Time filter

Source Type

Rio Grande, Brazil

Camponogara E.,Federal University of Santa Catarina | Nazari L.F.,Instituto Federal Catarinense
Mathematical Problems in Engineering | Year: 2015

Piecewise-linear functions can approximate nonlinear and unknown functions for which only sample points are available. This paper presents a range of piecewise-linear models and algorithms to aid engineers to find an approximation that fits best their applications. The models include piecewise-linear functions with a fixed and maximum number of linear segments, lower and upper envelopes, strategies to ensure continuity, and a generalization of these models for stochastic functions whose data points are random variables. Derived from recursive formulations, the algorithms are applied to the approximation of the production function of gas-lifted oil wells. © 2015 Eduardo Camponogara and Luiz Fernando Nazari. Source

Caires E.F.,State University of Ponta Grossa | Garbuio F.J.,Instituto Federal Catarinense | Churka S.,University of Sao Paulo | Joris H.A.W.,Instituto Agronomico Of Campinas
Agronomy Journal | Year: 2011

Gypsum has been used in tropical and subtropical agriculture when subsoil acidity is an important yield-limiting factor. However, the conditions that promote increased crop yield as a result of gypsum addition in no-till (NT) systems still remain unclear. A field trial examined the effects of newly and previously surface-applied gypsum in a long-term NT system on the soil chemical properties and nutrition and yield of corn (Zea mays L.), wheat (Triticum aestivum L.), and soybean [Glycine max (L.) Merr.] on a clayey Rhodic Hapludox in Parana State, Brazil. Gypsum was surface-applied at 0 and 6 Mg ha -1 in 2004 on plots that had received gypsum previously at 0, 3, 6, and 9 Mg ha -1 in 1998. Surface-applied gypsum newly and previously improved exchangeable Ca and SO 4-S availability throughout the soil profi le, and increased the cumulative grain yield of the crops. Exchangeable K losses through leaching caused by gypsum application were low, and a larger mobility of exchangeable Mg as compared with exchangeable K in soil was found as a result of gypsum addition. An increase in Ca content in the corn, wheat, and soybean leaves, and in S content in the corn and wheat leaves occurred following the gypsum application. Th e use of gypsum showed economic viability to maximize crop grain production in a long-term NT soil with a sufficient level of exchangeable Ca (≥8 mmolc dm -3) and low levels of exchangeable Al (≤4 mmolc dm -3) and Al saturation (≤15%) in the subsoil layers (20-60 cm). © 2011 by the American Society of Agronomy. Source

Beltrame R.C.,Federal University of Santa Maria | Zientarski J.R.R.,Instituto Federal Catarinense | Da Silva Martins M.L.,Federal University of Technology of Parana | Pinheiro J.R.,Federal University of Santa Maria | Hey H.L.,Federal University of Santa Maria
IEEE Transactions on Power Electronics | Year: 2011

This paper proposes the concept and the synthesis methodology of simplified zero-voltage-transition (ZVT) circuits applied to bidirectional pulsewidth modulation poles. The main goal of simplified ZVT circuits is to make possible the use of conventional modulation schemes to accomplish better converter performance and to eliminate the synchronous-switching requirements imposed by ZVT integrated multipole topologies. To derive the simplified ZVT circuits, a synthesis methodology is proposed based on the generalization of the ZVT technique, where the restrictions to achieve the zero-voltage switching for the main converter switches are identified. Thereafter, a set of simplified semiconductor switches composed by only one high-frequency switch is defined to be used in the simplified ZVT auxiliary circuits. Thus, using the proposed synthesis methodology, any simplified ZVT topology can be derived, whether or not they have appeared in a previous publication. In order to validate the proposed approach, experimental results for a three-phase ZVT inverter, employing the minimum-loss space vector modulation and operating at 1.5 kW and 20 kHz are presented. The prototype presented an efficiency of 98% at full load representing an improvement of 0.5% when compared to its hard-switched counterpart and 1.8% when compared to an integrated ZVT topology. © 2006 IEEE. Source

Magalhaes D.A.,Instituto Federal Catarinense
Revista Brasileira de Ensino de Fisica | Year: 2014

The purpose of this paper is to present a pedagogical approach concerning climate change and global warming. We present some research institutes and the leading international body for the assessment of climate change and a brief overview of papers published on the subject in Brazilian journals, in Portuguese. We also discuss some elementary ideas, such as blackbody radiation and elementary models, greenhouse effect, radiative forcing and temperature anomalies. The subject is discussed in different conceptual and mathematical levels of teaching. © The Sociedade Brasileira de Física. Source

Caires E.F.,UEPG | Maschietto E.H.G.,UEPG | Garbuio F.J.,Instituto Federal Catarinense | Churka S.,University of Sao Paulo | Joris H.A.W.,UEPG
Scientia Agricola | Year: 2011

The conditions in which a favorable response to a gypsum application can be expected on crop yields are not clear. A 3-year field trial was carried out to evaluate the effects of gypsum application on soil chemical attributes and nutrition and yield of corn (Zea mays L.) and soybean (Glycine max L. Merrill) on a clayey Typic Hapludox of high fertility and low acidity under no-till in Guarapuava, Parana State, Brazil. Treatments were arranged in a randomized complete block design with four replications, and consisted of gypsum application on the soil surface at 4, 8, and 12 Mg ha-1. Gypsum application increased the P content in the soil most superficial layer (0.0 - 0.1 m) and also the exchangeable Ca and S-SO42- contents and the Ca/Mg ratio in the soil profile (0.0 - 0.6 m). Gypsum also caused leaching of Mg and K exchangeable in the soil. An increase in Ca concentrations in the corn leaves, and in P and S concentrations in the corn and soybean leaves occurred following the gypsum application. A yield response of corn to initial application of gypsum was found, but subsequent soybean crops did not respond. Gypsum application proved to be an effective practice to maximize no-till corn grain yield. Source

Discover hidden collaborations