Search Results (2)

In this paper, a device with swinging plate electrodes has been proposed to measure contact electrification of a liquid sample. The proposed structure is composed of two parallel metallic plates immersed in a dielectric liquid. One of the plates is swinging with a constant frequency in a range from 0.4 to 4 Hz. The paper investigates the dependence in time and frequency of electrode velocity and streaming electrification. The measured current occurs for a very low intermittent velocity of less than 10 mm/s. In this range, the electrification current is around 50 pA. For higher velocities of up to 150 mm/s, the current is at the level of 1200 pA. The time–frequency characteristic using short-time Fourier transform shows no temporal changes in the frequency spectrum. The dependence of electrification on shuttle speed was calculated and it can be approximated with a second order polynomial model with the determination coefficient higher than 0.9. The advantage of the sensor is the ability to measure electrification phenomena without the necessity of having rotating electrodes or having a large volume of flowing liquids. Full article

The protection of potatoes from pests and diseases, especially at an early stage of their development, is an indispensable element of cultivation. Pesticides are most commonly used for protection, but their high doses may adversely affect the natural environment, including soil and water. This study compares the losses of a chemical agent emitted during the dressing of seed potatoes by means of an innovative valve enabling intermittent outflow of the liquid and by means of a standard valve with a continuous outflow. The research proved that the intermittent outflow of the working liquid decreased the amount of the chemical agent emitted into the environment ten times. The article also describes the site at which the innovative valve was tested and compares the results of laboratory tests for three distances of the sprayer from the potato fall path (50, 100, 150 mm) and four different pressures of the working liquid (1–4 kPa). The research showed that the amount of losses, i.e., emissions of the chemical agent into the environment from the innovative valve (intermittent stream of the working liquid) depended on the difference in the air and liquid pressure. The solution is environmentally friendly. The results showed that the distance between the sprayer valve and the seed potato falling path had minimal influence on the amount of the agent left on the surface of seed potatoes when a continuous stream was applied, but it had considerable influence when an intermittent stream was applied. The distance had negative effect on the ratio of retention of the applied liquid at pressures of 100 and 200 kPa, but it had positive effect at pressures of 300 and 400 kPa (at an intermittent flow). When a continuous stream was applied and the distance between the spray valve and the seed potato falling path increased from 100 to 150 mm, it had positive effect on the retention coefficient for all the four pressures tested (100, 200, 300, 400 kPa). Full article