• 대한기계학회논문집
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• 제16권12호
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• pp.2205-2215
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• 1992

본 연구에서는 동 베어링에 대한 해석을 바탕으로 원주방행 급유홈 프로팅링 저널베어링으로 지지된 탄성 회전체의 안정성에 대한 이론을 전개함과 동시에 실험을 통해 동 베어링의 안정성을 조사하고자 한다.

• 한국안전학회지
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• 제19권1호
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• pp.94-101
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• 2004

In this study, composite laminated conical shells with ring stiffeners are analyzed. A versatile 4-node shell element which is useful for the analysis of conical shell structures is used. An improved flat shell element is established by the combined use of the addition of non-conforming displacement modes and the substitute shear strain fields. The proposed element has six degrees of freedom per node and permits an easy connection to other types(beam element) of Optimum location and optimum section properties of ring stiffeners are obtained. It is shown that the thickness of conical shell is reduced about 20% by optimum ring stiffeners.

• 한국전자파학회논문지
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• 제20권4호
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• pp.351-356
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• 2009

본 논문에서는 GPS와 위성 DMB에 사용할 수 있는 이중 모드 annular ring 패치 안테나를 제안하였다. 제안된 안테나는 커플링 급전과 annular ring 패치의 네 개의 슬롯을 특징으로 한다. 급전 선로와 패치 사이의 간격은 입력 임피던스를 조절하는 역할을 하고, 패치의 슬롯의 길이는 DMB 주파수에 해당하는 $TM_{21}$ 모드의 공진 주파수를 조절하는 역할을 한다. 제안된 안테나를 제작 및 측정을 하였다. 제작된 안테나는 GPS와 DMB 주파수에서 만족할만한 대역폭을 가지고 공진을 일으키며, GPS 대역에서는 broadside 방사 패턴을 가지고 DCS 대역에서는 코니컬 빔 방사 패턴을 가진다.

• 한국항공우주학회지
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• 제35권2호
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• pp.157-164
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• 2007

발사체 접속링은 위성체와 발사체간의 접속부로서 위성체에서 발생하는 모든 구조적 하중을 발사체로 전달시켜주는 역할을 하며, 가장 극심한 하중을 받는 부위 중의 하나이다. 특히, 통신해양기상위성은 비대칭적인 하중의 대형 연료탱크로 인해 발사체 접속링에 연료탱크 지지대라는 구조물이 필요하다. 본 논문에서는 통신해양기상위성의 초기설계단계에서 연료탱크 지지대의 적합한 형상을 결정하기 위한 연구를 수행하였다. 이를 위해 발사하중과 설계제한조건을 분석하고, 최적화 알고리즘과 구조물 단순화 기법을 사용하였다. 제안한 3가지 형상 중 Model 3이 하중감소에 있어 강점이 있었으나, 최종적으로 Model 1이 무게중심 조절 및 제작의 용이성 등을 고려할 때 통신해양기상위성을 위해 가장 적합하게 적용될 수 있을 것이다.

• Bulletin of the Korean Chemical Society
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• 제30권2호
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• pp.459-463
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• 2009

Furoxanaldehydes possessing phenyl or alkenyl groups at the 3- or 4-position of the furoxan ring were designed for alkyne formation on a solid surface. Furoxans 2 and 3 were prepared from the corresponding alkenes 2a and 3a by the reaction with NaN$O_2$ in acetic acid. Furoxan 4, in which the furoxan ring is conjugated with a double bond, was prepared from bis(bromomethyl)benzene 4a in 5 steps using the Wittig reaction of aldehyde 1 as the key step. The electron beam-mediated fragmentation of furoxanaldehydes 1-4 in a mass spectrometer was exploited by focusing on alkyne formation on the solid surface. The fragmentation of furoxan 3 possessing diaryl groups afforded diarylacetylene at high efficiency, suggesting that the aryl group conjugated with the furoxan ring could facilitate alkyne formation with the evolution of NO.

• 한국자기학회지
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• 제2권2호
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• pp.163-168
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• 1992

포항 방사광 가속기 저장링용 시제품 2극전자석의 특성측정 및 보정결과에 대하여 기술 하였다. 전자석의 저장특성 측정을 위해 Hall probe mapping 기법과 rotating coil 기법과 rotating coil 기법을 동시에 사용하였다. 자장측정 결과로부터 2극전자석의 요구조건을 만족하도록 자극의 양 쪽 끝 부분을 수정하였다. 보정이 끝난 전자석은 2.0 GeV의 beam energy로 동작시킬 경우(1.058 Tesla) 약 99.7%의 효율을 얻었으며, 4극 이상의 다극 오차성분도 허용오차 범위 미만으로 포항 방사광 가속 기 저장링용 2극 전자석으로 적합함이 판명 되었다.

• Journal of the Optical Society of Korea
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• 제16권1호
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• pp.80-84
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• 2012

A high reflectance mirror, which has very low absorption and scattering loss, was coated onto a crystalline substrate by ion beam sputtering and then annealed at $450^{\circ}C$. We carefully selected the mirror coating material, and designed the high reflectance mirror, in order to avoid UV degradation which comes from the He-Ne plasma. We measured the surface roughness of the Zerodur substrate using phase shift interferometry and atomic force microscopy, and compared it with the TIS scattering of the mirror. The cavity ring-down method was used to measure the absorption of the mirror, and the thin film structure was correlated to its results. We also compared the optical properties of coated mirrors before and after annealing.

• 소성∙가공
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• 제1권1호
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• pp.33-41
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• 1992

Sintered P/M connecting rod is forged to increase density and to satisfy dimensional specifications. Flow of the materials is different form that of wrought materials due to pores in the preform. The Mises yield function was modified to. include the first invariant of stress tensor, and the associated flow rule was derived by applying the normality rule to the yield function. Axisymmetric and plane-strain finite element analyes were carried out for the ring and beam portions of the connecting rod, respectively. The flow of the preform and density change of the analysis are presented in this paper. A load-stroke curve was also presented by superimposing analysis results for the ring and beam portions.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2012년도 제42회 동계 정기 학술대회 초록집
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• pp.229-229
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• 2012

It is significant issue to control the unwanted transverse electric (TE) modes in the vacuum chamber for preventing the position reading noise from the beam position monitor (BPM) of storage ring. We introduce shunt structure to control the frequency distribution of TE resonance modes excited in the vacuum chambers of the Pohang Light Source II (PLS-II). The design of shunt structure is performed using the full three dimensional finite-difference time-domain (FDTD) simulation. It is verified that the sympton of the BPM noise is not oberved up to the beam current of 190 mA in the commmissioning of PLS-II.

• 열처리공학회지
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• 제10권3호
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• pp.165-171
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• 1997

Laser hardening for the piston ring groove of ductile cast iron was tried. Mechanical and microstructural investigation for the hardened area indicated that the laser heating technique could replace conventional induction hardening process completely and further showed that post grinding process would be eliminated by minimizing bulging of heat treated area. In laser hardening, the volume increase caused by martensitic phase transformation proved to be less than $10{\mu}m$, which insures no post machining on the hardened surface. As expected, the depth of hardening was inversely proportional to the beam scanning velocity and the highest surface hardness was obtained at the beam velocity of 0.75m/min. Heat treatment using phosphate coating demonstrated quite comparable result to the case of graphite suscepter.