• 한국자동차공학회논문집
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• 제7권7호
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• pp.122-128
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• 1999

CARS(Coherent anti-Stokes Raman Spectroscopy) temperature measurement under engine-like condition was validated by measuring unburned gas temperatures of premixed propane-air flame in a constant volume combustion chamber. The measured temperatures were compared with predictions of 2 zone flame propagation model. End-gas temperatures were measured were measured by CARS technique in a conventional 4 cylinder DOHC spark-ignition engine fueled with PRF 80. Cylinder pressure was measured simultaneously with CARS signal and used as a parameter on fitting CARS spectrum to library of theoretical spectra. There was a good agreement between the measured temperature and adiabatic core temperature calculated from measured cylinder pressure. Significant heating by pre-flame reaction in the gas was observed in the late part of compression stroke.

• 대한기계학회논문집
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• 제18권11호
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• pp.2913-2921
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• 1994

In SMA(shape memory alloy), the degradation by fatigue is one of the most important problems to be overcome, when SMA is used for robot-actuator material. The actuator is operated repeatitively for long time and its repeating operation develops the fatigue degradation of SMA. The fatigue degradation changes the transformation temperature and deformation behavior and results in inaccurate operation control of robot. Accordingly, the changing behavior of transformation temperature and deformation which results from repeating operation is to be investigated in advance and the scheme to resolve those problems have to be made for the design of actuator. In this study, the fatigue tests were carried out on SMA specimens prepared to have different condition of aging time and pre-strain with the direct-current heating-cooling method, which was a general method of operation in robot actuators. The behavior of transformation temperature and deformation were examined and analyzed in each specimen and the study was performed to establish the optimistic manufacturing condition of SMA against the fatigue degradation.

• 한국분말재료학회지
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• 제11권4호
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• pp.294-300
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• 2004

This study for preparation of aluminum nitride (AlN) with high purity was carried out by self-propagating high-temperature synthesis method in two different systems, $Al-N_{2}$ and $Al-N_{2}$-AlN, with the change of nitrogen gas pressure and dilution factor. On the occasion of $Al-N_{2}$ system, unreacted aluminum was detected in the product in spite of high nitrogen pressure, 10 MPa, This may be caused by obstructing nitrogen gas flow to inner part of molten and agglomerate of aluminum, formed in pre-heating zone. In $Al-N_{2}$-AlN system, AlN with a purity of 95% or ever can be prepared in the condition of $f_{Dil}\geq0.5$, $P_{N_{2}}\geq$ 1 MPa, and the purity can be elevated to 98% over in the condition of $f_{Dil}$ = 0.7 and $P_{N_{2}}$ = 10 MPa.

• 한국화재소방학회논문지
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• 제15권2호
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• pp.1-5
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• 2001

전분 분말의 온도에 따른 열적 안정성을 조사하기 위하여 시차주사열량계(DSC, Differential Scanning Calorimeter) 빛 열중량 분석기(TGA, Thermogravimetric Analysis)를 이용하여 온도에 따른 발열개시 온도, 발열량 등을 조사하였으며, 자연발화 시험기를 이용하여 시료량에 따른 전분 분말의 연소특성을 시간에 따른 온도의 변화를 측정하여 연소개시시간 및 연소시 상승하는 온도를 측정함과 동시에 육안으로 연소특성을 조사하고자 하였다. 한편 자연발화 시험기 내부의 공기흐름에 따른 연소특성을 조사하기 위하여 송풍과 무풍 상태에서의 연소특성을 조사하고자 하였다. 선분 분말의 열분석 결과 승온속도가 증가할 수록 발열개시온도가 저온부로 이동하고 있으며, 발열량도 크게 증가하였다. 또한, 자연발화 실험결과 전분의 양이 증가할수록 훈소 개시온도가 낮아지고, 연소형태는 모두 훈소였다. 자연발화 시험기 내부가 송풍상태일 때 보다 무풍상태로 실험하였을 경우 훈소 개시시간이 다소 빨라지고 있으며, 발열최고온도도 크게 나타났다.

• 한국자원식물학회지
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• 제25권4호
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• pp.456-464
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• 2012

본 연구는 야생 참당귀의 무균묘 확보, 대량생산체계 확립 및 품종개발을 위해 기내발아와 기관유도에 미치는 PGRs의 영향을 알아보고자 실시하였다. 종자발아 실험은 전처리로 $GA_3$ 침지시간(0, 24h, 48h, 72h) 및 종자의 처리 방법(대조구, 기계적가상 처리, 표면 메탄올 가열 소독법)을 달리하여 실시하였다. 그 결과 $GA_3$에 침지시키지 않고 메탄올 가열법으로 처리한 종자를 0.5 mg/L $GA_3$가 첨가된 배지에서 가장 높은 발아율(15%)을 보였으나 저조하여 발아율 향상을 위해 초음파(frequency 80 KHz) 및 PGRs($GA_3$, BA, TDZ)를 처리하였다. 그 결과 초음파 처리 후 메탄올 가열법으로 처리 한 종자를 0.1 mg/L $GA_3$가 첨가된 배지에 치상하여 발아율(60%)을 증진 시킬 수 있었다. 기내 발아된 식물체로부터 기관유도에 미치는 PGRs(2,4-D, NAA, TDZ, BA)의 영향을 살펴본 결과 캘러스 유도는 줄기, 뿌리, hypocotyl을 1.0 mg/L NAA + 0.5 mg/L BA 처리구에 치상하였을 때 높은 유도율을 보였다. 신초와 뿌리유도는 각각 hypocotyl(PGRs 무첨가)과 뿌리(0.1 mg/L NAA 첨가구)에서 효율적으로 분화되었다. 또한 줄기(1.0 mg/L 2,4-D 처리구)와 hypocotyl(0.1 mg/L NAA 처리구) 조직에서 체세포배가 발생되어 MS 기본배지에 계대배양하여 정상적인 식물체로의 육성이 가능하였다. 본 연구를 통해 무균묘 확보 및 대량생산 체계를 확립하였으며 이를 통해 신품종 개발에 유용할 것으로 판단된다.

• 한국세라믹학회지
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• 제49권6호
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• pp.620-624
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• 2012

The role of moisture remaining inside the deposition chamber during the formation of the cubic boron nitride (c-BN) phase in BN film was investigated. BN films were deposited by an unbalanced magnetron sputtering (UBM) method. Single-crystal (001) Si wafers were used as substrates. A hexagonal boron nitride (h-BN) target was used as a sputter target which was connected to a 13.56 MHz radiofrequency electric power source at 400 W. The substrate was biased at -60 V using a 200 kHz high-frequency power supply. The deposition pressure was 0.27 Pa with a flow of Ar 18 sccm - $N_2$ 2 sccm mixed gas. The inside of the deposition chamber was maintained at a moisture level of 65% during the initial stage. The effects of the evacuation time, duration time of heating the substrate holder at $250^{\circ}C$ as well as the plasma treatment on the inside chamber wall on the formation of c-BN were studied. The effects of heating as well as the plasma treatment very effectively eliminated the moisture adsorbed on the chamber wall. A pre-deposition condition for the stable and repeatable deposition of c-BN is suggested.

• 대한토목학회논문집
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• 제35권1호
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• pp.77-84
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• 2015

고온에 노출된 GFRP 보강근의 인장실험을 수행하였다. 본 실험을 위한 고온노출조건은 $200^{\circ}C$ 이하의 온도에 3분간 노출하는 것으로 하였다. 이러한 조건은 다른 연구자들의 시험에서 적용한 고온노출조건과 비교하여 경미한 고온노출조건이다. 고온에서와 고온노출 후 GFRP 보강근의 인장강도와 탄성계수를 비교하였다. 실험결과, 고온에서 GFRP 보강근의 인장성능이 감소하는 것으로 나타났으나, 고온노출 후 보강근의 인장성능은 거의 고온노출전의 수준으로 회복되는 것으로 나타났다. 이와 같은 결과는 화재로 손상 받은 GFRP 보강 콘크리트 구조물의 평가를 위하여 중요한 자료가 된다.

• 한국생산제조학회지
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• 제21권6호
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• pp.915-919
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• 2012

In constructing all kinds of equipment and steel structure, parts with discontinuities such as weld defects formed in the welded structure can generate fatigue cracks that results in damage or accidents. In this study, weld zones are investigated with X-rays and the latent images are put on film. Weld zone defects can be verified by developing the film. As weld defects are investigated by radiographic testing and correlated with the welding condition, more appropriate welding conditions can be found. According to the result of X-ray radiographic inspection of butt welding ATOS 80 high-strength steel with a thickness of 12mm, the best conditions for welding without creating weld defects are 4 weld-passes, a protective gas of 20% $CO_2$ and 80% Ar, a protective gas flow of 20L/min, a welding current of 200A, an arc voltage of 24V, a welding speed of 14.4cm/min, a welding rod angle of $50^{\circ}$, a welding gap of 5 mm with a ceramic base, and sand pre-heating to $160^{\circ}$ Celsius prior to welding.

• 한국레이저가공학회지
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• 제13권2호
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• pp.10-16
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• 2010

Laser-assisted machining is dependent on absorbed energy density into workpiece. Generally, the absorptivity of laser beam is dependent on wave length of laser, materials, surface roughness, etc. Various shapes and energy densities for beam irradiation can be used to laser-assisted machining. In this thesis, efficient method of heat source modeling was developed and designed by using one fundamental experimental trials. And then, laser-assisted machining of rod-shaped cast iron was simulated by using commercial FEM code MARC. Simulations and experiments with various conditions were carried out to determine suitable condition of pre-heating for laser-assisted turning process. Temperature distribution of cutting zone could be predicted by simulation.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2005년도 추계학술대회 논문집
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• pp.373-376
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• 2005

In recent years, there has been a growing need fur productivity improvement of ACS wire (Aluminum clad Steel wire) In optical communication market. So, it is necessary to improve the production speed and following quality of ACS wire to reduce the unit cost of the products. In this study, the pre-heating temperature and cladding speed is chosen as the factors can influence the mechanical and metallurgical properties during cladding, and the changing behavior of mechanical property and microstructure by controlling above two factors are investigated. And the bearing length and approach angle in cladding die are selected as the important elements for designing optimum die enabling high speed cladding. So we carried out FE(Finite Element) analysis using the above two elements as variables. This paper aims to understand the change of mechanical properties and microstructure according to the change of each factor during cladding and suggest the optimized cladding condition to get the best quality of OPGW. And also we would like to introduce the optimum die structure that enables high-speed cladding.