ABSTRACT The objective of this study was to develop artificial neural networks (ANNs) for predicting animal thermal comfort based on temperature and relative humidity of the air for each day of the year. The data on temperature and relative humidity for a 25-year historical series collected at the Padre Ricardo Remetter Conventional Meteorological Station, located in the city of Santo Antônio de Leverger - Mato Grosso (Brazil), were retrieved from the website of the National Institute of Meteorology. According to the day of the year, the temperature and humidity index was determined as a function of the climatic variables. Therefore, the day of the year was the input variable of the neural networks, and the temperature and humidity index (THI) was the output variable. The number of layers and neurons used for establishing different architectures was variable. Data were adjusted on the basis of mean square errors, performance and efficiency indexes, and normality tests. The values estimated by the networks and those obtained from the historical series did not differ significantly. The networks with the best performance were selected for graphical analysis of residuals. The ANNs developed in this study predicted animal thermal comfort with adequate reliability and precision.

ABSTRACT This study aimed to develop artificial neural networks for the estimation of tractor fuel consumption during soil preparation, according to the adopted system. The multilayer perceptron network was chosen. As input data: the soil mechanical penetration resistance, the mobilized area by implements, the working gear and the tractor engine speed. The number of layers and neurons varied to form different architectures. The adjustment was verified based on various statistical criteria. The values estimated by the networks did not differ significantly from those obtained experimentally. The conclusion was that the networks showed adequate reliability and accuracy to predicting the fuel consumption in each tillage system, in function of the input data and this can be a useful tool for planning and management of agricultural operations.

No presente estudo, foram elaborados modelos empíricos para determinar a força de tração demandada por arados de discos, escarificadores e semeadoras adubadoras, em função da resistência mecânica do solo à penetração. A média da referida resistência, determinou-se até as profundidades de 25; 35 e 15 cm, em correspondência com as regulagens do arado de discos, escarificador e semeadora adubadora. O ajuste foi verificado de acordo com o coeficiente de determinação, gráficos de dispersão, análise residual e teste t (Student). Com base nessas análises, confirmou-se a normalidade dos resíduos, e foram estabelecidos intervalos de confiança com 95% de probabilidade. Os valores estimados e obtidos experimentalmente não discreparam significativamente. Concluiu-se que as funções exponenciais associadas apresentaram adequada precisão e confiabilidade para predizer a força de tração, considerando-se a resistência mecânica do solo à penetração e que os modelos podem ser uma ferramenta útil para o planejamento e gestão de operações agrícolas mecanizadas em solos com textura similar às desta pesquisa.

In this study, empirical models were developed to determine the tensile force demanded by disc plows, harrows and planters fertilizers, as function of soil mechanical resistance to penetration. The mean of the referred resistance was determined until 25, 35 and 15 cm depths, according to the regulations for the disc plow, springs harrow and fertilizer seeder. The adjustment was verified based on the coefficient of determination, dispersion graphics, residual analysis and t test (Student). It was confirm the normality of the residuals and to establish intervals of confidence with 95% of probability. The estimated and experimentally obtained values did not differ significantly. It was concluded that the associated exponential functions presented appropriate precision and reliability to predict the traction force being considered the soil mechanical resistance to penetration and that the models can be a useful tool for planning and management of mechanized farming operations in soils with texture similar to those of this research.

O estudo das tensões em colhedoras de forragens é imprescindível, uma vez que as condições de operação são muito variáveis e severas. Utilizou-se um sistema "datalogger" devidamente calibrado para medir as tensões, em função do tempo, numa colhedora de forragem. Foram desenvolvidos modelos matemáticos para obter a variação periódica dessas tensões, considerando-se a influência da roda de apoio e da velocidade angular do rotor de corte. O ajuste dos modelos foi verificado pelo coeficiente de determinação (R²). A variação periódica das tensões, em função do tempo, para os valores experimentais e teóricos, foi representada graficamente, utilizando-se da planilha eletrônica EXCEL. Observou-se que as menores amplitudes de tensões e os maiores períodos do ciclo corresponderam aos tratamentos que utilizaram a roda de apoio. A análise estatística mostrou que a velocidade angular do rotor de corte apresentou diferença significativa, conforme o Teste de Tukey, para 5%. Com base nos resultados obtidos, concluiu-se que os ciclos de tensões em colhedoras de forragens podem ser representados com bom ajuste por funções senoidais e que o uso da roda de apoio pode aumentar o tempo de serviço da colhedora.

The study of stress in forage harvester is necessary, because the operation conditions are very different and rigorous. A calibrated datalogger system was used to measure the stress as function of time for a forage harvester. Mathematical models were developed to obtain the periodical variation of this stress by considering the influence of support wheel and the angular velocity of cutterheads. The agreement of these models was verified by the determination coefficient (R²). The periodical variation of stress as function of time for both experimental and theoretical values was graphically represented by using of the software EXCEL. It was observed that the minimal amplitude stress and the maximal periods of cycle corresponded to the treatments employed, which utilized the support wheel. The statistical analysis showed that the angular velocity of cutterheads presented significant difference, according to the Tukey Test for 5%. Based on the obtained results was concluded that, the stress cycle can be represented by senoidal functions with an adequate agreement, and that the operation time of harvesters can be increased by using a support wheel.

RESUMO O escarificador é um importante implemento de preparo primário de solo, embora nem sempre utilizado nos cerrados de forma correta, em função do pouco conhecimento que se tem a respeito de seu comportamento. Assim, instalou-se, na Escola Agrotécnica Federal de Cuiabá, um experimento com o objetivo de se avaliar o desempenho de um escarificador de hastes parabólicas no preparo primário de um solo de cerrado e obter equações que possam prever a força de tração e a potência exigidas; a área constituía-se de um Latossolo Vermelho-Amarelo, com 14,3% de argila, de cobertura vegetal média de 9.975 kgha-1 de matéria seca e de um teor médio de umidade de 13%. Os resultados obtidos mostram que os parâmetros força de tração, área mobilizada e resistência específica, não sofreram influência com a variação da velocidade, a potência aumentou e a energia consumida (kWh ha-1) diminuiu com o aumento da velocidade. A força de tração, a potência na barra e a resistência específica do solo apresentaram comportamento quadrático, em função da profundidade de preparo. A área de seção transversal de solo mobilizado apresentou comportamento linear com a variação da profundidade de operação do escarificador. A melhor eficiência, de 85,69%, foi obtida para a relação largura/profundidade de operação igual a 1,23, e a equação de McKeys, com o fator de correção de 1,08, foi eficiente para predizer a área mobilizada efetiva.

ABSTRACT The chisel plow is an important implement for tillage, but it is not always used correctly in the "Cerrados", due to limited availability of knowledge on the behavior of the chisel plow in these soils. An experiment was set up at the "Escola Agrotécnica Federal de Cuiabá" with the objective of evaluating the action of a chisel plow, with a parabolic stem, in "Cerrado" soil. The plots were set on a "Latossolo Vermelho-Amarelo", with 14.3% clay, under a mulch blanketing of 9.975 kg ha-1 (DM) and 13% soil moisture. The results show that the mobilized area and the specific resistance were not influenced by speed variation. The power increased and the energy consumption (kWh ha-1) decreased with the increase of the speed. The pull traction, power and the soil specific resistance varied quadratically with tillage depth, while the cross section at area of mobilized soil presented a linear behavior. The best efficiency of 85.69%, was obtained for the relation width/depth = 1.23. The equation of McKeys, with a correction factor of 1.08, was efficient for the prediction of the effectively mobilized area.