The frequency characteristics of dielectric harrier discharge (DBD) have been studied for optimizing discharge efficiency. The experiment was performed with various experiment conditions to find the relation between the discharge frequency and power consumption. There is the optimum discharge frequency, which minimizes the consumption of the electrical power. Physically, the optimum discharge frequency means the inverse of the charge build-up time on the dielectric materials. Hence, the optimum discharge frequency depends on the capacitance of a reactor, which is a function of the geometry of the reactor and dielectric materials, and discharge conditions, which depends on the discharge voltage, and gases. From the experimental results, a semi empirical relation on the optimum frequency can he expressed as a function of the discharge gap, dielectric materials, sort of electrodes, and discharge gases.The use of atmospheric pressure air plasmas as reflectors for microwave radiation with frequencies up to 30 GHz requires electron densities of approximately IO" cm". It has been shown, that direct cument microhollow cathode sustained (MCS) discharges meet this requirement [I]. However, the power consumption of such air glow discharges of 5 kW/cm3 does not permit scaling to large volumes. Pulsing the discharge on a time scale, which is less than the characteristic time for glow-to-arc transition allows us to reduce the power density while keeping the average electron density at the required high value 121. So far the electron density in these pulsed discharges has been estimated using information on the plasma conducCvity; data on the electron energy which is sharply shifted towards higher energies during the pulse have only been obtained through modeling. We have measured the eleclron density in a pulsed atmospheric air plasma by means of heterodyne interferometry 131. A measure for the electron energy. the electron temperature, was obtained by means of emission spectroscopy. 20% argon was added to atmospheric air, and the relative intensities of two argon lines, at 810.37 nm and 811.52 nm, were measured. Assuming a Maxwell-Boltamann distribution of the electron energies allowed us to determine a value for the electron temperature. For a 10 ns pulse of 1.6 kV superimposed to a direct current discharge between electrodes 1.6 mm a art, the electron density increased from IO" cm" to more than 3 IO cm I. Over a time of 600 ns it decayed by one order of magnitude. Higher values of the electron density, and correspondingly longer decay times, which are determined by recombination, can be achieved by increasing the pulsed electric field 121. The electron temperature reached values of 50 eV. This value is in accordance with modeling results. The presence of such high energy in relatively large plasma volumes indicates that pulsed high pressure discharges in air, but also in other gases, have applications not only a plasma ramparts but also a plasma reactors, e.g for chemical decontamination. Other applications, where both high...
Unreinforced masonry buildings have significant portion of existing and historical buildings around the world. Recent earthquakes have shown the needs of seismic retrofitting for these types of buildings. There are many types of retrofitting materials for URM(unreinforced masonry buildings) such as shotcrete, ECC and FRPs. Many engineers use many types of fiber reinforced polymers because these types of material enhance the shear strength of wall without expansion of wall sectional area and additional weight of total structure. However, the complexity of mechanical behavior of masonry shear wall and the lack of experimental data of masonry wall which was retrofitted by FRPs may cause the problem that engineers hard to determine the retrofitting level. Determining and providing the information for retrofitting effect of FRPs for masonry shear wall, this paper investigate in-plane shear behavior of URM and retrofitted masonry shear walls using two types of different FRP materials. Specimens were designed to idealize the wall of low rise apartment which was built in 1970s Korea with no seismic reinforcements and have 1 aspect ratio. Retrofitting materials were carbon FRP and Hybrid sheet which have different elastic modulus and ultimate strain. Consequently, this study will evaluate the structural capacity of masonry shear wall and retrofitting effect of FRP sheet for in plane shear behavior comparing with evaluation method for reinforced concrete beam which was retrofitted by FRPs.
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