• Journal of the Korean Society of Propulsion Engineers
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• v.19 no.3
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• pp.83-88
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• 2015

Coating materials used in the electron beam (EB) deposition method, which is being studied as one of the fabrication methods of thermal barrier coating, are exposed to high power electron beam at focused area during the EB deposition. Therefore the coating source for EB process is needed to form as ingot with appropriate density and microstructure to sustain their shape and stable melts status during EB deposition. In this study, we tried to find the optimum powder condition for fabrication of ingot of 8 wt% yttria stabilized zirconia which can be used for EB irradiation. It seems that the ingot, which is fabricated through bi-modal type initial powder mixture which consists of tens of micro and nano size particles, was shown better performance than the ingot which is fabricated using monolithic nanoscale powder when exposed to high power EB.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.6
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• pp.797-803
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• 2010

A vehicle door impact beam made of a thin sheet of steel has been constructed using hot stamping technology with the aim of ensuring occupant safety in the event of a side collision. This technology has been used to increase the strength of the vehicle body parts and to reduce the weight of the door impact beam as well as the number of work processes. Mechanical tests were performed to determine the material properties of the hot-stamped specimen and the results of the tests were used as input data in stamping and structural simulation in order to obtain the optimal design of door impact beam. The strength of the hot-stamped door impact beam increased to a value that was 102% higher than that of conventional pipe-shaped door impact beam. A weight reduction of 34% was also achieved.

• Journal of IKEEE
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• v.23 no.3
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• pp.904-909
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• 2019

Using the ion-beam irradiated indium zinc oxide (IZO) films which was cured at $100^{\circ}C$, uniform LC and homogeneous alignment of liquid crystal (LC) molecules was achieved. The IZO film was deposited on the glass substrate at the curing temperature of $100^{\circ}C$ and irradiated by the ion-beam which is an LC alignment method. To verify the LC alignment characteristics, polarizing optical microscope and the crystal rotation method were used. Additionally, it was confirmed that the LC cell with the IZO films had an enough thermal budget for high-quality LC applications. Field emission scanning electron microscope was conducted as a surface analysis to evaluate the effect of the ion-beam irradiation on the IZO films. Through this, it was revealed that the ion-beam irradiation induced rough surface with anisotropic characteristics. Finally, electro-optical (EO) performances of the twisted-nematic cells with the IZO films were collected and it was confirmed that this cell had better EO performances than the conventional rubbed polyimide. Furthermore, the polar anchoring energy was measured and a suitable value for stable LC device operation was achieved.

• Proceedings of the Optical Society of Korea Conference
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• 2000.02a
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• pp.288-289
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• 2000

SBN, BSKNN KNSBN 등의 tungsten-bronze 계열에 속하는 광굴절 결정은 짧은 파장에서 좋은 감광도와 빠른 응답시간을 갖는다. 이중에서도 KNSBN 결정은 큰 크기의 결정 성장 및 도핑이 용이하고 광굴절 결정에서 중요한 특성 중 하나인 열 안정성(thermal stability)이 좋기 때문에 빠른 응답특성이 요구되는 응용분야에서 촉망받는 매질이다. 본 논문에서는 광정보저장, 광정보처리, 광컴퓨터, 광통신과 같은 다양한 분야에서 응용가능성을 가지는 Cu가 0.04wt.%도핑된 5mm$\times$5mm$\times$5mm 크기의 KNSBN 결정을 이용한 광신호의 증폭기술에 대하여 연구하였다. 먼저 Cu-KNSNB 결정의 2광파 결합 특성을 분석하기 위하여, 기록 파장에 따른 지수이득계수의 외부입사각의존성, 최대 지수이득계수를 나타내는 외부입사각에서 입사빔의 세기비에 따른 2광파 결합 이득을 측정하였다. 또한, 632.8nm파장 영역에서 기록 및 삭제시간 상수, 회절 효율의 입사빔 세기비 의존성을 측정하였다. 그리고, 음향-광학 변조기(AOM: acousto-optic modulator)에 의해 진폭 변조된 신호빔을 이용하여 광신호 증폭특성을 분석하고 그 결과를 제시하였다. 이때 두 빔의 입사각은 최대 지수이득계수를 나타내는 입사반각 12$^{\circ}$로 고정하고, 감쇄기를 이용하여 신호빔의 세기를 조절하면서 신호빔의 차동이득을 측정하였다. 투과된 신호빔은 같은 주파수에서 차동 이득(diffrerential gain)을 보였으며, 이는 moving grating과 시간-변조된 신호빔(또는 펌프빔)사이의 새로운 상호작용은 광굴절 결정의 시간 적분 특성에 의한 것이다. (중략) 경우는 상온에서 펌프 펄스의 유지시간이 0.5% 인 경우 레이저가 동작하는 것을 보여주었다. 이는 구조내에서 열전도가 문제가 된다는 것을 의미하는데 위아래가 공기로 둘러 싸여 있어 발생한 열이 가는 유전체 네트웍을 통해서만 전달 될 수 있기 때문이다. (중략)$^4$A$_2$에 의한 nophonon line R$_1$, R$_2$(680.4, 678.5 nm) 및 $^2$T$_1$$\longrightarrow$$^4$A$_2$(655.7, 649.3, 645.2 nm)의 형광방출 스펙트럼을 얻었으며, 형광수명은 0.264 ms로 조사되었다. 제조된 레이저 발진봉은 직경 6.3 m, 길이 45 nm이었다.\pm$0.06kHz Ge $F_4$; -1.84$\pm$0.04kHz$0.04kHz/TEX>0.04kHz 모국어 및 관련 외국어의 음운규칙만 알면 어느 학습대상 외국어에라도 적용할 수 있는 보편성을 지니는 것으로 사료된다.없다. 그렇다면 겹의문사를 [-wh]의리를 지 닌 의문사의 병렬로 분석할 수 없다. 예를 들어 누구누구를 [주구-이-ν가] [누구누구-이- ν가]로부터 생성되었다고 볼 수 없다. 그러므로 [-wh] 겹의문사는 복수 의미를 지닐 수 없 다. 그러면 단수 의미는 어떻게 생성되는가\ulcorner 본 논문에서는 표면적 형태에도 불구하고 [-wh]의미의 겹의문사는 병렬적 관계의 합성어가 아니라 내부구조를 지니지 않은 단순한 단어(minimal $X^{0}$ elements)로 가정한다.

• Proceedings of the KWS Conference
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• 2009.11a
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• pp.107-107
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• 2009

모듈 형 터빈 다이아프람은, 아우터 링(outer ring), 스팀 패스(steam path)와 이너 웹(inner web)의 원형 형상을 갖는 세 부분을 조립하여 원주 방향의 용접 조인트를 형성하는 기존의 다이아프람 형태가 아니라, 아우터 슈라우드(outer shroud), 베인(vane)과 이너 슈라우드(inner shroud)의 세 부분이 하나의 모듈을 이루고 이러한 모듈을 원주 방향으로 조립하여 방사 방향의 조인트를 형성한다. 전자빔 용접은 이와 같은 방사 방향의 조인트를 수직으로 가로지르는 용접 궤적을 따라 진행되며, 용접 패스에 따라 형성되는 용융 비드의 단면적만큼 인접하는 두 모듈을 접합시킨다. 이 경우 용융 비드의 단면적과 형상은 두 모듈의 결합 강도를 결정하는 중요한 요소가 되어, 제작 시 다이아프람의 크기와 두께에 따라 용입 깊이와 평균 단면 비드 폭을 규정하고 있다. 본 연구에서는 용입 깊이와 단면 비드 폭의 요구 조건을 만족하면서 결함이 없는 건전한 용접부를 얻을 수 있는 최적 용접 조건을 도출하는데 그 목적이 있다. 이를 위해 플레이트 시편과 모듈 시편을 사용한 기초 실험과 유사 시제품(semi-mockup) 실험을 실시하였다. 플레이트 기초 실험을 통해 전자빔 주요 변수인 빔 전류, 초점 위치, 용접 속도, 빔 진동 폭 변화에 따른 용융 비드 형상 변화를 관찰하였고, 빔 전류가 용입 깊이에 가장 큰 영향을 주는 인자임을 확인하여 요구 용입 깊이 별 적정 빔 전류 값을 설정하였다. 용접 속도는 생산성 측면에서 균열이 발생하지 않는 범위에서 가능하면 가장 큰 값을 사용하였고, 빔 진동 폭은 초점 위치와 함께 단면 비드 형상 결정에 많은 영향을 주는 인자로 확인되어 균열이 없는 가장 이상적인 단면 비드 형상인 완만한 쐐기 형태가 되도록 설정하였다. 이 후 실제 제품 폭과 용접 패스를 갖는 블록 모듈 실험을 통해 설정 용접 변수의 적용성과 균열 발생 여부를 확인하였고, 이 때 적용 제품 폭이 30 mm 이하이며 요구 용입 깊이가 50 mm 이상의 경우에서 비드 중앙부 균열이 발생함을 관찰하였다. 따라서 해당 영역의 제품에는 균열 저항성이 높도록 용접 속도와 빔 진동 폭을 줄여 최적 용접 변수를 새롭게 설정하였으며, 이를 유사 시제품 실험에 적용하여 최종적으로 용접 변수 안정성을 검증하였다. 이러한 실험을 통해 확인된 최적 용접 조건을 실 제품 제작에 적용하여 모듈 형 터빈 다이아프람 전자빔 용접 제작을 성공적으로 완료할 수 있었다.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.25 no.2
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• pp.175-182
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• 2012

In this paper we are concerned with the performance of structural stability of torsion in square cross section of a beam with holes. The critical load is defined as the smallest load at which the equilibrium of the structure fails to be stable as the load is slowly increased from zero. The beams subjected to torsion are frequently encountered in general structures and these forces influence to the stability of structure. The boundary element method is found to be very efficient and accurate for the analysis of torsion problems including complex boundary conditions with respect to its simplicity and generality. In this paper, it is required to derive the boundary element formulation for torsion problem and integrate directly on the discrete boundary. To investigate the validity of the developed computer program, three distinctly solid cross-sections which are elliptical, rectangular and triangular one are analyzed, and comparisons are made with analytical approaches where these can also be used.

• Journal of the Institute of Convergence Signal Processing
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• v.22 no.3
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• pp.91-98
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• 2021

The installation and performance test of the ISOL (Isotope Separation On Line) system for the generation and separation of Rare Isotopes (RI) beams is in progress at the Rare Isotope Science Project (RISP), Institute for Basic Science (IBS). The various RI beams generated by the ISOL target/ion source go through the beam lines and separators, and only the RI beam desired by the user is selected and transmitted to the superconducting linear accelerator at the downstream of the ISOL. In the ISOL system, two separators are installed to separate a specific RI beam, and control is performed by the Experimental Physics and Industrial Control System (EPICS). In this study, an EPICS IOC (Input-Output Control) was developed to measure the magnetic field of a dipole magnet for mass separation of a multivalent (n+) RI beam in the A/Q separator, which is one of the ISOL RI beam separators. The operational stability of the A/Q separator was tested through a magnetic field measurement using a Hall probe.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.37 no.7
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• pp.36-42
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• 2000

Some polarization characteristics of reflection type photopolymer are investigated. Photopolymer on a Mylar substrate alters an incoming linearly polarized laser beam to an elliptical polarization. Due to the rotation of the polarization, the recording gratings show different diffraction efficiencies. The rotation angle is of order of 10-50% for the tested samples. It is found that the polymer layer does not changes the polarization direction but the Mylar substrate alone distorts the incoming polarization to a comparable degree. As align the polarization states of photopolymers to be parallel with a laser using a He-Ne laser(633nm), which is not sensitive to that material, it was possible to make high diffraction efficiency gratings.

• Analytical Science and Technology
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• v.14 no.3
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• pp.203-211
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• 2001

In this paper it was described on the intereference effect of uranium to analyze Cs in $UO_2$ by Electron Probe Micro Analysis(EPMA) and the beam stability of Cs $L_{\alpha}$ X-ray intensity for some Cs compounds. According to the experimental results, the CsI showed the highest $L_{\alpha}$ X-ray intensity among the tested Cs compounds at the experimental condition; 15~30 kV of accelerating voltage and PET, LiF crystal. When 100 nA of beam current was applied to Cs compounds, Cs $L_{\alpha}$ X-ray intensity was continuously decreased with increasing time. The decreasing rate of Cs $L_{\alpha}$ X-ray intensity was directly proportional to the applied beam current and accelerating voltage but inversely proportional to the applied beam size. It was found that uranium interference can be prevented by using Cs $L_{\alpha}$ X-ray wavelength of Lif crytal for Cs analysis in $UO_2$ by EPMA.

• The Journal of the Convergence on Culture Technology
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• v.6 no.4
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• pp.727-732
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• 2020

In this paper, when a refractive index grating and a gain grating were simultaneously present in a DFB laser having a wavelength of 1.55 ㎛, a dielectric film coating was applied so that reflection did not occur on the right mirror surface, so that 𝜌_r=0. In case of δL > 0, the threshold gain and the beam distribution in the longitudinal direction and the radiated power ratio P_l/P_r of the oscillation mode were compared for the cases of the phase of 𝜌_l=π and π/2. If the phase of 𝜌_l=π, in order to obtain a low threshold current and high frequency stability, κL should be greater than 8. In the case of the phase of 𝜌_l= π/2, when κL is larger than 4.0, the oscillation gain starts to be lower than when the phase of 𝜌_l=π. In order to lower the threshold current of a oscillation mode and enhance the frequency stability, κL should be greater than 8.