Koichi Takaki

By Koichi Takaki, Katsuyuki Takahashi and Yuichi Sakamoto

High-voltage electrical stimulation is effective for promotion of fruit-body development in mushroom cultivation. The high voltage applying to cultivation bed of mushroom generates intense electric field inside the bed substrate. The intense electric field accelerates the hypha move owing to the electrostatic force. As a result, some parts of hyphae are cut and scratched. The cutting and scratching of hypha work as stimulation for promotion of the fruit-body development. The promotion effect of high-voltage stimulation to sawdust-based substrate of L. and natural logs hosting Lentinula edodes, Pholiota microspora and Hypholoma lateritium are confirmed through the experiment in the cultivation field. The fruit-body formation of mushrooms increases 1.3–2.0 times in terms of the total weight. The accumulated yield of L. edodes for four cultivation seasons is improved from 160 to 320 g by applying high voltage of 50 or 100 kV. However, the yield decreases from 320 to 240 g upon increasing applied voltage from 100 to 130 kV. The yield of the other types of mushrooms shows tendencies similar to those of L. edodes by applying high voltage. An optimal voltage exists for efficient fruiting body induction.

Part of the book: Physical Methods for Stimulation of Plant and Mushroom Development

By Katsuyuki Takahashi, Koichi Takaki, Isao Hiyoshi, Yosuke Enomoto, Shinichi Yamaguchi and Hidemi Nagata

The corona discharge ionizer has been widely used to eliminate electrostatic charges on insulators in a variety of manufacturing industries for the prevention of electrostatic discharge (ESD) problems. High-speed electrostatic elimination is conventionally required for ionizer performance. Because of the high sensitivity of recent electronic devices to ESD damage, an extremely low-offset voltage (ion balance) is required for the performance of electrostatic eliminators. Long-term performance stability is required to maintain the quality of the products, but the short cleaning interval of the unit increases the operating cost. The efficiency is also affected by the waveform of the applied voltage. The optimization of the applied voltage is an important factor in achieving long-term performance stability. In this study, an intermittent pulse voltage AC power supply was developed to achieve a highly efficient electrostatic elimination with long-term stability high-speed electrostatic elimination and an excellent ion balance.

Part of the book: Modern Applications of Electrostatics and Dielectrics

By Katsuyuki Takahashi, Koichi Takaki and Naoya Satta

Electrical pulsed discharge plasma produces various powerful oxidizing agents, such as hydroxyl radicals and ozone, which have high oxidation potential. These species play an important role in the decomposition of persistent organic compounds in wastewater. Because highly concentrated oxidants are directly produced inside the plasma, plasma realizes high-speed wastewater treatment without pretreatment of samples, such as pH adjustment. The pulsed discharge plasma generated over the water surface and inside bubbles is highlighted as a highly efficient method for plasma generation and radical supply into wastewater. In this paper, the physical and chemical properties of the discharge plasma generated over a water surface are described. The decomposition of persistent organic compounds dissolved in wastewater, such as 1,4-dioxane, formic acid, and dichloromethane, by plasma discharge is demonstrated, and their mechanisms are discussed. These persistent compounds, which have strong toxicity and stability, can be efficiently decomposed and removed quickly from solutions by plasma treatment. Furthermore, the treatment of nutrient solutions used in hydroponic systems for plant cultivation is also introduced as a novel application of plasma, and the effects of bacterial inactivation, decomposition of allelochemicals, and improvement in plant growth by plasma are demonstrated.

Part of the book: Sewage