2015
Autores
Furlan, M; Almada Lobo, B; Santos, M; Morabito, R;
Publicação
COMPUTERS & OPERATIONS RESEARCH
Abstract
This paper addresses the lot-sizing and scheduling problem of pulp and paper mills involving multiple paper machines. The underlying multi-stage integrated production process considers the following critical units: continuous digester, intermediate stocks of pulp and liquor, multiple paper machines and a recovery line to treat by-products. This work presents a mixed integer programming (MIP) model to represent the problem, as well as a solution approach based on a customized genetic algorithm (GA) with an embedded residual linear programming model. Some GA tools are explored, including literature and new operators, a novel diversification process and other features. In particular, the diversification process uses a new allele frequency measure to change between diversification and intensification procedures. Computational results show the effectiveness of the method to solve relatively large instances of the single paper machine problem when compared to other single paper machine solution methods found in the literature. For multiple paper machine settings, in most runs the GA solutions are better than those obtained for the MIP model using an optimization software.
2015
Autores
Gonçalves, S; Carneiro, D; Fdez-Riverola, F; Novais, P;
Publicação
EDMETIC
Abstract
The evaluation is a determining factor in developing successful strategies for learning. In a classroom context, the teacher can observe the behavior of students and identify different ways to facilitate the assessment without inducing stress, avoiding the negative consequences of this on the result of learning. However, in learning environments eLearning direct contact is impossible and, therefore, there should be alternative ways to provide both detection and prevention of stress during the evaluation. It is therefore appropriate stress analysis and identification of strategies for solving problems arising from its appearance. In this work, a stress analysis module for use is proposed for the online student assessment, which is capable of indicating to the teaching moments more propitious time to intervene and the contents that cause greater difficulties. In this way, the teacher can effectively assist students who need it most.
2015
Autores
Osório, A;
Publicação
Operations Research Letters
Abstract
In the present paper we characterize the optimal use of Poisson signals to establish incentives in the "bad" and "good" news models of Abreu et al. (1991). In the former, for small time intervals the signals' quality is high and we observe a "selective" use of information; otherwise there is a "mass" use. In the latter, for small time intervals the signals' quality is low and we observe a "fine" use of information; otherwise there is a "non-selective" use.
2015
Autores
Oliveira, PM; Vrancic, D; Freire, HF;
Publicação
CONTROLO'2014 - PROCEEDINGS OF THE 11TH PORTUGUESE CONFERENCE ON AUTOMATIC CONTROL
Abstract
A dual mode control configuration involving open-loop feedforward control to deal with set-point tracking and proportional integrative and derivative control to deal with disturbance rejection is proposed. The feedforward controller is a Posicast pre-filter shaping the reference input using either two or three steps. The switching between the open-loop and closed-loop control is performed automatically. The particle swarm optimization algorithm is deployed as design tool both for the feedforward and PID controller. Simulation results are presented showing the merits of the proposed technique.
2015
Autores
Mohanty, SR; Kishor, N; Ray, PK; Catalao, J;
Publicação
2015 IEEE POWER & ENERGY SOCIETY GENERAL MEETING
Abstract
2015
Autores
Pereira, J; Alves, J; Matos, M;
Publicação
2015 18TH INTERNATIONAL CONFERENCE ON INTELLIGENT SYSTEM APPLICATION TO POWER SYSTEMS (ISAP)
Abstract
This paper presents a new and efficient methodology for voltage control and network reconfiguration of distribution networks using fuzzy rules, EPSO and graph theory. A simpler representation of the network is built through a graph, were all the network loops are identified, both closed and open loops. This information is incorporated into the EPSO operators to create feasible solutions for the topological problem, avoiding convergence problems and reducing the computational burden. The initial EPSO population is created from the initial feasible solution, using appropriated heuristics to create feasible and possibly better initial solutions. At the same time a heuristic based strategy is used to perform local voltage control actions. Finally a fuzzy inference based algorithm is employed to achieve the optimal transformer and capacitor bank tap position. The proposed methodology was tested in a 13-bus test system, and in a real distribution system with 3200 buses.
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