Repositório Comunidade: Gestão IndustrialGestão Industrialhttp://hdl.handle.net/10198/1602016-02-08T14:20:48Z2016-02-08T14:20:48ZEfficiency assessment of wind farms: a two-stage approachVaz, Clara B.Ferreira, Ângela P.http://hdl.handle.net/10198/118912015-07-27T09:30:21Z2015-01-01T00:00:00ZTítulo: Efficiency assessment of wind farms: a two-stage approach
Autor: Vaz, Clara B.; Ferreira, Ângela P.
Resumo: This study proposes an integrated methodology to provide insights regarding the efficiency of wind farms of two
major promoters in the Portuguese energy sector. The focus of the wind farms performance assessment is on the operating
stage which corresponds to the electrical energy production process. In a first stage, Data Envelopment Analysis is used to
measure the efficiency of wind farms in producing electrical energy from the resources available and exogenous variables. This
method is complemented by bootstrapping to refine the efficiency estimates. In a second stage, the factors which may influence
the performance of wind farms are investigated by using truncated regression with bootstrapping. The methodology proposed
may be used by promoters in management of wind farms and may also be useful to regulator agents on the supervision of the
energy market.2015-01-01T00:00:00ZThe use of ore microscopydata for flotation process control by means of a liberation model: a case studyBarros, ElisaLeite, MárioCavalheiro, Abíliohttp://hdl.handle.net/10198/118522015-10-01T01:13:27Z2000-01-01T00:00:00ZTítulo: The use of ore microscopydata for flotation process control by means of a liberation model: a case study
Autor: Barros, Elisa; Leite, Mário; Cavalheiro, Abílio
Resumo: Any realistic description of ore processing dealing with a particulate system requires an adequate characterization of it properties, mainly particle size and grade,because these are the most important variables that influence the performance of a mineral processing separation, such as froth flotation. Experience has shown that an appropriate model for liberation of solid phases must always integrate all available mineralogical data by comminution. The present work aims too describe a case study for calibration of a liberation model with data obtained from semi-quantitative mineralogical analysis (ore microscopy). For the specific case of random comminution, a limit probability argument is used to justify the introduction of Euler's Beta Law as well-suited tool for describing the liberantion state of a comminuted ore, because it is able to predict the grade distribution of a given iso-size fraction of such particulate system.2000-01-01T00:00:00ZExact and heuristic approaches for lot splitting and scheduling on identical parallel machinesPimentel, CarinaAlvelos, Filipe PereiraDuarte, António J.S.T.Carvalho, J. M.Valério dehttp://hdl.handle.net/10198/112822015-10-01T01:21:53Z2011-01-01T00:00:00ZTítulo: Exact and heuristic approaches for lot splitting and scheduling on identical parallel machines
Autor: Pimentel, Carina; Alvelos, Filipe Pereira; Duarte, António J.S.T.; Carvalho, J. M.Valério de
Resumo: In this paper, we address a lot splitting and scheduling problem existent in a textile factory. The factory we study produces a set of products that are made of, or assembled from, a list of components. During production, each component can be split into one or several lots of different sizes and each lot will be produced independently on one of a group of identical parallel machines. We formulate the problem into a mixed integer programming model and develop a heuristic method to solve the model. The heuristic method is based on a network flow model with the objective to minimise the weighted sum of the total tardiness of products and the deviations occurred during production of each product. The deviation of a product is measured by the deviation of product completion time (the last component lot completion time) and completion time of the rest of components lots for the same product. We present computational results and performance measures of the network flow heuristic for a set of randomly generated instances based on real world data.2011-01-01T00:00:00ZWarehouse design and product assignment and allocation: a mathematical programming modelGeraldes, Carla A. S.Carvalho, SameiroPereira, Guilhermehttp://hdl.handle.net/10198/108022014-10-14T01:00:36Z2012-01-01T00:00:00ZTítulo: Warehouse design and product assignment and allocation: a mathematical programming model
Autor: Geraldes, Carla A. S.; Carvalho, Sameiro; Pereira, Guilherme
Resumo: Warehouses can be considered one of the most important nodes in supply chains. The dynamic nature of today’s markets compels organizations to an incessant reassessment in an effort to respond to continuous challenges. Therefore warehouses must be continually re-evaluated to ensure that they are consistent with both market’s demands and management’s strategies. In this paper we discuss a mathematical programming model aiming to support product assignment and allocation to the functional areas as well as the size of each area. In particular a large mixed-integer programming model (MILP) is presented to capture the trade-offs among the different warehouse costs in order to achieve global optimal design satisfying throughput requirements.2012-01-01T00:00:00Z