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Nishijima, S. The Korea Institute of Applied Superconductivity a 2019 한국초전도저온공학회논문지 Vol.21 No.2
The superconducting magnetic separation system has been developing to separate the iron oxide scale from the feed water of the thermal power plant. The accumulation in the boiler lowers the heat exchange rate or in the worst case damages it. For this reason, in order to prevent scale generation, controlling pH and redox potential is employed. However, these methods are not sufficient and then the chemical cleaning is performed regularly. A superconducting magnetic separation system is investigated for removing iron oxide scale in a feed water system. Water supply conditions of the thermal power plant are as follows, flow rate 400 t / h, flow speed 0.2 m / s, pressure 2 MPa, temperature $160-200^{\circ}C$, amount of scale generation 50 - 120 t / 2 years. The main iron oxide scale is magnetite (ferromagnetic substance) and its particle size is several tens ${\mu}m$. As the first step we are considering to introduce the system to the chemical cleaning process of the thermal power plant instead of the thermal power plant itself. The current status of development will be reported.
S. Nishijima 한국초전도.저온공학회 2019 한국초전도저온공학회논문지 Vol.21 No.2
The superconducting magnetic separation system has been developing to separate the iron oxide scale from the feed water of the thermal power plant. The accumulation in the boiler lowers the heat exchange rate or in the worst case damages it. For this reason, in order to prevent scale generation, controlling pH and redox potential is employed. However, these methods are not sufficient and then the chemical cleaning is performed regularly. A superconducting magnetic separation system is investigated for removing iron oxide scale in a feed water system. Water supply conditions of the thermal power plant are as follows, flow rate 400 t / h, flow speed 0.2 m / s, pressure 2 MPa, temperature 160 - 200 ° C, amount of scale generation 50 - 120 t / 2 years. The main iron oxide scale is magnetite (ferromagnetic substance) and its particle size is several tens μm. As the first step we are considering to introduce the system to the chemical cleaning process of the thermal power plant instead of the thermal power plant itself. The current status of development will be reported.
Novel Low Cost Ripple Based Controlled Pulse Width Modulator for Fast Transient Response
S.Hirose,K.Ono,T.Sato,T.Nabeshima,K.Nishijima 전력전자학회 2011 ICPE(ISPE)논문집 Vol.2011 No.5
This paper presents novel pulse width modulation circuit for fast transient response. In the proposed modulator, C-MOS logic inverters are used instead of high speed comparators. Four types of new modulator are proposed and operating principle described in detail. The proposed modulator is applied to a buck converter, and steady state characteristics and frequency response of the proposed modulator are measured with the bread board circuit. From the experimental result, it is found that the proposed modulator has the derivative characteristics as hysteretic PWM controller that has good transient performance. Excellent load and line regulation are obtained. By using C-MOS inverter, compared with conventional hysteretic PWM controller with fast comparator, cost is reduced to one-fifth.
Separation of Micro-plastics from Sea Water Using Electromagnetic Archimedes Force
N. Nomura,F.Mishima,S.Nishijima 한국초전도저온학회 2023 한국초전도저온공학회논문지 Vol.25 No.3
Pollution of the environment by micro-plastics is now a worldwide problem. Plastics are difficult to decompose and put a greatload on the marine environment. Especially a plastic with a size of 5 mm or less is defined as micro-plastic and are carried by oceancurrents over long distances, causing global pollution. These are not easily decomposed in the natural environment. In this paper,we aimed to experimentally demonstrate that micro-plastics in seawater can be continuously separated by electromagneticArchimedes force. Using polyethylene particles of 3 mm in diameter as the separation target, a flow channel was fabricated andseparation conditions were investigated by particle trajectory calculations for separation experiments. Based on the calculationresults, a solenoid-type superconducting magnet was used as a source of magnetic field to conduct separation experiments of micro-plastics in seawater. Although a high separation rate was assumed in the simulation results, the experimental results did not showany significant improvement in the separation rate due to the electromagnetic Archimedes force. It was found that the gas generatedby the electrolytic reaction may have inhibited the migration of the particles.
Magnetic separation device for paramagnetic materials operated in a low magnetic field
F. Mishima,N. Nomura,S. Nishijima 한국초전도저온학회 2022 한국초전도저온공학회논문지 Vol.24 No.3
We have been developing a magnetic separation device that can be used in low magnetic fields for paramagnetic materials. Magnetic separation of paramagnetic particles with a small particle size is desired for volume reduction of contaminated soil inFukushima or separation of iron scale from water supply system in power plants. However, the implementation of the system hasbeen difficult due to the needed magnetic fields is high for paramagnetic materials. This is because there was a problem in installingsuch a magnet in the site. Therefore, we have developed a magnetic separation system that combines a selection tube and magneticseparation that can separate small sized paramagnetic particles in a low magnetic field. The selection tube is a technique forclassifying the suspended particles by utilizing the phenomenon that the suspended particles come to rest when the gravity actingon the particles and the drag force are balanced when the suspension is flowed upward. In the balanced condition, they can becaptured with even small magnetic forces. In this study, we calculated the particle size of paramagnetic particles trapped in aselection tube in a high gradient magnetic field. As a result, the combination of the selection tube and HGMS (High GradientMagnetic Separation-system) can separate small sized paramagnetic particles under low magnetic field with high efficiency, andthis paper shows its potential application.
F. Mishima,Aoi Nagahama,N. Nomura,S. Nishijima 한국초전도저온학회 2023 한국초전도저온공학회논문지 Vol.25 No.3
Magnetic separation technology for small paramagnetic particles has been desired for the volume reduction of contaminated soil from the Fukushima nuclear power plant accident and for the separation of scale and crud from nuclear power plants. However, the magnetic separation for paramagnetic particles requires a superconducting high gradient magnetic separation system applied, hence expanding the bore diameter of the magnets is necessary for mass processing and the initial and running costs would be enormous. The use of high magnetic fields makes safe onsite operation difficult, and there is an industrial need to increase the magnetic separation efficiency for paramagnetic particles in as low a magnetic field as possible. Therefore, we have been developing a magnetic separation system combined with a selection tube, which can separate small paramagnetic particles in a low magnetic field. In the previous technique we developed, a certain range of particle size was classified, and the classified particles were captured by magnetic separation. In this new approach, the fluid control method has been improved in order to the selectively classify particles of various diameters by using a multi-stage selection tube. The soil classification using a multi-stage selection tube was studied by calculation and experiment, and good results were obtained. In this paper, we report the effectiveness of the multi-stage selection tube was examined.
Fundamental study on gene transfer utilizing magnetic force and jet injector
Hasegawa, T.,Nakagam, H.,Akiyama, Y.,Nishijima, S. The Korea Institute of Applied Superconductivity a 2017 한국초전도저온공학회논문지 Vol.19 No.1
Recently, DNA vaccination is attracting attentions as a new therapeutic method for lifestyle diseases and autoimmune diseases. However, its clinical applications are limited because a safe and efficient gene transfer method has not been established yet. In this study, a new method of gene transfer was proposed which utilizes the jet injection and the magnetic transfection. The jet injection is a method to inject medical liquid by momentary high pressure without needle. The injected liquid diffuses in the bio tissue and the endocytosis is considered to be improved by the diffusion. The magnetic transfection is a method to deliver the conjugates of plasmid DNA and magnetic particles to the desired site by external magnetic field. It is expected that jet injection of the conjugates causes slight membrane disruptions and the traction of the conjugates by magnetic field induces the efficient gene transfer. In conclusion, the possibility of improvement of the gene expression by the combination of jet injection and magnetic transfection was confirmed.