• 한국진공학회:학술대회논문집
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• 한국진공학회 2011년도 제40회 동계학술대회 초록집
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• pp.300-300
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• 2011

Si oxidation is a key process in developing silicon devices, such as highly integrated metal-oxide-semiconductor (MOS) transistors and antireflection-coating (ARC) on solar cell substrate. Many experimental and theoritical studies have been carried out for elucidating oxidation processes and adsorption structure using ab initio total energy and electronic structure calcultaions. However, the initial oxidation processes at step edge on vicinal Si surface have not been studied using the ReaxFF reactive force field. In this work, strucutural change, charge distribution of oxidized Si throughout the depth from Si surface were observed during oxidation processes on vicinal Si(001) surface inclined by $10.5^{\circ}$ of miscut angle toward [100]. Adsorption energys of step edge and flat terrace were calculated to compare the oxidation reaction at step edge and flat terrace on Si surface.

• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2014년도 추계학술대회 논문집
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• pp.185-185
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• 2014

In this study, we investigated surface characteristics of hydroxyapatite coated surface on nano/micro pore structured Ti-35Ta-xNb alloys. This paper was focus on morphology and corrosion resistance of Anodic oxidation. To prepare the samples, Ti-35Ta-xNb (x= 0, 10 wt. %) alloys were manufactured by arc melting and heat-treated for 12 h at $1050^{\circ}C$ in Ar atmosphere at $0^{\circ}C$ water quenching. Micro-pore structured surface was performed using anodization with a DC power supply at 280 V for 3 min, nanotube formed on Ti-35Ta-xNb alloys was performed using DC power supply at 30 V in 60 min at room temperature. Surface morphology and structure were examined by field-emission scanning electron microscopy, energy-dispersive X-ray spectroscopy and X-ray diffraction.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 1996년도 특별강연 및 추계학술발표 개요집
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• pp.148-152
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• 1996

A transient two-dimensional (2D) model was developed for investigating the heat and fluid flow in old pools and determining velocity profile and temperature distribution for the Gas Metal Arc (GMA) welding process. The mathematical formulation deals with the driving farces (electromagnetic, buoyancy, surface tension and plasma drag forces) as well as energy exchange between the molten filler metal droplet and weld pools. A general thermofluid-mechanics computer program, PHOENICS, was employed to numerically solve the governing equation with the associated source terms. The results of computation have shown that the electromagnetic and surface tension farces as will as the molten filler metal droplet have major influence in shaping the weld pool geometry.

• Journal of Welding and Joining
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• 제35권2호
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• pp.30-34
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• 2017

The trend of the plasma cutting and laser cutting technology of metal alloys including high strength steel, aluminum alloys for the welding structures has been studied. The high-precision plasma systems offer a denser, higher energy arc that in effect produces a sharper cutting tool and high quality cutting products. The high-quality fiber laser systems with compact design and easy set-up make it ideal for cutting in the pipeline or steel structre manufacturing. This paper covers the scientometric analysis of the high efficient cutting technology which are based on the published research works in the 'plasma and laser', and 'cutting technology' obtained from Web of Science, and deals with the details of the background data of the plasma cutting and laser cutting technology.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2004년도 추계학술대회 논문집
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• pp.646-651
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• 2004

Crashworthy design of a train is a systematic approach to ensure the safety of passengers and crews in railway transportation for the prescribed accident scenarios. This approach needs new structural arrangements and designs to absorb higher levels of impact energy in a controlled manner and interior designs to minimize passenger injuries. In this paper, crashworthy design approach is applied to the tilting train express (TIX) design which is newly being developed. Based on a head-on collision and a level crossing collision scenarios, the crash behaviors of a TTX design candidate arc evaluated numerically using the finite element method. Finally, design alternatives which show better crashworthy performances are proposed and verified through the full-rake collision simulations.

• 전기의세계
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• 제29권6호
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• pp.344-348
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• 1980

$SF_{6}$가스의 절연파괴특성 및 화학적특성에 관한 것을 종합해보면, 첫째, $SF_{6}$의 방전은 1개의 전자 avalanche중의 전자수가 임계치 Norit가 $10^{8}$정도에서 streamer에의 전이가 일어나므로서 이루어지며, 둘째, $SF_{6}$의 (.alpha.-.eta.)/.rho.와 E/.rho.의 관계는 .alpha.=.eta.근방에서 직선으로 상승되어 절연파괴에 극히 중요한 뜻을 가지며, 셋째, 두번째의 .alpha.=.eta.에 있어서의 구배는 보통의 기체보다 수 10배크기 때문에 최대전계를 부여하는 전극근방만이 공극의 방전개시를 지배하며, 넷째, 전기기구에 있어서 $SF_{6}$가스의 화학적변화의 energy원으로서는 arc, corona, 열을 들 수 있으며 특히 $SF_{6}$가스중과 공기중과의 내 Corona성을 구하기 위한 인가전압일내 Corona수명시간은 $SF_{6}$가스중이 공기중보다 길다는 것이다.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• 제11B권2호
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• pp.9-14
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• 2001

Because salient pole rotor type single phase SRM(Switched Reluctance Motor) has a simple structure and can be use both radial and axial direction magnetic flux at the same time, its output power per unit volume is high. Therefore, the shaft length can be minimized when compared with same output motors. However, salient pole rotor is hard to design due to its complex magnetic circuit. In this paper, salient pole rotor type single phase SRM with minimized shaft length is designed and selected the most suitable dimension of rotor, stator, pole arc and salient pole.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• 제11B권2호
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• pp.1-8
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• 2001

This paper deals with magnetic field analysis and computation of cogging torque using an analytical method in Interior Permanent Magnet Motor (IPMM). The magnetic field is analyzed by solving space harmonics field analysis due to magnetizing and the cogging torque is analyzed by combining field analysis with relative permeance. In reducing cogging torque, the inferences of various design variable and magnetizing distribution are investigated. It is shown that the slot and pole ratio (the pole-arc / pole-pitch ratio) combination has a significant effect on the cogging torque and presents a optimal flux barrier shape to reduce the cogging torque. The validity of the proposed technique is confirmed with 2-D Finite Element(FE) analysis.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• 제2B권4호
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• pp.156-161
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• 2002

This paper proposes an optimized universal motor for improving its performance using the finite element method (FEM) with the (1＋1) Evolution Strategy (ES) algorithm. To do this, various design parameters are modified, such as air gap length, shape of motor slot, pole shoe, pole width, and rotor shaft diameter. Two parameters (arc length of stator pole and thickness of pole shoe) are chosen and optimized using the program, and the optimized model is built and tested with a performance measuring system. The measured values of the model are compared with those of the initial and the optimized model to prove the algorithm. As a result, the final model improves its performance compared with those of the initial model.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 하계학술대회 논문집 B
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• pp.939-941
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• 2003

High Speed permanent magnet machines are currently being developed for a number of applications including gas turbine power plants, air conditioning systems, machine tools, gas pumps, high performance vacuum pumps, flywheel energy storage systems, aircraft fuel pumps, and so on. Using a high-speed machine eliminates the necessity of the mechanical gearbox and could certainly increase the system efficiency and reduce the total cost. In addition, a high-speed machine has the advantage of small dimension and low weight, i.e. low weight to power and volume to power ratio. This paper presents a review of some important applications (mostly still under development) where high-speed machines arc used, highlighting the advantages of the technology in each case.