Cookies
O website necessita de alguns cookies e outros recursos semelhantes para funcionar. Caso o permita, o INESC TEC irá utilizar cookies para recolher dados sobre as suas visitas, contribuindo, assim, para estatísticas agregadas que permitem melhorar o nosso serviço. Ver mais
Aceitar Rejeitar
  • Menu
Publicações

2012

Optimum load management strategy for wind/diesel/battery hybrid power systems

Autores
Lujano Rojas, JM; Monteiro, C; Dufo Lopez, R; Bernal Agustin, JL;

Publicação
RENEWABLE ENERGY

Abstract
This paper discusses a novel load management strategy for the optimal use of renewable energy in systems with wind turbines, a battery bank, and a diesel generator. Using predictions concerning wind speed and power, controllable loads are used to minimize the energy supplied by the diesel generator and battery bank, subject to constraints imposed by the user's behavior and duty cycle of the appliances. We analyzed a small hybrid power system in Zaragoza, Spain, and the results showed load management strategy allowed improvement in the wind power use by shifting controllable loads to wind power peaks, increasing the state of the charge in the battery bank, and reducing the diesel generator operating time, when compared to a case without load management.

2012

Impact of Phase-shift Modulation on the Performance of a Single-stage Bidirectional Electric Vehicle Charger

Autores
Varajao, D; Araujo, RE; Moreira, C; Lopes, JP;

Publicação
38TH ANNUAL CONFERENCE ON IEEE INDUSTRIAL ELECTRONICS SOCIETY (IECON 2012)

Abstract
The Smart Vehicle-to-Grid Project at INESC TEC is currently studying the application of matrix converters to implement an isolated bidirectional AC-DC power converter using a single power conversion stage to provide a high-frequency link between the grid and vehicle. The single-stage structure and bidirectional power flow make the matrix converter an attractive solution for the charging applications of electric vehicles. A very brief overview of the matrix converter and its modulation strategy is presented, followed by detailed analysis. The power conversion system performance is investigated in terms of the switching commutation, input filter and input power factor. Simulations and experimental results of a prototype are also presented to further validate the proposed topology and operating principle.

2012

E-BUSINESS MATURITY: CONSTRAINTS ASSOCIATED WITH THEIR EVOLUTION

Autores
Morais, EP; Pires, JA; Goncalves, RM;

Publicação
JOURNAL OF ORGANIZATIONAL COMPUTING AND ELECTRONIC COMMERCE

Abstract
To compete effectively in the e-business world, an organization must structurally transform its internal foundation. This structural change requires an organization to develop an innovative e-business strategy, focusing on speed to market and breakthrough execution. Despite the recognition and care that in recent years has been dedicated to e-business, there remains a need for continuing research efforts that seek to better understand constraints on the evolution of an organization to a state that can take advantage of e-business possibilities. There is a special need for this when considering small and medium enterprises, or businesses in developing countries. To minimize risk exposure from e-business initiatives, it is imperative for an organization to identify potential constraints on e-business evolution. In this setting, we develop a research model that involves e-business constraints and e-business maturity. We classify the constraints into the categories of environment constraints, organizational constraints, and technological constraints. Our results indicate that there are constraints that can be more or less problematic, depending on the stage of maturity. The results are also quite different in large organizations versus Small and Medium Enterprises.

2012

Identifying Relationships in Transactional Data

Autores
Rodrigues, M; Gama, J; Ferreira, CA;

Publicação
ADVANCES IN ARTIFICIAL INTELLIGENCE - IBERAMIA 2012

Abstract
Association rules is the traditional way used to study market basket or transactional data. One drawback of this analysis is the huge number of rules generated. As a complement to association rules, Association Rules Network (ARN), based on Social Network Analysis (SNA) has been proposed by several researchers. In this work we study a real market basket analysis problem, available in a Belgian supermarket, using ARNs. We learn ARNs by considering the relationships between items that appear more often in the consequent of the association rules. Moreover, we propose a more compact variant of ARNs: the Maximal Itemsets Social Network. In order to assess the quality of these structures, we compute SNA based metrics, like weighted degree and utility of community.

2012

Multipliers with Transparent a-GIZO TFTs using a Neural Model

Autores
Bahubalindruni, G; Duarte, C; Tavares, VG; Barquinha, P; Martins, R; Fortunato, E; de Oliveira, PG;

Publicação
2012 20TH TELECOMMUNICATIONS FORUM (TELFOR)

Abstract
This paper presents the results of a preliminary study to examine the ability of post-silicon devices for analog processing. It is focused on the latest thin-film transistors (TFTs) with amorphous gallium-indium-zinc oxide (a-GIZO) as active layer. Three circuit configurations are presented: a differential pair and two multiplier topologies. Both triode and saturation regions of operation are included in the analysis, with the devices set to remain in strong accumulation. A neural model, which is developed based on the measured data of the TFTs, is used for the circuit simulations in the Cadence Virtuoso environment. The analog multipliers simulation results are compared against the expected functional results.

2012

Input-output control order release mechanism in a job-shop: How workload control improves manufacturing operations

Autores
Do Rosario Alves Moreira, M; Alves, RAFA;

Publicação
International Journal of Computational Science and Engineering

Abstract
This paper presents and evaluates an order release decision rule in a job-shop, based on the input-output control concept. The order release mechanism is part of a global decision-making scheme that includes four main decisions: accept/reject orders, define the order's due date, release the accepted jobs and dispatch it on the shop floor. This paper also presents an evaluation of two acceptance rules, four release mechanisms, and two dispatching rules, using four levels of due date tightness. Extensive simulation experiments were performed to compare the different decision rules, using several criteria: mean tardiness, percent tardy, mean absolute deviation, mean queue time in the shop floor and in the system, and machine usage. We conclude that considering the four decisions simultaneously improve the job-shop performance, and planning both the input and the output when deciding to release a job, leads to an improvement of the operational performance measures. Copyright © 2012 Inderscience Enterprises Ltd.

  • 3464
  • 4493