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Maragogi, Brazil

Gomes Silva M.J.,IFAL | Silva Araujo C.,Federal University of Paraiba | Marques Bezerra S.T.,Federal University of Pernambuco | Rocha Souto C.,Federal University of Paraiba | And 2 more authors.
IEEE Latin America Transactions

This paper presents the project of an adaptive control system to modeling and controlling, in real time, a water distribution system. The controllers act in determining the turning speed of the motor/pump set and in the opening angle of control valves. An experimental workbench was set aiming at modeling and identifying parametrically a hydraulic network. The control system is a Generalized Minimum Variance self-tuning (GMV), whose parameters where real-time estimated by the recursive least squares (MQR) method according to the imposed inputs to the converter and the valves. The GMV aims at the pressure control in measuring points, which provided the reduction of energy and water in the workbench. Experimental results show the performance of adaptive control system and its ability to control the water distribution process. © 2003-2012 IEEE. Source

Oliveira L.C.,Federal University of Campina Grande | Melcher E.U.K.,Federal University of Campina Grande | Melcher E.U.K.,Center for Strategic Technologies | Thirstrup C.,Coloplast | And 3 more authors.
2012 IEEE I2MTC - International Instrumentation and Measurement Technology Conference, Proceedings

This paper presents a surface plasmon resonance (SPR) sensor system based on a polymer prism chip. The device allows operation in both, the angular (AIM) and wavelength (WIM) interrogation modes. The basic mathematical formulation for both operating modes is discussed. Experimental sensogrammes obtained for both modes with the same polymer prism chip, are presented and compared. The results illustrate the feasibility of the proposed solution. © 2012 IEEE. Source

Porto M.L.A.,Federal University of Vicosa | Alves J.C.,IFAL | de Souza A.P.,Federal University of Paraiba | Araujo R.C.,Federal University of Paraiba | And 2 more authors.
Horticultura Brasileira

Lettuce production in hydroponic system presents growing expansion in Brazil, but still there are problems of quality and risk of nitrate accumulation. This work was carried out to evaluate the lettuce production and nitrate accumulation in hydroponic system depending on the increasing levels of nitrogen in the nutrient solution. The experiment was conducted in greenhouse of the Universidade Federal da Paraíba, Brazil. The lettuce plants were grown in nutrient solution containing increasing levels of N (11, 13, 15, 17, 19 and 21 mmol L-1) during a 25-day period. An entirely randomized design with four replications was used. Plant total yield (PTT), plant commercial yield (PCM) and nitrate contents in the fresh matter of roots, stems and leaves of the lettuce were evaluated. There were no significant effects of increasing levels of N in nutrient solution on PTT and PCM, average values of 357.3 and 352.5 g/plant being observed, respectively. The increased levels of N in nutrient solution increased linearly nitrate content on all lettuce parts. The nitrate content reached 659, 623 and 615 mg/kg in the fresh matter of roots, stems and leaves, respectively, at the highest N level. Nevertheless, the maximum nitrate content observed in leaves was far below the risk level for human health. Source

Argolo C.,IFAL | Otaviano H.,IFAL | Gleria I.,Federal University of Alagoas | Arashiro E.,Federal University of Ouro Preto | Tome T.,University of Sao Paulo
International Journal of Bifurcation and Chaos

We investigate the critical behavior of a stochastic lattice model describing a predatorprey system. By means of Monte Carlo procedure we simulate the model defined on a regular square lattice and determine the threshold of species coexistence, that is, the critical phase boundaries related to the transition between an active state, where both species coexist and an absorbing state where one of the species is extinct. A finite size scaling analysis is employed to determine the order parameter, order parameter fluctuations, correlation length and the critical exponents. Our numerical results for the critical exponents agree with those of the directed percolation universality class. We also check the validity of the hyperscaling relation and present the data collapse curves. © 2010 World Scientific Publishing Company. Source

Porto M.L.A.,IFAL | Puiatti M.,Federal University of Vicosa | Fontes P.C.R.,Federal University of Vicosa | Cecon P.R.,Federal University of Vicosa | Alves J.C.,IFAL
Horticultura Brasileira

The importance of hybrid winter squash ("Tetsukabuto" type) is rising in Brazil, especially in Minas Gerais state, but few studies have been carried out in relation to fertilization. We evaluated yield and nitrate accumulation in fruits of hybrid winter squash ("Tetsukabuto" type) depending on the nitrogen fertilization in Viçosa, Minas Gerais state, Brazil. The randomized block experimental design was used, arranged in a 2×5 factorial design, with two nitrogen sources (ammonium sulphate and ammonium nitrate) and five nitrogen doses (0; 50; 100; 200 and 400 kg ha-1), and four replications. The number of fruits per plant, average fruit mass, fruit yield and nitrate accumulation in the fruits were evaluated. No significant effects of nitrogen sources and of the interaction between nitrogen sources and nitrogen doses was found on the productive characteristics of the hybrid winter squash, but these characteristics were increased depending on the N doses applied. The highest number of fruits/plant (6.9 units), highest average fruit mass (1.76 kg/fruit) and highest fruit yield (17.16 t ha-1) were obtained in the doses 339, 217 and 260 kg -1 of N, respectively. The rates of N for maximum economic efficiency were 251 and 238 kg ha-1, resulting in fruit yields of 17.15 and 17.07 t ha-1, for the ammonium sulfate and ammonium nitrate, respectively. Nitrate accumulation in fruits employing N doses in the form of ammonium sulfate was not verified. However, the nitrate content in the fruits presented lineal increment depending on the N doses in the form of ammonium nitrate. At the highest N rate, the nitrate content in the fruit fresh matter was 406 mg kg-1. However, this nitrate content value does not represent risk for human health. Source

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