The use of powdered graphite as a solid lubricant to reduce friction among soybean seeds during mechanical sowing aims to facilitate the seed flow into the seed reservoir, while reducing mechanical damage to the seed. The objective of this study was to evaluate the influence of graphite on the longitudinal deposition of soybean seeds using mechanical and pneumatic feeders at different distribution velocities. The experiment was performed on a static simulation-test bench, with a completely randomized design with two varying factors: graphite dose (0, 1, 2, 4, and 8 g kg-1 seed) and distribution velocity (5, 7, 9, and 11 km h-1 for the pneumatic feeder; and 3, 5, 7, and 9 km h-1 for the mechanical feeder). To assess the homogeneity of seed distribution, the frequency of parameters such as double, flawed, and acceptable spacings, coefficient of variation, and precision index were evaluated from five repetitions of 250 spacing each. For the pneumatic feeder, the optimal values to maximize precision of seed deposition were 4.6 g kg-1 and 6.7 km h-1 of graphite dose and distribution velocity, respectively. In turn, the optimal values to minimize undesirable spacing while maximizing accuracy with the mechanical feeder were 4.9±0.6 g kg-1 and 4.9±0.3 km h-1. Overall, regardless of feeding mechanism, the use of graphite promoted greater efficiency in the distribution of seeds owing to the higher level of fluidity inside the reservoir; however, high doses can cause the opposite effect. In addition, an excessive increase in speed influenced seed distribution negatively.
Aim of study: This experiment's objective is to develop an automatic data acquisition system for profilometry, evaluating four harrowing speeds.
Area of study: Federal University of Parana, Curitiba, Brazil.
Material and methods: We experimented at the laboratory using a completely randomized design, comparing the data of modified roughness, raised and mobilized area, blistering, and thickness. These were acquired with traditional and electronic profilometers in seven replications. We executed the field test in lines, using a completely randomized design. The profilometers were in the plots and the targeted speeds in the subplots. We submitted the data for analysis of variance and when significant, to Tukey's test and regression analysis.
Main results: Laboratory testing showed no significant difference in the parameters of modified roughness, elevated and mobilized area, blistering, and thickness, denoting the phase validation that indicates applicability in the field. The field testing presented superior results for the electronic profilometer in elevated and mobilized areas and soil layer thickness. That is due to the absence of interference in the measurements that occur in the conventional profilometer caused by the insertion of the rods in the soil.
Research highlights: The increase in the mechanized set speed provided the reduction of the elevated area and soil blistering caused by the rise in disc rotation and consequent deviation of the soil particles.
The main goal of this paper is to present the design of a surface electromyography acquisition, processing and amplification system with low power consumption. Based on a micro-controller and a Bluetooth module, it must send the data to a cell phone in real time. The main topology is
based on an operational amplifier and passive components in order to produce filters and an instrumentation amplifier applied to Electromyography (EMG). This paper also shows the equations used during design and describes each step of development, from simulations and testing to acquired data
and microcontroller programming. In order to produce a low-cost circuit that can be later used as an acquisition tool for portable mechanisms and prosthesis, the design of the main circuit considers the lowest number of components while it does not compromise efficiency.
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