• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.231.1-231.1
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• 2014

열 플라즈마(thermal plasma) 는 저온 플라즈마(cold plasma)와 달리 이온과 전자와 중성입자들이 충분한 에너지 교환으로 인해 열평형 상태를 가진다. 열 플라즈마를 생성 시킬 때 전극 사이에서 아크방전을 시켜 제트 형태로 플라즈마를 발생시키는 것을 플라즈마 토치(plasma torch)라고 한다. 이러한 플라즈마 토치는 화학 원소 분해, 강판 절단, 유해 기체 분해 등으로 널리 사용되고 있다. 본 연구에서는 플라즈마 토치를 수치적으로 해석하여 플라즈마의 특성을 알아보았다. 수치해석적 접근방법으로 열 플라즈마는 LTE (local thermodynamic equilibrium)을 가정하였으며 one-fluid 이론을 적용하였다. 이때 사용된 코드는 DCPTUN으로서 $C^{+}^{+}$로 작성된 열플라즈마 유동의 특성해석 코드인 동시에 SIMPLE 알고리즘을 이용한 유체 코드이다. 시뮬레이션은 2차원 축대칭이며 정렬격자계 및 비정렬격자계 모두에서 사용이 가능하도록 되어있다. 또한 맥스웰 방정식을 통해 electromagnetic field를 풀도록 하여 RF 시뮬레이션이 가능하도록 하였다. 이와 같은 열 플라즈마 시뮬레이션을 통해서 플라즈마 토치의 특성을 알아보았다.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.15 no.4
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• pp.321-332
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• 2017

In order to build a general model of a high-throughput uranium electrorefining process according to the electrode configuration, numerical analysis was conducted using the COMSOL Multiphysics V5.3 electrodeposition module with Ordinary Differential Equation (ODE) interfaces. The generated model was validated by comparing a current density-potential curve according to the distance between the anode and cathode and the electrode array, using a lab-scale (1kg U/day) multi-electrode electrorefiner made by the Korea Atomic Energy Research Institute (KAERI). The operating temperature was $500^{\circ}C$ and LiCl-KCl eutectic with 3.5wt% $UCl_3$ was used for molten salt. The efficiency of the uranium electrorefining apparatus was improved by lowering the cell potential as the distance between the electrodes decreased and the anode/cathode area ratio increased. This approach will be useful for constructing database for safety design of high throughput spent nuclear fuel electrorefiners.

• Korean Journal of Optics and Photonics
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• v.14 no.2
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• pp.122-129
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• 2003

In the case of a AIGalnP/GaP system rectangular parallelepiped high brightness LED which has side walls etched to be slanted off the vertical direction, we have studied the effects of lossy electrodes and material absorption and etching depth and angle of side walls on its light extraction efficiency. If LEDs have no electrodes, in order to obtain an 80％ light extraction efficiency of a TIP (truncated inverted pyramid) LED, the side-etched LEDs should have an etching angle of 22$^{\circ}$~45$^{\circ}$ and an etching depth of 8~17% of a dice height and an absorption coefficient less than 1 $cm^{-1}$ / In case of etching depth of 16~39% of a dice height, we can obtain a 90% light extraction efficiency of a TIP LED. But when LEDs have two electrodes and no absorption loss, in order to obtain an 80％ light extraction efficiency of a TIP LEBs, the side-etched LEDs should have an etching angle of 25$^{\circ}$-45$^{\circ}$ and an etching depth of 30～36% of a dice height. In case of etching depth of 57~71％ of a dice height, we can obtain a 90％ light extraction efficiency of a TIP LED.

• Journal of the Korean Electrochemical Society
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• v.22 no.4
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• pp.139-147
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• 2019

Lithium-ion battery (LiB) with high energy density and efficiency has been utilized for the electric vehicle (EV) and energy storage system (ESS) as well as portable devices. However, as explosion accidents have frequently happened till lately, all-solid-state lithium secondary battery (ALSB) began to get in a spotlight because it can secure a very high safety and energy density by substituting flammable organic liquid electrolyte to nonflammable inorganic solid electrolyte. In spite of ALSB's certain merits, it has shown much poorer performance of cells than one of LiB due to some challenges, which have been small or never dealt with in the LiB system. Hence, although plenty of studies made progress to solve them, an approach about design of all-solid-state electrode (ASSE) has been limited on account of difficulty of ALSB's experiments. That is why the virtual 3D structure of an all-solid-state electrode has to be built and used for the prediction of cell performance. In this study, we elucidate how to form the 3D ASSE structure and what to be needed for the simulation of characteristics on ALSB. Furthermore, the ultimate orientation of 3D modeling and simulation for the study of ALSB are briefly suggested.

• Korean Journal of Optics and Photonics
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• v.7 no.3
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• pp.260-265
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• 1996

In this paper, we studied effects of active-passive interface on the tuning characteristics of a multielectrode DBR laser. An abrupt interface distorts the threshold gain and the phase change in a multielectrode DBR laser, which results in narrowing of the continuous tuning range. On other hand, an interface with the gradual index change gives tuning characteristics which is very similar to that obtained by ignoring the interface.

• Journal of Welding and Joining
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• v.8 no.1
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• pp.62-69
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• 1990

Being focused on the recent studies that the fatigue strength of resistance spot weldmentes can be improved by using ellipsoidal weld nuggets, the voltage and temperature distribution in resistance spot weldments were simulated for the various rectangular electrodes which had the different aspect ratio of the contact area. Because the electrode shape was not axi-symmetric, the solution domain for simulation should be three dimensional. A series of experiments were carred out to verify the analytically obtained temperature distribution in the weldment. From the calculational and experimental results, it could be revealed that the nugget took the form of ellipsoid, while both results showed a considerable discrepancy for the high aspect ratio.

• Proceedings of the KIEE Conference
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• 2006.10d
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• pp.37-39
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• 2006

본 연구에서는 상변화소자의 구조 변화에 따른 열전달 현상과 reset 전류에 대한 시뮬레이션을 실행하였다. 상변화소자의 상변화재료의 profile에 따른 주울열의 발생 및 reset 전류의 변화량을 시뮬레이션 한 결과, 하부전극에서부터 도포되는 상변화재료 박막의 두께가 2000[A]인 경우는 541($^{\circ}C$)로 현저하게 발열온도가 낮아지는 것을 알 수 있다. 이는 저항체로 쓰이는 상변화재료의 저항 감소로 인해 발열량이 적게 되고 상변화재료를 통해 전달된 열이 상부전극 텅스텐과 접촉하면서 외부로 쉽게 전달되면서 빠져나감에 따라 온도가 많이 올라가지 않는 것으로 생각된다.

• KSBB Journal
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• v.4 no.2
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• pp.150-156
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• 1989

The chaacterisitics of a commercial membrance-coverd electrode in air-saturated saline solution were investigated in terms of a steadystate one-dimensional model. The electrode system miiersed in an aqueous medium consists of three layers: an external concentration boundary layer, a membrance, and an inner electrolyte layer. The membrance can be permeabld to the water and impermeable to the ionic species. In stationary midium, the water migrates from the external medium to the inner electrolyte layer until a thermodynamic equilibrium is reached. In a following midium, however, there is a reverse direction of water movement due to the hyrodynamic pressure differential until both thickness of the electrolyte layer and the membrance are equal.

• Journal of computational fluids engineering
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• v.15 no.4
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• pp.40-45
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• 2010

The flow rate is higher in ACEO micro-pumps with step electrodes than in micro-pumps with planar asymmetric electrodes. In the present study, numerical simulations were made of a ACEO micro-pump with step electrodes to investigate the effects of electrode design parameters on the pumping flow rate. The electrical charge at the electrodes, the fluid flow, and potential were solved, taking into account the finite size of ions, that is, the steric effect. This effect is recognized to be capable of quantifying the electrical charge more accurately in the electrical double layer subject to high voltages. Geometrical parameters such as heights, widths, and gaps of three-dimensional electrodes were optimized to enhance the pumping flow rate. Moreover, the effect of amplitude and frequency of AC was studied.

• Journal of the Korean Electrochemical Society
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• v.2 no.1
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• pp.13-16
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• 1999

A mathematical analysis of bipolar electrode reactor model for complex electrochemical reactions could estimate total current from time-concentration data, which coincided well with experimental total current data. Thus behaviour of bipolar electrode reactor could be described by a proposed simulation model. This paper demonstrates how such a model can be used a useful tool in the design for pilot plant experimentation.