A particle-in-cell simulation has been adapted to analyze the helium discharge characteristics of a planar micro-dielectric barrier discharge with a gap distance less than 100 µm for variation of driving frequency from 10 to 500 MHz. Two scaling laws for the breakdown voltage were obtained with the change in heating mechanism from the γ -to the α-mode with increasing frequency. The optimal condition for the efficient generation of high-density plasmas with minimized power is obtained when the ratio of ion transit time to the RF period is about 1/4, so that the secondary electrons emitted by ion bombardment on the dielectric-gap boundary are accelerated in phase with the sheath potential. Under this condition, the plasma density as well as the ion current is maximum, the displacement current and the electron current are almost the same, and the ratio of the power delivered to the plasma is 50% of the total power. At high frequencies, the collisional electron heating increases by the induced bulk electric field, enhancing excitation and elastic collisions, and thus ionization efficiency decreases while excitation efficiency increases.
Objective. Several attempts have been made to reduce the harmful side effects and increase the efficacy of current drugs used to treat attention-deficit/hyperactivity disorder (ADHD). Many articles have studied medicinal herbs as an effective supplement in treating ADHD. In a similar manner, this study provides foundational data to identify herbs that are potentially effective in treating ADHD by text mining of Donguibogam, which is a comprehensive summation of the important traditional principles and practices of Korean medicine.Methods. Text mining was performed for 3833 herbal prescriptions and 1108 medicinal herbs comprising prescriptions listed in Donguibogam. The first step was frequency analysis followed by chi-square test, which is a statistical hypothesis test.Results and Conclusions. Twelve medicinal herbs were selected for each ADHD subtype: hyperactivity ADHD type (ADHD-PHI) and attention-deficit ADHD type (ADHD-PI). Compared to previous research on traditional literature, a newer and more efficient methodology of selecting herbal medicines was developed in this process.
The discharge characteristics of the radio frequency (RF) surface dielectric barrier discharge have been simulated for the investigation of the ratio of the ion transit time to the RF period. From one-dimensional particle-incell (PIC) simulation for a planar dielectric barrier discharge (DBD), it was observed that the high-frequency driving voltage confines the ions in the plasma because of a shorter RF period than the ion transit time. For two-dimensional surface dielectric barrier discharges, a fluid simulation is performed to investigate the characteristics of RF discharges from 1 MHz to 40 MHz. The ratio of the peak density to the average density decreases with the increasing frequency, and the spatiotemporal discharge patterns change abruptly with the change in the ratio of ion transit time to the RF period.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.