2015
Autores
Saez, C; Rodrigues, P; Gama, J; Robles, M; Garcia Gomez, JM;
Publicação
DATA MINING AND KNOWLEDGE DISCOVERY
Abstract
Knowledge discovery on biomedical data can be based on on-line, data-stream analyses, or using retrospective, timestamped, off-line datasets. In both cases, changes in the processes that generate data or in their quality features through time may hinder either the knowledge discovery process or the generalization of past knowledge. These problems can be seen as a lack of data temporal stability. This work establishes the temporal stability as a data quality dimension and proposes new methods for its assessment based on a probabilistic framework. Concretely, methods are proposed for (1) monitoring changes, and (2) characterizing changes, trends and detecting temporal subgroups. First, a probabilistic change detection algorithm is proposed based on the Statistical Process Control of the posterior Beta distribution of the Jensen-Shannon distance, with a memoryless forgetting mechanism. This algorithm (PDF-SPC) classifies the degree of current change in three states: In-Control, Warning, and Out-of-Control. Second, a novel method is proposed to visualize and characterize the temporal changes of data based on the projection of a non-parametric information-geometric statistical manifold of time windows. This projection facilitates the exploration of temporal trends using the proposed IGT-plot and, by means of unsupervised learning methods, discovering conceptually-related temporal subgroups. Methods are evaluated using real and simulated data based on the National Hospital Discharge Survey (NHDS) dataset.
2015
Autores
Ferreira, AP; Vaz, CB;
Publicação
2015 INTERNATIONAL CONFERENCE ON CLEAN ELECTRICAL POWER (ICCEP)
Abstract
This paper intends to give some insights on the performance comparison of two main conversion system technologies from a set of wind farms from two major promoters in the Portuguese wind energy sector. Conversion system technologies under analysis are based on the generator type, synchronous and asynchronous, which are the basis of the dominant technological trends in actual market. The performance assessment is accomplished using Data Envelopment Analysis (DEA) methodology, by computing the Malmquist index for group's comparison. From the obtained results, it is possible to conclude that farms with conversion systems based on synchronous generators have a better performance than the ones using conversion systems based on asynchronous generators. These conclusions may support the decision makers in repowering and overpowering processes.
2015
Autores
Osorio, GJ; Lujano Rojas, JM; Shafie khah, M; Matias, JCO; Catalao, JPS;
Publicação
2015 IEEE POWER & ENERGY SOCIETY GENERAL MEETING
Abstract
The constant increment in the penetration of renewable energy sources requires the improvement of the flexibility of the power system. Due to its high generation cost, it is expected that insular power systems experience an important increment in the power generation from renewable energy sources and, under this perspective, an energy storage system (ESS) could be the key factor to meet this goal. For these reasons, new approaches are necessary to optimize the scheduling of insular power systems, considering the specific characteristics of available ESSs. In this paper, a new approach that enables to fully incorporate the characteristics of a determined battery energy storage system (BESS) is proposed. The effectiveness of the proposed approach is illustrated by using a vanadium redox battery (VRB) in the analysis of an insular power system with renewable energy sources.
2015
Autores
Costa, PM; Galvao, T; Falcao e Cunha, JFE; Pitt, J;
Publicação
2015 8TH INTERNATIONAL CONFERENCE ON HUMAN SYSTEM INTERACTIONS (HSI)
Abstract
In recent years, the significant advancements in miniaturised computing and pervasive communication networks have paved the way for ubiquitous computing environments. In such environments users interact with systems through novel and implicit methods. In this context, affective computing provides a dimension of interaction, raising a number of opportunities to address not only utilitarian but also hedonic needs. At the same time, a number of challenges arise beyond the technical aspects, that are related to the individual and other societal implications. A review of the main opportunities and challenges is presented, supporting the identification of the main requirements for the design and development of systems in interactive pervasive environments, focusing on an affective loop of interaction. A framework is proposed, identifying main modules and functionality alongside a methodology to instantiate in specific domains of application.
2015
Autores
Pinto, T; Silva, H; Vale, ZA; Santos, G; Praça, I;
Publicação
26th International Workshop on Database and Expert Systems Applications, DEXA 2015, Valencia, Spain, September 1-4, 2015
Abstract
2015
Autores
Rocha, A; Correia, AM; Costanzo, S; Reis, LP;
Publicação
Advances in Intelligent Systems and Computing
Abstract
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