• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.21 no.4
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• pp.381-387
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• 2008

Neutron production rate in spherically convergent beam fusion(SCBF) device as a portable neutron source strongly depends on the ion current and the grid cathode structure. In this paper, as the process of design and analysis, Design of Experiment(DOE) based on the results by Finite Element Method-Flux Corrected Transport(FEM-FCT) method is employed to calculate the ion current. This method is very useful to find optimal design conditions in a short time. Number of rings, radius of rings, and distance between the grid cathode and center are selected as control factors. From the results in the optimized model, the higher ion current is calculated and deeper potential well is also observed.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.250.1-250.1
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• 2014

A multicusp ion source has been used widely in negative hydrogen cyclotrons mainly for radioisotope productions. The ion source is designed to have cusp geometries of magnetic field inside plasma chamber, where ions are confining and their mean lifetimes increase. The magnetic confinement produced a number of permanent magnetic poles helps to increase beam currents and reduce the emittance. Therefore optimizing the number of magnets confining more ions and increasing their mean lifetime in plasma has to be investigated in order to improve the performance of the ion source. In this work a numerical simulation of the magnetic flux density from a number of permanent magnets is carried to optimize the cusp geometries producing the highest plasma density, which is clearly indicated along the full-line cusp geometry. The effect of magnetic fields and a number of poles on the plasma structure are investigated by a computing tool. The electron confinement effect becomes stronger and the density increases with increasing the number of poles. On the contrary, the escape of electrons from the loss cone becomes more frequent as the pole number increases [1]. To understand above observation the electron and ion's trajectories along with different cusp geometries are simulated. The simulation has been shown that the optimized numbers of magnets can improve the ion density and uniformity.

• Membrane Journal
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• v.20 no.2
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• pp.151-158
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• 2010

This paper presents the synthesis of ampholyte immobilized hollow-fiber membranes and adsorption characteristic of metallic ions. This is prepared by radiation induced grafting polymerization of an epoxy group containing Glycidyl methacrylate (GMA) onto an existing polyethylene porous hollow-fiber membrane. Ampholyte ion-exchanged alkalic group, $-NH_2$ (amine function) of Taurine (TAU) is reacted with glycidyl of GMA for the synthesis of stable membrane. However, Sodium sulfite (SS) membrane is also prepared by making chemical bonds with GMA of porous hollow-fiber membrane for the comparison of adsorption characteristic of metallic ions. These are called as TAU and SS membranes, respectively. It is shown that TAU membrane shows a steady flux, 0.9 m/h regardless of the density of TAU, while the flux of SS membrane decreases rapidly as the density of $SO_3H$ group increases. SS membrane showed a negligible flux. TAU membrane with the density 0.8 mmol/g shows the amount of metallic ions adsorbed in the following order, Cu > Cd > Mg > Sb > Pb. In general, TAU membrane with high density and reaction time showed the high amount of metallic ions adsorbed and flux.

• Journal of the korean society of oceanography
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• v.31 no.2
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• pp.55-63
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• 1996

Distribution of suspended particulate matter, dissolved oxygen and major inorganic nutrients along a meridional section ($126^{\circ}$ 33' E) in the Cheju Strait is described along with the hydrographic and current data obtained during April 25-27, 1995. The current measurements was conducted using a vessel-mounted Acoustic Doppler Current Profiler (ADCP). Repeated coverage along an ADCP transect during 25 hours allows to calculate the daily mean along- and cross-strait currents. Measured material concentrations and the mean current speed were used to estimate the flux density (cencentration times current speed) of materials. Two types of depth distibution of flux densities were observed. for nitrate and suspended particulate matter, the depth distribution pattern of materials determines those of flux densities. However, flow patterns determine those of flux densities for dissolved oxygen, phosphate and silicic acid. The total along-strait water volume transport is about 0.3 Sv (1Sv $10^{6}$ $m^{3}/s^{-1}$). The total along-strait material transports are estimated to be 3.1 $${\times} $10^{5}$ $g/s^{-1},$ 2.4 ${\times}$ $10^{6}\;g/s^{-1},$ 7.I ${\times}$ $10^{2}\;mol/s^{-1},$ 3.I ${\times}$ $10\;mol/s^{-1},$ 1.7 ${\times}$ $10^{3}\;mol/s^{-1}$ for suspended particulate matter, dissolved oxygen, nitrate ion, silicic acid and phosphate ion, respectively.

• Transactions of the Korean hydrogen and new energy society
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• v.16 no.2
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• pp.136-141
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• 2005

Li-doped NiO was synthesized by molten salt method. $LiNO_3$-LiOH flux was used as a source for Li doping. $NiCl_2$ was added to the molten Li flux and then processed to make the Li-doped NiO material. Li:Ni ratios were maintained from 5:1 to 30:1 during the synthetic procedure and the Li doping amount of synthesized materials were found between 0.086-0.190 as a Li ion to Ni ion ratio. Li doping did not change the basic cubic structural characteristics of NiO as evidenced by XRD studies, however the lattice parameter decreased from 0.41769nm in pure NiO to 0.41271nm as Li doping amount increased. Hydrogen gas sensors were fabricated using these materials as thick films on alumina substrates. The half surface of each sensor was coated with the Pt catalyst. The sensor when exposed to the hydrogen gas blended in air, heated up the catalytic surface leaving rest half surface (without catalyst) cold. The thermoelectric voltage thus built up along the hot and cold surface of the Li-doped NiO made the basis for detecting hydrogen gas. The linearity of the voltage signal vs $H_2$ concentration was checked up to 4% of $H_2$ in air (as higher concentrations above 4.65% are explosive in air) using Li doped NiO of Li ion/Ni ion=0.111 as the sensor material. The response time T90 and the recovery time RT90 were less than 25 sec. There was minimum interference of other gases and hence $H_2$ gas can easily be detected.

• Journal of Korean Vacuum Science & Technology
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• v.6 no.2
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• pp.55-57
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• 2002

Metal-vapor-vacuum-arc ion source is an ideal source for both high current metal ion implanter and high current plasma thin-film deposition systems. It uses the direct evaporation of metal from surface of cathode by vacuum arc to produce a very high flux of ion plasmas. The MEVVA ion source, the high-current metal-ion implanter and high-current magnetic-field-filtered plasma thin-film deposition systems developed in Beijing Normal University are introduced in this paper.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1997.04a
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• pp.172-176
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• 1997

It is likely that the corona discharge appears due to the motion and the multiplication of electron and ion under the nonuniform electric field. Because the motion and the multiplication of electron and ion are the function of electric field, for the simulation of the corona discharge, we have to calculate the electric field, before the calculation of the motion and the multiplication of electron and ion. In this paper, the electric field is calculated on the assumption that the gap between a hyperboloidal needle and a plane is 1-dimension, and the motion and the multiplication of electron and ion are determined by Flux-Corrected Transport method. For this purpose, we solve the electron and ion continuity equation together with Poisson equation. We calculated the current density and the electron and ion density distributions between electrodes as well as electric field distortion due to the space charge assuming that the discharge channel radius is 100${\mu}{\textrm}{m}$. In this simulation, it is found that the current density has one peak as observed by experiment, and electric field distortion is important to the formation and the stability of the corona discharge.

• Journal of Applied Biological Chemistry
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• v.43 no.1
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• pp.18-24
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• 2000

A one-dimensional transport of displacing monovalent ion, $A^+$, and a trivalent ion being displaced, $B^{3+}^ in a porous exchange system such as soil was approximated using the Crank-Nicolson implicit finite difference technique and the Thomas algorithm in tandem. The variations in the concentration profile were investigated by varying the ion-exchange equilibrium constant (k) of ion-exchange reactions, the influent concentrations, and the cation exchange capacity (CEC) of the exchanger, under constant flux condition of pore water and dispersion coefficient. A higher value of k resulted in a greater removal of the native ion, behind the sharper advancing front of displacing ion, while the magnitude of the penetration distance of $A^+$ was not great. As the CEC increased, the equivalent fraction of $B^{3+}^ initially in the soil was greater, thus indicating that a higher CEC adsorbed trivalent cations preferentially over monovalent ions. Mass balance error from simulation results was less than 1%, indicating this model accounted for instantaneous charge balance fairly well.

• Nuclear Engineering and Technology
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• v.56 no.2
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• pp.546-551
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• 2024

As an effective methods of plasma heating, neutral beam injection (NBI) systems based on negative hydrogen ion sources will be utilized in future magnetic-confinement nuclear fusion experiments. Because of the collisions between the fast negative ions and the neutral background gas, the positive ions are inevitable created in the acceleration region in the negative NBI system. These positive ions are accelerated back into the ion source and become high energy backstreaming ions. In order to explore the characters of backstreaming ions, the track and power deposition of backstreaming H⁺ beam is estimated using the experimental and simulation methods at NNBI test facility. Results show that the flux of backstreaming positive ions is 1.93 % of that of negative ion extraction from ion source, and the magnet filed in the beam source has an effect on the backstreaming positive ions propagation.

• Proceedings of the Korea Concrete Institute Conference
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• 1999.04a
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• pp.160-165
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• 1999

Osmotic pressure induced by semi-permeability of hardened cement pasts and cement mortar was studied, which was considered to be a cause of failure such as separation and blistering of floor coatings or wall coatings from the concrete substrate. The specimens with a water cement ratio of 45, 60 and 75% were installed between the solution of sodium chloride and distilled water. First, we measured water flux from distilled water to sodium chloride and the ion flux of Na+ and Cl- through the specimens. Then, we measured osmotic pressure induced by semi-permeability of the specimens using an apparatus which was specially developed for this study. It was made clear that hardened cement paste and cement mortar have properties of semipermeability, and the osmotic pressure is closely related to their water cement ratio. Finally, we calculated the osmotic pressure according to Staverman's equation, which was obtained for organic membranes, and tried to explain quantitatively the observed pressure.