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Publicações

2015

A conjectural supply function equilibrium in energy and reserve for a weekly horizon

Autores
González, P; Villar, J; Díaz, C; Campos, FA;

Publicação
International Conference on the European Energy Market, EEM

Abstract
Despite the fact that reserves still have a small impact on the final electricity price, the rapid irruption of renewable and interruptible technologies has put in the spotlight the value of these services. It seems therefore important to rely on market models able to output realistic energy and reserve prices under imperfect competition. However, few are the authors that have modeled strategic behavior in both commodities. This paper presents an hourly multi-period oligopolistic model for energy and reserve markets, with units' commitment decisions and hydro-coordination, based on the conjectural supply function equilibrium. Its outputs have been compared with real Spanish data from the first weeks of 2011 with satisfactory results. © 2015 IEEE.

2015

Routing Protocols for IEEE 802.11-Based Mesh Networks

Autores
Sampaio, S; Vasques, F;

Publicação
- Encyclopedia of Information Science and Technology, Third Edition

Abstract

2015

An evolutionary multi-objective optimization system for earthworks

Autores
Parente, M; Cortez, P; Gomes Correia, AG;

Publicação
EXPERT SYSTEMS WITH APPLICATIONS

Abstract
Earthworks involve the leveling or shaping of a target area through the moving or processing of the ground surface. Most construction projects require earthworks, which are heavily dependent on mechanical equipment (e.g., excavators, trucks and compactors). Often, earthworks are the most costly and time-consuming component of infrastructure constructions (e.g., road, railway and airports) and current pressure for higher productivity and safety highlights the need to optimize earthworks, which is a non-trivial task. Most previous attempts at tackling this problem focus on single-objective optimization of partial processes or aspects of earthworks, overlooking the advantages of a multi-objective and global optimization. This work describes a novel optimization system based on an evolutionary multi-objective approach, capable of globally optimizing several objectives simultaneously and dynamically. The proposed system views an earthwork construction as a production line, where the goal is to optimize resources under two crucial criteria (costs and duration) and focus the evolutionary search (non-dominated sorting genetic algorithm-II) on compaction allocation, using linear programming to distribute the remaining equipment (e.g., excavators). Several experiments were held using real-world data from a Portuguese construction site, showing that the proposed system is quite competitive when compared with current manual earthwork equipment allocation.

2015

Dynamic inference of social roles in information cascades

Autores
Choobdar, S; Ribeiro, P; Parthasarathy, S; Silva, F;

Publicação
DATA MINING AND KNOWLEDGE DISCOVERY

Abstract
Nodes in complex networks inherently represent different kinds of functional or organizational roles. In the dynamic process of an information cascade, users play different roles in spreading the information: some act as seeds to initiate the process, some limit the propagation and others are in-between. Understanding the roles of users is crucial in modeling the cascades. Previous research mainly focuses on modeling users behavior based upon the dynamic exchange of information with neighbors. We argue however that the structural patterns in the neighborhood of nodes may already contain enough information to infer users' roles, independently from the information flow in itself. To approach this possibility, we examine how network characteristics of users affect their actions in the cascade. We also advocate that temporal information is very important. With this in mind, we propose an unsupervised methodology based on ensemble clustering to classify users into their social roles in a network, using not only their current topological positions, but also considering their history over time. Our experiments on two social networks, Flickr and Digg, show that topological metrics indeed possess discriminatory power and that different structural patterns correspond to different parts in the process. We observe that user commitment in the neighborhood affects considerably the influence score of users. In addition, we discover that the cohesion of neighborhood is important in the blocking behavior of users. With this we can construct topological fingerprints that can help us in identifying social roles, based solely on structural social ties, and independently from nodes activity and how information flows.

2015

Lung Function Classification of Smartphone Recordings - Comparison of Signal Processing and Machine Learning Combination Sets

Autores
Teixeira, JF; Teixeira, LF; Fonseca, J; Queirós Jacinto, TA;

Publicação
HEALTHINF

Abstract
Worldwide, over 250 million people are affected by chronic lung conditions such as Asthma and COPD. These can cause breathlessness, a harsh decrease in quality of life and, if not detected and duly managed, even death. In this paper, we aim to find the best and most efficient combination of signal processing and machine learning approaches to produce a smartphone application that could accurately classify lung function, using microphone recordings as the only input. A total of 61 patients performed the forced expiration maneuver providing a dataset of 101 recordings. The signal processing comparison experiments were conducted in a backward selection approach, reducing from 54 to 12 final envelopes, per recording. The classification experiments focused first on differentiating Normal from Abnormal lung function, and second in multiple lung function patterns. The results from this project encourage further development of the system.

2015

Exploiting DHT's Properties to Improve the Scalability of Mesh Networks

Autores
Sampaio, S; Vasques, F;

Publicação
- Encyclopedia of Information Science and Technology, Third Edition

Abstract

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