• 한국항공우주학회지
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• 제45권12호
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• pp.1007-1012
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• 2017

본 연구에서는 우주 안테나 설계용 형상기억 폴리머 시편의 전개 시험을 수행하였다. Poly(cyclooctene)을 dicumyl peroxide를 이용하여 가교시켜 PCO 형상기억 폴리머를 제조하고, 이를 이용하여 지름이 120 mm인 전개형 안테나의 축소 모델을 제작하였다. 전개 성능 시험을 위하여 원형 형태의 형상기억 폴리머 시편을 반으로 접어 임시 형상을 만든 후 두 개의 히터로 형상기억 폴리머의 유리 전이 온도보다 $15^{\circ}C$ 높은 온도로 시편을 가열하였다. 먼저 시편을 수평 설치하여 전개 실험을 수행하였다. 시편의 전개 영상을 디지털 카메라를 사용하여 촬영한 후 트래커 프로그램을 이용하여 분석하였다. 중력의 효과를 최소화하기 위하여 수직 설치하여 다시 실험을 수행하였다. 두 실험의 결과를 비교하여 형상기억 폴리머 시편의 전개 성능을 고찰하였다.

• 한국안전학회지
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• 제31권2호
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• pp.18-25
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• 2016

The incandescent lamp is an electric light fixture with a tungsten filament heated to a high temperature, by passing an electric current through it, until it glows with visible light. The hot filament is protected from oxidation with a glass bulb that is filled with inert gas. The incandescent lamp has fire risk when combustible materials are close to its glass bulb. Because its lamp has the property which converts 90~95 percents of the electric power to heat energy. 2015 national fire statistics show that fires caused by lighting fixtures were 652 cases, and incandescent lamps(44 cases) and halogen lamps(53 cases) accounted for 15 percents in those of high heating light fixtures. Since incandescent lamp fires account for about 45 percents in the high heating light fixture, we could not overlook the fire risks by the incandescent lamp. Although many studies related with those have been conducted, incandescent lamp fires are continuously occurred. This study was carried out to study the fire risk of ignition of wood due to radiant heat of incandescent lamp. Radiant heat flux of the incandescent lamp was predicted by applying point source model, and critical distance for ignition of wood was calculated by applying integral model. The results from this study could applied to fire prevention activities related to light bulb, and it could be used in fire cause investigations related to radiant heat of incandescent lamp.

• 한국결정성장학회지
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• 제12권4호
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• pp.184-189
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• 2002

초음파 분무 MOCVD법에 의한 $(Pb_{0.91}La_{0.09})(Zr_{0.65}Ti_{0.35})O_3$(PLZT) 박막의 제조와 광학적, 전기적 특성을 조사하였다. Pb의 휘발성을 고려하여 0.2M의 precursor에 Pb를 5 wt%, 10 wt%과잉 첨가하였다. ITO-coated glass 기판 위에 산소분위기에서 30분 동안 증착한 후 in-situ 상태의 RTA (rapid thermal annealing) 방식으로 열처리를 하였다. 단일 perovskite상의 결정화 온도는 $600^{\circ}C$였다. Pb를 10 wt% 과잉 첨가한 박막의 최대 광투과율은 520nm에서 약 84%로 광학적 특성이 우수하였으며, 유전상수는 약 308의 값을 가졌고, 누설전류는 Pb를 0, 5 wt% 과잉 첨가한 PLZT 박막보다 낮은 값을 가졌다.

• 한국결정성장학회지
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• 제13권6호
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• pp.272-278
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• 2003

초음파 분무에 의한 유기금속 화학증착법 (MOCVD)법으로 $Bi_4Ti_3O_{12}$(BIT)와 Bi와 Ti 대신에 La과 V을 동시에 치환시킨 ($Bi_{3.75}La_{0.75})(Ti_{2.97}V_{0.03})O_{12}$ (BLTV)박막을 ITO/glass 기판 위에 증착하였다. 산소 분위기에서 30분 동안 증착한 후, RTA 방식의 직접삽입법으로 열처리를 하였다. 박막은 페로브스카이트상 생성 온도, 미세구조, 전기적 성질에 관해서 조사하였다. XRD(X-Ray diffraction) 측정결과 BLTV 박막의 페로브스카이트상 생성 온도는 약 $600^{\circ}C$로써 BIT의 $650^{\circ}C$보다 더 낮았다. BLTV 박막의 누설전류는 인가전압 1 V에서 $1.52\times10^{-19}$ A/cm^2$로 측정되었다 또한, $650^{\circ}C$에서 증착했을 경우 잔류 분극값이 $5.6\mu$C/$cm^2$, 항전계값 96.5 kV/cm으로 명확한 강유전성을 보이고 있다.

• 대한기계학회논문집B
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• 제26권11호
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• pp.1622-1629
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• 2002

To enhance isothermal characteristics of glass-farming surface, a rectangular parallelepiped heat pipes was fabricated, tested, and analyzed. The working fluid was sodium and the wall material was stainless steel 304. The dimension of the heat pipe was 210 (L) $\times$ 140(W) $\times$ 92(H)mm. A lattice structure covered with screen mesh was inserted to promote return of working fluid. The bottom side of heat pipe was heated electrically and the top side was cooled by liquid circulation. The temperature distribution at the bottom surface was of major concern and was monitored to determine isothermal characteristics. A frozen start-up of rectangular parallelepiped liquid metal heat pipe was tested. The operating mode of the sodium heat pipe was affected by the temperature of cooling zone, input heat flux, and the operating temperature of heat pipe. The heat pipe operated in a normal fashion as long as the heat flux was over 5.78W/cm$^2$, and the inside wall temperature of condenser part was above 95$^{\circ}C$ The maximum temperature difference at the bottom surface was observed to be 32$^{\circ}C$ when the operating temperature of the heat pipe was operating normally around 50$0^{\circ}C$. The result showed that a sodium heat pipe was very effective in reducing significantly the temperature difference in the glass-forming surface.

• 한국태양에너지학회 논문집
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• 제31권6호
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• pp.1-7
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• 2011

Sound waves and acoustic energy generated by two identical TA (ThermoAcoustic) lasers were analyzed and studied. One end of the ceramic stack was heated by a thin NiCr wire wound around that end. The other end of the stack was cooled by natural convection of atmospheric air. The wavelength of the sound waves generated by a single TA laser was four times the tube length and the amplitude of the waves increased with the heating rate. SPL (SoundPressure Level) meters and microphones were employed to measure and study the sound waves at different distances from the glass tube opening and at the focusing point of the TA laser pair for different laser position arrangements. The sound waves of the two TA lasers at the focusing point were found to be almost 180 degrees out of phase when the openings of the two lasers were very close to each other and the angle between the laser axes was small. When the two TA lasers were placed far apart, the sound wave amplitudes and the phase difference between the two laser outputs varied periodically with time. The frequencies of the sound waves changed when the openings of the two TA lasers were in close vicinity and the angle between the laser axes exceeded a certain value. In this case, the glass tube opening was no longer a pressure anti-node and the wavelength of the fundamental mode was not equal to four times the tube length.

• 공업화학
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• 제4권3호
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• pp.544-548
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• 1993

Poly(phenylene sulfide sulfone)[PPSS]를 시간과 온도를 변화시키면서 열처리를 하였을 때 이들의 유리전이 온도($T_g$)를 DSC로서 조사하였다. 그 결과 PPSS의 $T_g$는 열처리온도가 $230^{\circ}C$까지는 열처리 시간이 길어질수록 증가하다가 평형에 도달하였다. 열처리 온도가 $245^{\circ}C$ 이상에서는 열처리 시간이 길어질수록 $T_g$가 증가하다가 어느 정도 시간이 되면 감소한 뒤 다시 증가하는 것으로 나타났다. 이 현상을 경화가 진행됨에 따른 chain extension반응과 oxidative crosslinking 및 thermal crosslinking으로 설명하였다.

• 열처리공학회지
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• 제8권3호
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• pp.236-243
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• 1995

Since amorphous alloys have been known to have better mechanical and chemical properties than crystalline alloys of the same composition, a great number of studies on the formation of Al-based amorphous alloys have been carried out actively. However, little has been obtained about the effect of Rare-Earth metal and Transition metal addition on amorphous phase formed by melt spinning method. This study included fabrication of amorphous alloy $Al_{85}Ce_5Ni_{10}$ by melt spinning methods and DTA, XRD, TEM analysis to determine crystalization behavoir. Annealing treatments were carried out in Ar atmosphere under isothermal and nonisothermal conditions. The diffraction pattern of non-heated ribbons showed broad form characteristic of glass metallic alloy. The crystallization of amorphous $Al_{85}Ce_5Ni_{10}$ takes place eutedtoidly by homogeneous formation of Al and MS-1, followed by precipitation of the $Al_{11}Ce_3$ and later $MS-1{\rightarrow}Al_3Ni$ transformation.

• 한국안광학회지
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• 제3권1호
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• pp.115-120
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• 1998

RF(radio-frequency) magnetron 스퍼터링 장치에 질소가스와 아르곤가스를 동시에 주입하면서 Ti 타켓을 스퍼터링하여 $TiN_x$ 박막을 유리기판위에 제작하였다. 박막제작시 RF power supply 출력을 240W로, 증착기 내부의 온도는 $200^{\circ}C$를 유지하였다. $TiN_x$ 박막은 알곤 가스를 20sccm으로 고정시킨 상태에서 질소를 3sccm부터 9sccm까지 변화시켜가며 증착시켰다. 이때 박막의 화학적 조성과 성분비를 분석하기 위하여 XPS를 사용하였다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회A
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• pp.1091-1096
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• 2007

This paper describes the development of a small lens molding system for manufacturing the small lens like lens of a cellular phone, a small digital camera and so on. In order to manufacture a small lens, firstly, the raw material for lens with spherical shape should be manufactured by processing a glass, secondly, the mold inserted the raw material for lens should be heated till its molding temperature in the electric furnace, finally, the small lens is manufactured by applying the force using pressuring control system. In this paper, the small lens molding system with the function of force control and velocity control was developed. It is composed of a electric furnace and its temperature control system, a pressuring control system, a body, and so on. The temperature characteristic test of the electric furnace, and the force and velocity characteristic test of the pressuring control system were carried out. It was confirmed that the developed system had good functions for manufacturing a small lens.