Abstract Low density sugarcane plantation (LDSP) has been implemented by some sugarcane producers in Brazil, aiming to save seeds and operational costs. The study was carried out in the municipality of Areia, Paraíba, Brazil. Five planting densities were used, varying from 5 to 25 m-2 of buds arranged in randomized blocks, with four replications. Data were measured annually over three cultivation cycles (2017 to 2020), during which the field was fertilized with NPK and the harvests were carried out manually without prior burning. The lower planting density presents higher productivity only in the cane plant (101.03 t ha-1) due to the higher plant height (2.37 m) and the higher number of stalks (11 stalks m-2), suggesting that these variables are due to the greater availability of light, water and photosynthate. However, there is a drastic reduction in sugarcane yield for this lower population in the 2nd ratoon by up to 65.62%, which is correlated with number of stalks per meter. We demonstrate the agronomic viability of LDSP in the population of 10 buds m-2 in relation to conventional planting of sugarcane until the 2nd ratoon. Data are important for future studies to present additional considerations for other production factors, such as the effects of mechanized harvesting and the management of nutrients and water, assessing the sustainability of this large-scale planting system.

Resumo O método de plantio de cana-de-açúcar de baixa densidade (LDSP) vem sendo implementado por alguns produtores de cana-de-açúcar no Brasil, visando economia de sementes e custos operacionais. O estudo foi realizado no município de Areia, Paraíba, Brasil. Utilizou-se cinco densidades de plantio, variando de 5 a 25 m-2 de gemas dispostas em blocos casualizados, com quatro repetições. Os dados foram medidos anualmente ao longo de três ciclos de cultivo (2017 a 2020). Menor densidade de plantio mostrou maior produtividade (101,03 t ha-1) devido à maior altura de planta (2,37 m) e ao maior número de hastes (NS) (11 hastes m-2), sugerindo que essas variáveis são devido à maior disponibilidade de luz, água e fotoassimilados. No entanto, houve redução drástica na produtividade da cana-de-açúcar para esta população menor na 2ª soca em 65,62%, estando correlacionado com o número de colmos por metro. Demonstramos a viabilidade agronômica do LDSP em uma população de 10 gemas m-2 em relação ao plantio convencional de cana-de-açúcar até a 2ª soca. Os dados são importantes para que estudos futuros apresentem considerações adicionais sobre outros fatores de produção, como os efeitos da colheita mecanizada e do manejo de nutrientes e água, avaliando a sustentabilidade desse sistema de plantio em larga escala.

This study analyzes the heat transfer in human eyes following implantation of retinal prostheses using an axisymmetric formulation of the Finite Volume Method. The model used consisted of a vertex centered unstructured grid finite volume method in an edge-based data structure and an explicit time integration. The results of the finite volume thermal analysis in ocular tissues were determined in the presence of two types of retinal implants: subretinal and epiretinal. For the subretinal device, the maximum temperature reached in the retina was 36.78°C (309.78 K) and the irreversible thermal damage occurred at 200 days. In the case of the epiretinal implant, the maximum temperature reached at the retinal/chip interface was 36.92°C (309.92 K) and the irreversible thermal damage occurred at 180 days. Our results indicate that tin spite of its higher dissipation power, the epiretinal implant produces thermal damages similar to that caused by the subretinal implant. The computational tool which was developed was able to effectively calculate temperature profiles and thermal damage values to retinal implants and is also capable to calculate temperature profile in any other geometry of interest, for example with other types s of external thermal source like laser beans.

In this work, a finite volume formulation developed for two-dimensional models is extended to deal with axisymmetric models of heat conduction applications. This formulation uses a vertex centered finite volume method and it was implemented using an edge-based data structure. The time and domain discretization using triangular meshes is described in details, including the treatment of boundary conditions, source terms, and domains with multiple materials. The proposed formulation is validated and proves to be effective and flexible through the solution of simple model problems.