Engenharia Agrícola - Artigos
URI permanente para esta coleçãohttps://locus.ufv.br/handle/123456789/11739
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Item Automatic regulator for channel flow control on flooded rice(Agricultural Water Management, 2005-07-25) Amaral, Luís G. H. do; Righes, Afrânio Almir; Souza Filho, Paulo da S. e; Costa, Rafael DallaThe low efficiency water control provided by sluice gates and weirs used in the flooded rice tillage system in Rio Grande do Sul, Brazil, have caused significant water losses. Such devices are utilized to control the water flow from the main to the secondary channels. The water flow through the gates is highly influenced by the water depth fluctuation in the main channel. The purpose of this work was to construct and evaluate a flow regulator to reduce flow variations in the secondary channels, resulting from water level fluctuation in the main channels. The prototype operates with a float that prevents the water head variation over the water passage orifices. The regulator flow control was compared to the sluice gate flow control. Both structures were installed at a lateral inlet, and the depth of water in the main channel ranged from 70 to 90 cm. The flows from the regulator and sluice gate were measured with “H” flumes. To relate the flow provided by the regulator to the water head over the water passage orifices, the regulator was submitted to six different water heads, ranging from 5 to 30 cm. The comparison between the structures showed that both presented variation in the controlled flow. However, the flow control provided by the automatic flow regulator was more effective than that provided by the sluice gate. The controlled flow variation was 5.5% for the automatic flow regulator, and 23.7% for the sluice gate. Regulator flow analysis for the different water heads showed that it can operate with flows ranging from 24 to 49 L s−1. Comparing the sluice gate to the automatic flow regulator, the latter is a more efficient flow control device, reducing the waste of water.Item Bioactivity of Jatropha curcas L. to insect pests of stored products(Journal of Stored Products Research, 2011-11-15) Silva, G. N.; Faroni, L. R. A.; Sousa, A. H.; Freitas, R. S.The objective of this research was to assess insecticidal activity of seeds and derivatives of Jatropha curcas to insect pests of stored grains. Lethal exposure times were estimated for 50 and 95% (LT50 and LT95) of the adults of Sitophilus zeamais and Rhyzorpertha dominica to seeds of four genotypes of J. curcas: Gonçalo, Paraguaçu, Filomena and Bento. Toxicity of powders and aqueous extracts from seeds and pericarps of J. curcas were tested on S. zeamais, R. dominica, Tribolium castaneum and Oryzaephilus surimanensis. A uniform toxic response was observed among the four genotypes for S. zeamais and R. dominica. The powders and aqueous extracts from seeds and pericarps were lethal to S. zeamais, R. dominica, T. castaneum and O. surimanensis. However, insect mortality was higher in the treatments from seeds, compared to the treatments from pericarps.Item CFD modelling of diffusive-reactive transport of ozone gas in rice grains(Biosystems Engineering, 2019-03) Silva, Marcus Vinicius de Assis; Martins, Márcio Aredes; Faroni, Leda Rita D'Antonino; Vanegas, Jaime Daniel Bustos; Sousa, Adalberto Hipólito deThe search for alternatives to the use of chemical products to control insect pests in stored grains has stimulated the development of new techniques that allow the maintenance and preservation of grain quality without posing risks to people and the environment. One of these alternatives is the use of ozone gas (O3) as a fumigant, mainly due to its oxidising and biocidal characteristics. To investigate the transport mechanisms involved in the flow of the O3 gas through rice grains, the CFD (Computational Fluid Dynamics) analysis was used, and from this evaluation, it was possible to predict the decomposition reaction constant and the O3 effective diffusion coefficient. In the experiment, grains were submitted to fumigation process in a prototype adapted from a diaphragm cell. Data on the ozone gas concentration were collected from a monitoring point immediately above the grain layer every 10 min. Parallel to the experimental procedure, the modelling of the O3 gas flow using the CFD technique was performed. The adjustment parameters input to the CFD model were the effective diffusion and the decomposition reaction constant of the O3 gas in the rice grains. The estimated diffusivity value (1.0 × 10−6 m2 s−1), and decomposition reaction constant (0.00167 s−1) are of the same order of magnitude of several other gases for agricultural grains.Item Difenoconazole and linuron dissipation kinetics in carrots under open-field conditions(Ecotoxicology and Environmental Safety, 2019-01-30) Souza, Lauana Pellanda; Faroni, Lêda Rita D’Antonino; Heleno, Fernanda Fernandes; Pinto, Frederico Garcia; Queiroz, Maria Eliana Lopes Ribeiro; Prates, Lucas Henrique FigueiredoThe dissipation of difenoconazole and linuron using an open-field experimental approach with carrots exposed to one-, two- and fivefold the recommended dose of the pesticides was evaluated to provide safe recommendation to ensure food safety of carrots. The pesticide residue analysis was performed with solid-liquid extraction with low temperature partitioning technique (SLE/LTP) followed by gas chromatography analysis. The recovery percentages of extracts obtained from samples of carrot passed through SLE/LTP extraction and fortified with difenoconazole and linuron pesticides varied from 93.4% to 106.3% and from 95.1% to 116.6%, respectively. The limit of detection for difenoconazole was 0.02 and 0.12 mg kg−1 for linuron. The limit of quantification for difenoconazole was 0.05 and 0.36 mg kg−1 for linuron. The degradation time for fifty percent of the applied pesticide at the different doses ranged from 2.4 to 3.6 days for difenoconazole and from 7.5 to 10.5 days for linuron. At the end of the pre-harvest interval, carrots treated with fivefold the recommended dose of both pesticides were considered unfit for consumption. Despite monitoring the degradation products of the applied pesticides by gas chromatography coupled to mass spectrometer, none degradation product was identified on the carrots.Item Experimental characterization of self-heating behavior of charcoal from eucalyptus wood(Fuel, 2019-05-15) Bustos-Vanegas, Jaime Daniel; Martins, Marcio Arêdes; Freitas, Arthur Gomes; Mellmann, JochenThe long cooling time of charcoal produced from eucalyptus pyrolysis is due in part to the heat generation in oxidation reactions at low temperatures. The intensity of this reactions depends on complex interactions between the interstitial gas and the solid matrix. The objective of this paper was to investigate the kinetics of the self-heating phenomena due to charcoal oxidation at low temperatures and at different oxygen concentrations. Samples of 230 g of charcoal were subjected to heating in a steel reactor at constant temperature, from 100 to 300 °C, and oxygen concentrations ranging from 20.9 to 10%. Was evidenced that the rate of oxygen consumption increases with charcoal temperature at rates that depend on the initial concentration of O2. The beginning of the oxidation reactions was observed at 67 °C in atmospheres with 20.9% O2. The overall activation energy for the self-heating phenomenon was 17,790 J mol−1 and its intensity was increased with the temperature and O2 concentration.Item The influence of plant roots on the clogging process and the extractive capacity of nutrients/pollutants in horizontal subsurface flow constructed wetlands(Ecological Engineering, 2018-09) Teixeira, Denis Leocádio; Matos, Antonio Teixeira de; Matos, Mateus Pimentel de; Vieira, Delilah Pires; Araújo, Edcássio Dias; Ferraz, Liliane AparecidaThe root system of plants grown in horizontal subsurface flow constructed wetlands (HSSF CWs), although it favors the removal of nutrients/pollutants from the wastewater under treatment, can contribute to the clogging of these systems. The objective of this work was therefore to evaluate the influence of Vetiver and Tifton 85 grass roots on the process of clogging and extraction of nutrients/pollutants in HSSF CWs. The drainable porosity in the medium was quantified before planting and after 250 days of cultivating the above-mentioned grass, having obtained the volume, productivity and nutrient extraction of the roots and shoots of these plants. There was a reduction in the porosity of the medium in the HSSF CWs due to the development of roots of the Vetiver and Tifton 85 grasses in the medium, however these roots occupied only 3.07 and 4.11% of the total pore space, respectively, and therefore are not factors of great influence in clogging process. HSSF CWs cultivated with Vetiver grass presented higher extractions of K and P by the roots, especially when the medium saturating solution presented greater availability of nutrients. On the other hand, higher extraction capacity of nutrients/pollutants was presented by the Tifton 85 shoots.Item Review of the photovoltaic energy program in the state of Minas Gerais, Brazil(Renewable and Sustainable Energy Reviews, 2011-05-05) Cabral, Claudia Valéria Távora; Oliveira Filho, Delly; Diniz, Antonia Sonia Cardoso; Machado Neto, Lauro V.B.; Camara, Carlos F.; Morais, Paulo M R; Ravinetti, Regina F.; França, Edson D.; Cassini, Denio A.; Souza, Márcio E. M.; Santos, José H.; Amorim, MaraIn much of the world, there is increasing demand for electricity to serve rural communities, isolated from the existing grids and typified by low-density electrical consumption. Because these non-urban consumer markets require rather high implementation investments (as well as high operation and maintenance costs), new technological and policy options are required to meet the needs of these markets. These consumers typically use energy in daytime peak hours of electricity, typically for lighting, television, and communication—as well as for a variety of cultural habits such as hot water that impose high demands on the utility's power distribution and generation system. This has been the case in Brazil, making it necessary to identify decentralized generation technologies to meet the potential markets, typically serving rural and poorer areas. The government itself provided the impetus with the passage of the Brazilian “Universalization Law” that mandated supplying electricity access for the entire population by the year 2010. This law allows the use of both the distribution grid and renewable energy off-grid technologies. In response, Brazil's largest state utility, Energetic Company of Minas Gerais (CEMIG) has aggressively implemented the use of decentralized photovoltaic systems to supplement the conventional power grid to satisfy the “universalization” targets. This paper provides a summary of the status and the future prospects of solar photovoltaic Energy in Brasil, within the context of the “universal electricity supply” policy. The focus here is to highlight the successes and the issues experienced to date in the State of Minas Gerais. This includes examining the methods implemented to ensure system reliability for the consumers, as well as the standards established under the Agéncia Nacional de Energy Elétrica (ANEEL), the national regulator electrical agency that ensures compliance with the federal regulations.