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Publicações

2006

Parameterisation effect on the behaviour of a head-dependent hydro chain using a nonlinear model

Autores
Catalao, JPS; Mariano, SJPS; Mendes, VMF; Ferreira, LAFM;

Publicação
ELECTRIC POWER SYSTEMS RESEARCH

Abstract
This paper is on the problem of short-term hydro scheduling (STHS), particularly concerning a head-dependent hydro chain. We use a method based on nonlinear programming (NLP), namely quadratic programming, to consider hydroelectric power generation a function of water discharge and of the head. The method has been applied successfully to solve a test case based on a realistic cascaded hydro system with a negligible computational time requirement and is also applied to show that the role played by reservoirs in the hydro chain do not depend only on their relative position. As a new contribution to earlier studies, which presented reservoir operation rules mainly for medium and long-term planning procedures, we show that the physical data defining hydro chain parameters used in the nonlinear model have an effect on the STHS, implying different optimal storage trajectories for the reservoirs accordingly not only with their position in the hydro chain but also with the new parameterisation defining the data for the hydro system. Moreover, considering head dependency in the hydroelectric power generation, usually neglected for hydro plants with a large storage capacity, provides a better short-term management of the conversion of the potential energy available in the reservoirs into electric energy, which represents a major advantage for the hydroelectric utilities in a competitive electricity market.

2006

Design and development of new controller suitable to neighbourhood electric vehicle propulsion control

Autores
Soares, JR; Cerqueira, NM; Pinto de Castro, RP; Santos Oliveira, H; Esteves Araujo, R;

Publicação
IECON 2006 - 32ND ANNUAL CONFERENCE ON IEEE INDUSTRIAL ELECTRONICS, VOLS 1-11

Abstract
The purpose of this paper is to design the propulsion system for a Neighbourhood Electric Vehicle (NEV) and implement a control architecture which is suitable for this kind of application. The review of the vehicle model is presented. This model is used to establish the propulsion system requirements in terms of torque and power. Once these are known the specifications for the motor and transmission system are derived. A digital platform has been developed and implemented. This hardware platform interacts via wireless communication with a high level application to facilitate writing and reading the host registers. A PC graphical user interface was developed to allow the computation of the control parameters. Some experimental results are provided in order to verify the performance of this new controller.

2006

Local and global dominance conditions for the weighted earliness scheduling problem with no idle time

Autores
Valente, JMS;

Publicação
COMPUTERS & INDUSTRIAL ENGINEERING

Abstract
In this paper, we present dominance conditions for the single machine weighted earliness scheduling problem with no idle time. We also propose an algorithm that can be used to improve upper bounds for the weighted earliness criterion and lower bounds for an earliness/tardiness problem. The computational tests show that the algorithm is superior to an initial heuristic schedule and an existing adjacency condition.

2006

ODAC: Hierarchical Clustering of Time Series Data Streams

Autores
Rodrigues, PP; Gama, J; Pedroso, JP;

Publicação
PROCEEDINGS OF THE SIXTH SIAM INTERNATIONAL CONFERENCE ON DATA MINING

Abstract
This paper presents a time series whole clustering system that incrementally constructs a tree-like hierarchy of clusters, using a top-down strategy. The Online Divisive-Agglomerative Clustering (ODAC) system uses a correlation-based dissimilarity measure between time series over a data stream and possesses an agglomerative phase to enhance a dynamic behavior capable of concept drift detection. Main features include splitting and agglomerative criteria based on the diameters of existing clusters and supported by a. significance level. At each new example, only the leaves are updated, reducing computation of unneeded dissimilarities and speeding up the process every time the structure grows. Experimental results on artificial and real data suggest competitive performance on clustering time series and show that the system is equivalent to a batch divisive clustering on stationary time series, being also capable of dealing with concept drift. With this work, we assure the possibility and importance of hierarchical incremental time series whole clustering in the data stream paradigm, presenting a. valuable and usable option.

2006

A spatio-temporal database system based on TimeDB and Oracle Spatial

Autores
Carvalho, A; Ribeiro, C; Sousa, AA;

Publicação
Research and Practical Issues of Enterprise Information Systems

Abstract
The importance of the spatial component of data items has been long recognized and gave rise to a successful line of research and development in Geographic Information Systems (GIS). In many application domains it is also essential to deal with the evolution of data along time and to integrate spatial, temporal and other aspects of the information domain in an expressive and operationally effective manner. Until recently, temporal solutions provided by spatial database systems were semi-temporal approaches lacking full temporal support. As a consequence, most spatial database systems manage snapshots of the present state of facts without fully exploiting historical temporal aspects. This paper provides preliminary results on a spatiotemporal database implementation. The proposed system builds on existing database technologies, TimeDB and Oracle Spatial, for temporal and spatial support, respectively. The justification for the choice of these technologies is given, based on the state of the art in spatial and temporal database research. The integration of the spatial and temporal components is achieved with the extension of the TimeDB implementation layer. A set of goals has been established in order to cover both the integration of the spatial support and the enforcement of the temporal requirements in the extended system. Issues and solutions are presented and illustrative examples show the use of the implemented functionalities.

2006

Image Analysis and Recognition, Third International Conference, ICIAR 2006, Póvoa de Varzim, Portugal, September 18-20, 2006, Proceedings, Part I

Autores
Campilho, AC; Kamel, MS;

Publicação
ICIAR (1)

Abstract

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