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Publicações

Publicações por José Boaventura

2001

Optimal control of air temperature and carbon dioxide concentration in greenhouses

Autores
Cunha, JB; Oliveira, PBD; Cordeiro, M;

Publicação
PROCEEDINGS OF THE WORLD CONGRESS OF COMPUTERS IN AGRICULTURE AND NATURAL RESOURCES

Abstract
Technologies employed in greenhouse production systems have been developed considerably during the recent decades. These improvements have taken place in many different research areas, such as the development of new covering materials and actuating equipments, modeling of the plant physiological processes and greenhouse climate, new cultural techniques, among many other topics. Although, due to economic and environmental increasing requirements there is still a need to improve the tools used for greenhouse management. At the present this work is being addressed with the emphasis on the economic optimization of the production process. This approach implies to know the influence of climate factors on production, as well the establishment of a good interface between engineers, physiologists and biologists. This paper presents the methods that are being implemented and tested with the aim of improving the climate management of a greenhouse located in the UTAD-University campus.

2010

Particle swarm optimization with fractional-order velocity

Autores
Pires, EJS; Machado, JAT; Oliveira, PBD; Cunha, JB; Mendes, L;

Publicação
NONLINEAR DYNAMICS

Abstract
This paper proposes a novel method for controlling the convergence rate of a particle swarm optimization algorithm using fractional calculus (FC) concepts. The optimization is tested for several well-known functions and the relationship between the fractional order velocity and the convergence of the algorithm is observed. The FC demonstrates a potential for interpreting evolution of the algorithm and to control its convergence.

2000

Greenhouse adaptive climate control techniques to reduce energy demand

Autores
Cunha, JB; De Moura Oliveira, PB; Cordeiro, M;

Publicação
2000 ASAE Annual Intenational Meeting, Technical Papers: Engineering Solutions for a New Century

Abstract
An adaptive greenhouse climate controller was implemented to regulate the air temperature, humidity and carbon dioxide concentration, with the aim of achieving set-point accuracy and reduce energy consumption. An optimization algorithm, based on the minimization of a cost function, was used to tune a Proportional-Integral-Derivative controller. The cost function is computed over a future time horizon of one hour as a function of the errors between the predicted and desired outputs and the predicted energy demand. Since the controller must be able to predict the greenhouse climate, it was needed to employ recursive identification algorithms to estimate in real-time the parameters of the climate model. When compared with commercially available controllers, this adaptive controller proved to have better performance regarding set-point accuracy and energy consumption.

2001

Solar radiation prediction methods applied to improve greenhouse climate control

Autores
Coelho, JP; Cunha, JB; Oliveira, PBD;

Publicação
PROCEEDINGS OF THE WORLD CONGRESS OF COMPUTERS IN AGRICULTURE AND NATURAL RESOURCES

Abstract
In this paper, deterministic and Artificial Neural Networks (ANNs) based techniques are applied to generate solar radiation forecasts with the purpose of being incorporated within a greenhouse predictive control strategy. These predictions are essential to estimate heat load fluctuations in the greenhouse caused by high frequency solar radiation changes, and so to improve ventilation and heating computation requirements for the greenhouse.

2011

ICT management in the agro-industry

Autores
Canuto, SA; Goncalves, RMRM; Neto, MM; Dos Santos Branco, FA; Cunha, JB;

Publicação
Proceedings of the 6th Iberian Conference on Information Systems and Technologies, CISTI 2011

Abstract
Human pressure is pushing many of our natural resources to their limits in various regions of the world. Optimize their use is an urgent need. The management of agro-industry has been aware of that need, seeking to improve the productivity and reduce waste throughout the production process, as well by increasing the distribution efficiency of their products. Information and Communication Technologies (ICT) can support the control/management of the process inputs and outputs in various activities. This article attempts to describe a complete mushroom production chain. The information system developed by the agro-industry company studied allows to acquire, in real-time, the information about what is being produced (quantity and type of mushroom), which products are to be delivered to the different clients and which should be the planning for the next few days. © 2011 AISTI.

2006

Fractional order electrical impedance of fruits and vegetables

Autores
Jesus, IS; Machado, JAT; Cunha, JB; Silva, MF;

Publicação
Proceedings of the 25th IASTED International Conference on Modelling, Identification, and Control

Abstract
The idea of fractional calculus is not new. Fractional derivatives are almost as old as integer-order definition. In 1695 Leibniz discussed this problem with L'Hospital, but many other contributions are due to investigators such as Liouville, Abel, Heaviside and Riemann, that formalized the theory of the non-integer order systems. The area of fractional calculus has primarily been the domain of mathematicians, and only had the theoretical foundation. Nowadays, this concept is employed in physics, engineering, biology, economy and other scientific fields. In our work, we apply the concepts of fractional calculus and the theory of electrical impedance to botanical elements. The fractional order behaviour of these type of systems are studied and the relation with the electrical impedance is formulated.

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