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

• The Korean Journal of Ceramics
• /
• v.6 no.2
• /
• pp.129-133
• /
• 2000

Boron nitride films were synthesized with $N_2$ion flux of low energy, up to 100 eV, at different substrate temperatures of no heating, 200, 400, 500, and $800^{\circ}C$, respectively. Boron was supplied by e-beam evaporation at the rate of $1.5\AA$/sec. For all the conditions, hexagonal BN (h-BN) phase was mainly synthesized and high resolution transmission electron microscopy (HRTEM) showed that (002) planes of h-BN phase were aligned vertical to the Si substrate. The maximum alignment occurred around $400^{\circ}C$. In addition to major h-BN phase, transmission electron diffraction (TED) rings identified the formation of cubic BN (c-BN) phase. But HRTEM showed no distinct and continuous c-BN layer. These results suggest that c-BN phase may form in a scattered form even when h-BN phase is mainly synthesized under small momentum transfer by bombarding ions, which are not reconciled with the macro compressive stress model for the c-BN formation.

• Journal of Korean Society of Occupational and Environmental Hygiene
• /
• v.10 no.1
• /
• pp.32-44
• /
• 2000

The practice of welding stainless steel is known to produce various valance states of chromium. $CO_2$ flux cored arc welding on stainless was performed in fume collection chamber. Content of total chromium and hexavalent chromium in fumes, content of hexavalent chromium in total chromium, solubility of hexavalent chromium were investigated. Content of total chromium in fumes increases from 2~3% to 7~9% as a function of input energy, but hexavalent chromium, less than 1.2% in fumes, is not related to input energy. Hexavalent chromium in fumes exists as solubles up to 90%. Content of total chromium in flux cored arc welding fumes and solubility of hexavalent chromium are similar to shielded metal arc welding fumes, but content of hexavalent chromium is similar to metal inert gas welding fumes. These characteristics are relevant to flux of wires and $CO_2$ shielding gas.

• Journal of Advanced Marine Engineering and Technology
• /
• v.21 no.4
• /
• pp.437-442
• /
• 1997

An experimental study was carried out in a channel cavity with square heat surface by visual¬ization equipment with Mach - Zehnder interferometer and laser apparatus. The image processing system consists of one commercial image board slit into a personal computer and 2-dimensional sheet light by Argon-Ion Laser with cylindrical lens and flow picture recording system. Instant simultaneous velocity vectors at whole field were measured by 2-D PIV system which adopted two¬frame grey-level cross correlation algorithm. Heat source was uniform heat flux(o.4W/cm$^2$, , O.8W/cm$^2$, 1.2W/cm$^2$). Obtained result showed various flow patterns such as kinetic energy distribution. Severe unsteady flow fluctuation within the cavity are remarkable and sheared mixing layer phenomena are also found at the region where inlet flow is collided with the counter-clockwise rotating main primary vortex. Photographs of Mach ~ Zehnder are also compared in terms of constant heat flux.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
• /
• v.4B no.4
• /
• pp.157-169
• /
• 2004

Motor & generator operation at widely variable speeds is needed in various applications but hybrid and electric vehicle (HEV) stand out today, as quite a few companies are launching this year their mass production of HEVs. The quest for better starter-generators is far from ended, though. The present review paper unfolds a comparative critical evaluation of various starter-generators and their control for HEV. Induction, interior PM synchronous, transverse-flux PM synchronous, switched reluctance, together with claw-pole and biaxial excitation PM synchronous (BEGA) configurations with their control are all considered in system evaluations.

• Polymer(Korea)
• /
• v.39 no.2
• /
• pp.317-322
• /
• 2015

Salinity gradient power is a system which sustainably generates electricity for 24 hrs, if the system is constructed at a certain place where both seawater and river water are consistently pumped. Since power is critically determined by the water flux and the salt rejection, a membrane of water-semipermeable aquaporin protein in cell membranes was studied for pressure-retarded osmosis. NaCl was used as a salt, and $NaNO_3$ was used as a candidate to check the ion selectivity. The water flux of biomimetic aquaporin membranes was negligible at a concentration below 2M. Also, there is no remarkable dependence of water flux and ion selectivity on concentrations higher than 3M. Therefore, the biomimetic aquaporin membrane could not be applied into pressure-retarded osmosis; however, if a membrane could overcome the current limitations, the properties shown by natural cells could be accomplished.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.11 no.5
• /
• pp.231-237
• /
• 2001

Etch rates up to 120 nm/min for $Ta_{2}O_{5}$ were achieved in both $SF_{6}/Ar$ and $Cl_{2}/Ar$ discharges. The effect of ultraviolet (UV) light illumination during ICP etching on $Ta_{2}O_{5}$ etch rate in those plasma chemistries was examined and UV illumination was found to produce significant enhancements in $Ta_{2}O_{5}$ etch rates most likely due to photoassisted desorption of the etch products. The effects of ion flux, ion energy, and plasma composition on (Ba, Sr)$TiO_3$ etch rate were examined and maximum etch rate ~90 nm/min was achieved in $Cl_{2}/Ar$ ICP discharges while $CH_{4}/H_{2}/Ar$ chemistry produced extremely low etch rates (${\leq}10\;nm/min$) under all conditions.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2013.02a
• /
• pp.376-377
• /
• 2013

반도체산업이 발전함에 따라 패턴이 점점 더 복잡해 지고 있다. 이에 따라 웨이퍼 위에 올려지는 layer도 개수도 많아지고 점점 더 두꺼워진다. 예전에는 수백 nm였지만 최근에는 um단위까지 두꺼워지고 있다. 하지만 mask 역할을 하는 ACL과 substrate (SiO2)의 selectivity는 일정하기 때문에 mask 역할을 하는ACL layer 역시 두꺼워지는 것이 불가피하다. 이로인해 예전에는 없었던 문제들이 발생하기 시작한다. Mask 역할을 하는 ACL layer가 얇고 패턴 크기가 클 때에는 아무런 문제도 없었지만 ACL layer도 두꺼워 지고 패턴 크기도 수십 nm로 작아졌기 때문에 ACL 역시 식각 공정을 할 때 어려움이 생기기 시작한다. 이를 해결하기 위한 하나의 방법으로 자화된 ICP 챔버 substrate에 Dual bias frequency 인가하여 식각해 보고 이와같이 하였을 때 식각특성을 분석해 보았다. 자화된 ICP 챔버에서 substrate에 dual bias frequency를 인가함으로써 ion energy와 ion flux에 변화가 생기게 되고 이로 인해 다른 식각 특성이 나타나게 되었다. Dual bias frequency의 비율을 변화시켜 보고 변화에 따른 식각 특성을 분석해 보았다. 이와 같은 과정을 통하여 높은 주파수와 낮은 주파수의 각각의 변화에 따른 식각특성의 변화에 대한 이해를 할 수 있었다.

• Korean Chemical Engineering Research
• /
• v.57 no.3
• /
• pp.338-343
• /
• 2019

The water transport and water content of the electrolyte membrane greatly affect the performance of the membrane in PEMFC(Proton Exchange Membrane Fuel Cell). In this study, the parameters (electroosmotic coefficient, water diffusion coefficient) of polymer membranes for water transport were measured by a simple method, and water flux and ion conductivity were simulated by using a model equation. One dimensional steady state model equation was constructed by using only the electro-osmosis and diffusion as the driving force of water transport. The governing equations were simulated with MATLAB. The electro-osmotic coefficient of $144{\mu}m$ thick polymer membranes was measured in hydrogen pumping cell, the value was 1.11. The water diffusion coefficient was expressed as a function of relative humidity and the activation energy for water diffusion was $2,889kJ/mol{\cdot}K$. The water flux and ion conductivity results simulated by applying these coefficients showed good agreement with the experimental data.

• Proceedings of the KOSOMBE Conference
• /
• v.1998 no.11
• /
• pp.239-240
• /
• 1998

DTET(Dual Transcutaneous Energy Transmission System) is the stable power transferring unit for TAH(Total Artificial Heart) which uses more power than any other artificial organ. It has better efficiency and safety than an ordinary single TET. By reducing the load, it can reduce the change of supplying current for each single TET and it causes the lower change of efficiency. The increment of magnetic flux in coils enables delivering power through thick skin. It can enable internal batteries remove when will be used in a failure of TET, for a lithium ion battery has heavier weight than TET. A DTET should be studied the effect between each coils that generate magnetic flux. It should be compared the advantage with the weakness when it is used.