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Publications

2007

A decision-support system based on particle swarm optimization for multiperiod hedging in electricity markets

Authors
Azevedo, F; Vale, ZA; de Moura Oliveira, PBD;

Publication
IEEE TRANSACTIONS ON POWER SYSTEMS

Abstract
This paper proposes a particle swarm optimization (PSO) approach to support electricity producers for multiperiod optimal contract allocation. The producer risk preference is stated by a utility function (U) expressing the tradeoff between the expectation and variance of the return. Variance estimation and expected return are based on a forecasted scenario interval determined by a price range forecasting model developed by the authors. A certain confidence level a is associated to each forecasted scenario interval. The proposed model makes use of contracts with physical (spot and forward) and financial (options) settlement. PSO performance was evaluated by comparing it with a genetic algorithm-based approach. This model can be used by producers in deregulated electricity markets but can easily be adapted to load serving entities and retailers. Moreover, it can easily be adapted to the use of other type of contracts.

2007

Exploiting a prioritized MAC protocol to efficiently compute min and max in multihop networks

Authors
Andersson, B; Pereira, N; Tovar, E;

Publication
PROCEEDINGS OF THE FIFTH WORKSHOP ON INTELLIGENT SOLUTIONS IN EMBEDDED SYSTEMS

Abstract
Consider a wireless sensor network (WSN) where a broadcast from a sensor node does not reach all sensor nodes in the network; such networks are often called multihop networks. Sensor nodes take sensor readings but individual sensor readings are not very important. It is important however to compute aggregated quantities of these sensor readings. The minimum and maximum of all sensor readings at an instant are often interesting because they indicate abnormal behavior for example if the maximum temperature is very high then it may be that afire has broken out. We propose an algorithm for computing the min or max of sensor reading in a multihop network. This algorithm has the particularly interesting property of having a time complexity that does not depend on the number of sensor nodes; only the network diameter and the range of the value domain of sensor readings matter

2007

Self-paternable amine-functionalised organic-inorganic hybrids for integrated optics substrates

Authors
Sa Ferreira, RA; Fu, LS; Macedo, AG; Silva, NJO; Vicente, C; Carlos, LD; Andre, PS; Nogueira, R; Pecorato, E; Ribeiro, SJL; De Zea Bermudez, V; Pellegrino, LP; Monteiro, P; Marques, PVS;

Publication
Materials Research Society Symposium Proceedings

Abstract

2007

Long-Range Dependence in Heart Rate Variability Data: ARFIMA Modelling vs Detrended Fluctuation Analysis

Authors
Leite, A; Rocha, AP; Silva, ME; Gouveia, S; Carvalho, J; Costa, O;

Publication
COMPUTERS IN CARDIOLOGY 2007, VOL 34

Abstract
Heart rate variability (HRV) data display non-stationary characteristics and exhibit long-range correlation (memory). Detrended fluctuation analysis (DFA) has become a widely-used technique for long memory estimation in non-stationary HRV data. Recently, we have proposed an alternative approach based on fractional integrated autoregressive moving average (ARFIMA) models. ARFIMA models, combined with selective adaptive segmentation may be used to capture and remove long-range correlation, leading to an improved description and interpretation of tire components in 24 hour HRV recordings. In this work estimation of long memory by DFA and selective adaptive ARFIMA modelling is carried out in 24 hour HRV recordings of 17 healthy subjects of two age groups. The two methods give similar information on long-range global characteristics. However ARFIMA modelling is advantageous, allowing the description of long-range correlation in reduced length segments.

2007

A new plant modelling approach for formal verification purposes

Authors
Machado, J; Seabra, E; Soares, F; Campos, J;

Publication
IFAC Proceedings Volumes (IFAC-PapersOnline)

Abstract
This paper presents a new approach in plant modeling for the formal verification of real time systems. A system composed by two tanks is used, where all its components are modeled by simple modules and all the interdependences of the system's modular models are presented. As innovating parameters in the plant modeling, having as purpose its use on formal verification tasks, the plant is modeled using Dymola software and Modelica programming language. The results obtained in simulation are used to define the plant models that are used for the formal verification tasks, using the model-checker UPPAAL. The paper presents, in a more detailed way, the part of this work that is related to formal verification, being pointing out the used plant modeling approach. © 2007 IFAC.

2007

Exploiting a prioritized MAC protocol to efficiently compute interpolations

Authors
Andersson, B; Pereira, N; Tovar, E;

Publication
ETFA 2007: 12TH IEEE INTERNATIONAL CONFERENCE ON EMERGING TECHNOLOGIES AND FACTORY AUTOMATION, VOLS 1-3

Abstract
Consider a network where all nodes share a single broadcast domain such as a wired broadcast network. Nodes take sensor readings but individual sensor readings are not the most important pieces of data in the system. Instead,, we are interested in aggregated quantities of the sensor readings such as minimum and maximum values, the number of nodes and the median among a set Of sensor readings on different nodes. In this paper we show that a prioritized medium access control (MAC) protocol may advantageously be exploited to efficiently compute aggregated quantities of sensor readings. In this context, we propose a distributed algorithm that has a very low time and message-complexity for computing certain aggregated quantities. Importantly we show that if every sensor node knows its geographical location, then. sensor data can be interpolated with our novel distributed algorithm, and the message-complexity of the algorithm is independent of the number of nodes. Such an interpolation of sensor data can be used to compute any desired function; for example the temperature gradient in a room (e.g., industrial plant) densely populated with sensor nodes, or the gas concentration gradient within a pipeline or traffic tunnel.

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