future work directions are also proposed.
- A multi-criteria decision approach to sorting actions for promoting energy efficiencyPublication . Neves, Luís Miguel Pires; Martins, António Gomes; Antunes, Carlos Alberto Henggeler; Dias, Luís Miguel CândidoThis paper proposes a multi-criteria decision approach for sorting energy efficiency initiatives, promoted by electric utilities, with or without public funds authorized by a regulator, or promoted by an independent energy agency, overcoming the limitations and drawbacks of Cost-Benefit Analysis. The proposed approach is based on the ELECTRE-TRI multi-criteria method and allows the consideration of different kinds of impacts, although avoiding difficult measurements and unit conversions. The decision is based on all the significant effects of the initiative, both positive and negative ones, including ancillary effects often forgotten in cost-benefit analysis. The ELECTRE-TRI, as most multi-criteria methods, provides to the Decision Maker the ability of controlling the relevance each impact can have on the final decision in a transparent way. The decision support process encompasses a robustness analysis, which, together with a good documentation of the parameters supplied into the model, should support sound decisions. The models were tested with a set of real-world initiatives and compared with possible decisions based on Cost-Benefit analysis.
- Predictable impact of lighting control on the energy consumption of a building through computational simulationPublication . Bernardo, H.; Leitão, S.; Neves, L.; Amaral, P.; Bernardo, Hermano; Pires Neves, LuísBuilding energy simulation tools provide accurate predictions of the energetic performance of buildings and thermal comfort of its occupants, allowing an evaluation of the impact of proposed improvement measures, in order to support choice for the more economically viable. This paper aims at determining the energy saving potential that can be obtained by adequate measures and investments. It presents the simulated values of the impact on the energy consumptions of a building, caused by artificial lighting control systems set to maximize use of natural lighting. Results show that optimization measures have a significant impact on energy consumptions reduction, and lead to important economical savings.
- Simulation of the effect of voltage transients on an induction motor with ATP/EMTPPublication . Gonçalves, José; Baptista, José; Pires Neves, Luís; Oliveira, Filipe TadeuThe present study aims at understanding the behaviour of the induction motor when subject to different kinds of disturbances. The intention was to broaden the study of some disturbances by using a transient simulation software, ATP/EMTP, and comparing results with laboratory measurements. Obtained simulation results approached very closely the laboratory measurements, with small differences probably due to the model simplifying assumptions and uncertainties associated to the model parameter estimation process. However, although this theoretical model presents a response very similar to the actual model, improvements could be made by better modelling of the mechanical load, and by using different kinds of dynamic loads. Also, the use of more accurate laboratory equipment, and namely, programmable power supplies could lead to more accurate comparisons and better learning.
- Rotating speed stability and mechanical vibration analysis of one-stage inertia flexible rotor driven by variable speed drivesPublication . Oliveira, Filipe Tadeu; Donsión, M.P.; Peláez, G.This paper poses some questions as to the adequacy of the widespread use of variable speed drives. It presents a comparison of different variable speed drives, by studying their output wave forms and applying them to a mechanical one stage inertia flexible rotor specially designed for this purpose. The comparison of the output of the variable speed drives used reveals significant differences between them, which affect the way the load is driven and the overall behaviour of the mechanical system. A comparison against a sine wave reference shows that even the best of the variable speed drives used is outperformed, since the “perfect” sine wave ensures constant rotating speed, thus minimizing vibrations along the mechanical shaft.
- The small world of efficient solutions: empirical evidence from the bi-objective {0,1}-knapsack problemPublication . Silva, Carlos Gomes da; Clímaco, João; Filho, Adiel AlmeidaThe small world phenomenon, Milgram (1967) has inspired the study of real networks such as cellular networks, telephone call networks, citation networks, power and neural networks, etc. The present work is about the study of the graphs produced by efficient solutions of the bi-objective {0,1}-knapsack problem. The experiments show that these graphs exhibit properties of small world networks. The importance of the supported and non-supported solutions in the entire efficient graph is investigated. The present research could be useful for developing more effective search strategies in both exact and approximate solution methods of {0,1} multi-objective combinatorial optimization problems.
- Structuring an MCDA model using SSM: A case study in energy efficiencyPublication . Neves, Luís Miguel Pires; Dias, Luís Miguel Cândido; Antunes, Carlos Alberto Henggeler; Martins, António GomesThis work presents the use of a problem structuring method, Soft Systems Methodology (SSM), to structure a Multi-Criteria Decision Analysis (MCDA) model, aimed at appraising energy efficiency initiatives. SSM was useful to help defining clearly the decision problem context and the main actors involved, as well as to unveil the relevant objectives for each stakeholder. Keeney’s Value Focused Thinking approach was then used to refine and structure the list of objectives according to the perspective of the main evaluators identified. In addition to describing this particular case study, this paper aims at providing some general guidelines on how SSM may facilitate the emergence of objectives for MCDA models.
- Dynamics parameters estimation of an asynchronous machine plus mechanical shaft set through orbit frequency response analysisPublication . Oliveira, F.; Donsión, M. P.; Peláez, G.This paper presents some of the results obtained upon the experimental study of the behaviour of a prototype mechanical shaft driven by an induction electric machine. The main focus of this paper will be on the mechanical response of the set, based on the measurement of a number of mechanical variables and its integration in well-known mechanical models, allowing a more accurate estimation of the actual parameters of the prototype machine. The results thus obtained can then be used to test the theoretical models, estimate mechanical parameters more accurately and generally increase knowledge on the mechanical response of the prototype set.
- A multi-objective genetic algorithm applied to autonomous underwater vehicles for sewage outfall plume dispersion observationsPublication . Moura, Ana; Rijo, Rui; Silva, Pedro; Crespo, SidónioThis work presents a multi-objective genetic algorithm to solve route planning problem for multiple autonomous underwater vehicles (AUVs) for interdisciplinary coastal research. AUVs are mobile unmanned platforms that carry their own energy and are able to move themselves in the water without intervention from an external operator. Using AUVs one can provide high-quality measurements of physical properties of effluent plumes in a very effective manner under real oceanic conditions. The AUV's route planning problem is a combinatorial optimization problem, where the vehicles must travel through a three-dimensional irregular space with all dimensions known. Therefore, minimization of the total travel distance while considering the maximum number of water samples is the main objective. Besides the AUV kinematics restrictions other considerations must be taken into account to the problem, like the ocean currents. The practical applications of this approach are the environmental monitoring missions which typically require the sampling of a volume of water with non-trivial geometry for which parallel line sweeping might be a costly solution. Some real-life test problems and related solutions are presented.
- Evaluation of soft possibilistic classifications with non-specificity uncertainty measuresPublication . Gonçalves, Luisa M. S.; Fonte, Cidália C.; Júlio, Eduardo N. B. S.; Caetano, MarioThe aim of this paper was to investigate the usefulness of non-specificity uncertainty measures to evaluate soft classifications of remote sensing images. In particular, we analysed whether these measures could be used to identify the difficulties found by the classifier and to estimate the classification accuracy. Two nonspecificity uncertainty measures were considered, the non-specificity measure (NSp) and the U-uncertainty measure, and their behaviour was analysed to evaluate which is the most appropriate for this application. To overcome the fact that these two measures have different ranges, a normalized version (Un) of the U-uncertainty measure was used. Both measures were applied to evaluate the uncertainty of a soft classification of a very high spatial resolution multispectral satellite image, performed with an object-oriented image analysis based on a fuzzy classification. The classification accuracy was evaluated using an error matrix and the user's and producer's accuracies were computed. Two uncertainty indexes are proposed for each measure, and the correlation between the information given by them and the user's and producer's accuracies was determined to assess the relationship and compatibility of both sources of information. The results show that there is a positive correlation between the information given by the uncertainty and accuracy indexes, but mainly between the uncertainty indexes and the user's accuracy, where the correlation achieved 77%. This study shows that uncertainty indexes may be used, along with the possibility distributions, as indicators of the classification performance, and may therefore be very useful tools.
- «
- 1 (current)
- 2
- 3
- »