Nithiphat Teerakawanich

Rice (Oryza sativa L.) Seed Sterilization and Germination Enhancement via Atmospheric Hybrid Nonthermal Discharge Plasma

We designed a system to produce atmospheric hybrid cold-discharge plasma (HCP) based on microcorona discharge on a single dielectric barrier and applied it to inactivate microorganisms that commonly attach the rice seed husk. The cold-plasma treatment modified the surface of the rice seeds, resulting in accelerated germination and enhanced water imbibition. The treatment can operate under air-based ambient conditions without the need for a vacuum. The cold-plasma treatment completely inactivated pathogenic fungi and other microorganisms, enhancing the germination percentage and seedling quality. The final germination percentage of the treated rice seeds was ∼98%, whereas that of the nontreated seeds was ∼90%. Microcorona discharge on a single dielectric barrier provides a nonaggressive cold plasma that can be applied to organic materials without causing thermal and electrical damage. The hybrid nonthermal plasma is cost effective and consumes relatively little power, making it suitable for the surface sterilization and disinfection of organic and biological materials with large-scale compatibility.

Microcorona Discharge-Mediated Nonthermal Atmospheric Plasma for Seed Surface Modification

By exploiting the physical effect of a highly nonuniform localized electric field and electron-initiated impact ionization on space charge, we generated homogeneous nonthermal plasma under ambient atmosphere. We evaluated the physical characteristics and evolution of microcorona discharge-induced nonthermal atmospheric plasma (NAP) based on a point-to-plane electrode in open air with two distinct configurations. High-voltage pulses were employed as the primary power source of corona discharge generation to reveal the fundamental mechanism, polarity effect and feasibility of using NAP for organic surface modification. Consequently, we employed NAP to modify the surface of rice (Oryza sativa L.) seeds to improve their wettability. The surface modification of the rice seeds was investigated via water apparent contact angle (ACA) and water imbibition (WI) measurements. The ACA and WI measurements revealed not only the improvement in the wetting properties but also the mutual relationships between and limitations of ACA and WI analysis. We found that the WI time reached saturation after a certain treatment time, called the threshold treatment time. Because vacuum conditions are not required, well-established NAP technology will garner interest in many fields, ranging from the life, environmental, and biomedical sciences to solid-state electronics applications.

Coordinate operation of fuzzy logic voltage regulator and Bi-2212 SFCL for enhancing fault ride through capability of DFIG wind turbines

With penetration of wind turbines, fault ride through capability is unconditionally considered as one of the most remarkable research area. Hence, this paper proposes the fault ride through capability improvement of DFIG wind turbines by using cooperative operation of fuzzy logic voltage regulator and Superconducting Fault Current Limiter (SFCL). BSCCO (Bi-2212) superconducting coil material is fully introduced to investigate in this paper. Under large disturbances such as faults, fuzzy logic voltage regulator is directly utilized to enhance a voltage dip at the DFIG terminal. Nevertheless, a high peak fault current cannot be deducted. For this reason, the Bi-2212 SFCL is used for fault current reduction simultaneously. As the simulation results, the proposed fuzzy logic voltage regulator and Bi-2212 SFCL combinative operation have a superior performance to diminish a peak current and improve fault ride through capability for Swedish grid code requirement.

Polarity effect of pulsed corona discharge plasma on seed surface modification

This paper presents an experimental analysis and underlying mechanism of positive and negative pulsed corona discharge induced atmospheric non-thermal plasma. We designed a system based on point-plane configuration to produce direct corona discharge plasma (DCP) and hybrid corona discharge plasma (HCP) systems. The polarity effect of corona discharge for surface modification application on rice seeds was investigated under atmospheric dry air ambient. The reactive species under negative and positive corona discharge plasma were also studied for optimization design. The results show that only negative pulsed corona discharge is feasible for DCP system while both positive and negative pulsed corona discharge can be employed for in HCP system.

Phase-shift phase-lock loop (PLL) control for wireless power transmission system using primary-side information

This paper presents a development of a low power wireless power transmission system. A phase shift phase-lock loop (PLL) control for WPT was also proposed. The proposed control strategy was used to optimize the phase offset between the fundamental primary side voltage and primary side current at all operating points. Then, the phase compensation can be achieved. In order to verify the proposed control scheme, a hardware prototype of the proposed wireless power transmission (WPT) system has been constructed. The coupling coefficient was measured at different air gaps and lateral offsets. Several simulations and experimental results such as voltage and current measurement of primary voltage and current were reported and discussed.

The study of reactive power control strategies of PV plant in PEA distribution system

Due to the significantly increasing of Photovoltaic generations in distribution system, many utilities have reported about the adversely impact of high penetration PV on voltage variations. The various reactive power control strategies have been proposed to solve this issue. The aim of this paper is to study the performance of the implementation of three reactive power control strategies i.e. cosφ, cosφ(P) and Q(U) in Provincial Electricity Authority (PEA) distribution system. The large-scale PV Plant in this study built by DIgSILENT PowerFactory is used to perform simulation. The simulations are shown the voltage improvement and feeder losses on the different reactive power control strategies, by comparing with the base case (PV is generating the maximum active power and not injecting reactive power). The results are expected to use as a guideline for further development of PEA grid code.

Vacuum electron-based photodiode

We have presented a detailed investigation of hybrid photodiode based on the combination of Gr/Si heterojunction and nanoscale vacuum device based on graphene-SiO2-Si (GrOS) field effect structure. We elucidate on the underlying mechanism of impact-ionization process in a two-Dimensional Electron Gas (2DEG) confined in quantum well, resulting in increasing the carrier multiplication and enabling ultrahigh speed optoelectronics.