An Experimental Study on Atmospheric Pressure Glow Discharge in Different Gases

Usually, the electrical breakdown of dielectric barrier discharge (DBD) at atmo-spheric pressure leads to a filamentary non-homogeneous discharge. However, it is also possible to obtain a diffuse DBD in homogeneous form, called atmospheric pressure glow discharge (APGD). We obtained a uniform APGD in helium and in the mixture of argon with alcohol, and studied the electrical characteristics of helium APGD. It is found that the relationship between discharge current and source frequency is different depending on the difference in gas gap when the applied voltage is kept constant. The discharge current shows an increasing trend with the increased frequency when gas gap is 0.8 cm, but the discharge current tends to decrease with the increased frequency when the gas gap increases. The discharge current always increases with the increased applied voltage when the source frequency is kept constant. We also observed a glow-like discharge in nitrogen at atmospheric pressure.

Experimental Study on RF Hollow Cathode Discharge

By using a longitudinal static magnetic field, we have shown that it is possible to excite an intensive plasma in a simple stainless steel tube which is connected with a RF power supply. Under certain conditions, the very bright Ar II lines were excited. The emission intensities of Ar II lines were increased with the increase in RF power, magnetic field, and the decrease in argon pressure. As the plasma-sheath boundary oscillating under the RF voltage, the plasma column is periodically compressed by the oscillating boundary.

Experimental study of mean overtopping discharge at perforated caissons for non-impulsive waves

In this study, hydraulic model tests are carried out to investigate the mean overtopping discharge at perforated caisson breakwaters for non-impulsive waves. Based on the experimental data, the mean overtopping discharges of perforated and nonperforated caissons are compared. It is found that when the relative crest freeboard is smaller than 1.6, the mean overtopping discharge of a breakwater can be reduced by at least half by using perforated caissons with 35% porosity instead of nonperforated caissons. The effects of the relative crest freeboard, the caisson porosity and perforation shape, the relative wave chamber width and the relative water depth on the mean overtopping discharge at perforated caissons are clarified. Then,predictive formulas for the mean overtopping discharge at perforated caissons are developed. The predictive formulas based on the experimental data are valid in a wide range of the relative crest freeboard and involve the effects of the caisson porosity and the relative water depth. The predictive formulas developed in this study are of significance for the hydraulic design of perforated caissons.

Testifying experiment of the multi-pulse phenomena of capillary discharge soft-X-ray laser

In a capillary discharge experiment for the neon-like argon lasing, we have proposed an experimental scheme to verify that the multi-spike of X-ray diode （XRD） signal is a multi-pulse laser or is a reflection of the laser pulse in the XRD. The ceramic capillary has an inner diameter of 3 mm and a length of 200 mm. At the gas pressure of 28 Pa and discharge current of 27 kA, stable lasing has been realized. The experimental results prove that the multi-spike of XRD signal is a reflection of the electromagnetic signal produced by the laser pulse in the XRD. The improved electrocircuit scheme of the XRD to minimize the reflection phenomena is also found.

Assessment of agri-spillways as a soil erosion protection measure in Mediterranean sloping vineyards

Suitable vineyard soils enhance soil stability and biodiversity which in turn protects roots against erosion and nutrient losses. There is a lack of information related to inexpensive and suitable methods and tools to protect the soil in Mediterranean sloping vineyards(>25° of slope inclination). In the vineyards of the Montes de Málaga(southern Spain), a sustainable land management practice that controls soil erosion is actually achieved by tilling rills in the down-slope direction to canalize water and sediments. Because of their design and use, we call them agri-spillways. In this research, we assessed two agri-spillways(between 10 m and 15 m length, and slopes between 25.8° and 35°) by performing runoff experiments under extreme conditions(a motor driven pump that discharged water flows up to 1.33 l s^(-1) for 12 to 15 minutes: ≈1000 l). The final results showed: i) a great capacity by these rills to canalize large amounts of water and sediments; and, ii) higher water flow speeds(between 0.16 m s-1 and 0.28 m s^(-1)) and sediment concentrationrates(up to 1538.6 g l^(-1)) than typically found in other Mediterranean areas and land uses(such as badlands, rangelands or extensive crops of olives and almonds). The speed of water flow and the sediment concentration were much higher in the shorter and steeper rill. We concluded that agri-spillways, given correct planning and maintenance, can be a potential solution as an inexpensive method to protect the soil in sloping Mediterranean vineyards.