The influence of vibration on the spatiotemporal structure of the pattern in dielectric barrier discharge is studied for the first time. The spatiotemporal structure of the pattern investigated by an intensified charge-coupled device shows that it is an interleaving of three sublattices, whose discharge sequence is small rods–halos–large spots in each half-cycle of the applied voltage. The result of the photomultiplier indicates that the small rods are composed of moving filaments. The moving mode of the moving filaments is determined to be antisymmetric stretching vibration by analyzing a series of consecutive images taken by a high-speed video camera. The antisymmetric stretching vibration affects the distribution of wall charges and leads to the halos. Furthermore, large spots are discharged only at the centers of the squares consisting of vibrating filaments. The vibration mechanism of the vibrating filaments is dependent on the electric field of wall charges.
The variation of oil film distribution in the line contact area of pin and disk was experimentally observed during a periodic intermittent motion. The study was conducted on a ball-disk optical interferometric test rig, with motion speed controlled by PLC programming. PAO40 oil was primarily used in the experiment, with the glass disk undergoing periodic motion of constant speed-deceleration-stop-acceleration, while the pin roller remained fixed. The results indicate that when the motion stops, a portion of the oil is entrapped in the center of the contact area. As the acceleration phase begins, this portion of the oil is gradually squeezed out of the contact area, and the oil film with lowest thickness at the entrance of the contact area moves towards the exit of the contact area, passing through the contact center. It can also be observed that during the entire process, an increase in speed increases the film thickness, while an increase in deceleration time, i.e., a decrease in deceleration, reduces the film thickness during the stop phase.
The enhancement of plasma generation in atmospheric pressure dielectric barrier discharge (DBD) is gaining increasing interest for various plasma applications. In this paper, the effect of surface charges moving with the rotating dielectric plate on improving the generation of streamer channels is investigated by a statistical analysis of electrical measurements, optical diagnostics, and numerical simulation in a needle-plate DBD device with a rotating dielectric plate. Results suggest that rotating the dielectric plate can improve the spatiotemporal distribution of streamer channels by inducing a bending of the streamer channels and an increase in the number of discharges. Statistical results show that the number of current pulse and discharge energy are increased by 20% and 47%, respectively, at the rotating speed of 160 rps (revolution per second). Based on the interaction between the applied electric field and the electric field induced by surface charges, a formula is proposed to govern the effect of rotating the dielectric plate on the discharge energy and streamer bending. To further understand the mechanism of the influence of rotating the dielectric plate on plasma properties, a 2D fluid model is implemented, and the reduced electric field and streamer propagation are analyzed. Results show that the effective transfer and reuse of surface charges play an important role in the enhancement of plasma generation.
The linear-zigzag transition is observed and studied in dielectric barrier discharge with rectangular frames for the first time by two photomultipliers, an intensified charge-coupled device, and a high-speed video camera. The unstable linear spot pattern transforms into a stable zigzag superlattice pattern with increasing voltage. The zigzag superlattice pattern is made up of dim spots at each corner, light spots between dim spots, and a zigzag line which is composed of moving spots and zigzag halos. All the spots in the linear spot pattern discharge simultaneously, and they have equal electric quantities, while the discharge sequence in the zigzag superlattice pattern is light spots, dim spots, halos, moving spots, and electric quantities of light spots are more than that of dim spots. The difference in the electric quantities leads to the formation of zigzag halos. In a word, the zigzag superlattice pattern results from unequal wall charge quantities of different sublattices and statistical self-organization of moving spots.
An HPLC method for the determination of 18alpha-glycyrrhetinic acid and 18beta-glycyrrhetinic acid in rat plasma was established, which was used subsequently to determine the pharmacokinetic profiles of both epimers of glycyrrhetinic acid in rats. alpha-glycyrrhetinic acid, beta-glycyrrhetinic acid, and a mixture of alpha-glycyrrhetinic and beta-glycyrrhetinic acids were administered to rats via gastric infusion. Blood samples were collected at different time intervals and extracted by liquid-liquid extraction. Separation was achieved by using a Kromasil C18 column (150 mm x 4.6 mm, 5 microm) with the mobile phase composed of acetonitrile--4 mmol x L(-1) ammonium acetate solution (46 : 54, v/v) at a flow rate of 1.0 mL x min(-1), and the detection wavelength was set at 250 nm. The pharmacokinetic parameters were calculated using the software DAS 2.0. In a combined administration, the main pharmacokinetic parameters of beta-glycyrrhetinic acid are significantly different from that of alpha-glycyrrhetinic acid (P < 0.05), while no significant difference was obtained when administrated individually. Compared to the single administration, significant differences (P < 0.05) on the values of AUC(0-t) and AUC(0-infinity) of beta-glycyrrhetinic acid were observed when this chemical was administrated together with alpha-glycyrrhetinic acid. In contrast, the pharmacokinetic parameters of alpha-glycyrrhetinic acid were not affected even under the co-administration. Here, a sensitive, specific, rapid and reproducible HPLC method was developed for the pharmacokinetic studies of alpha-glycyrrhetinic acid and beta-glycyrrhetinic acid in rat plasma.
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