• Journal of the Society of Cosmetic Scientists of Korea
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• v.37 no.1
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• pp.43-53
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• 2011

The conditions in fluid-bed processor for nanoencapsulation of azelaic acid-milk nano powder for acne nanocosmetics were optimized by response surface methodology (RSM). The maximum value of yield was 70.97 %. The yield was appreciably influenced by inlet air temperature, atomizing pressure, and feeding speed. The particle size increased with an increase in the feeding speed and a decrease in the atomizing pressure. The elution rate in saline solutions was appreciably influenced by inlet air temperature and atomizing pressure. The moisture content increased with higher atomizing pressure, which was demonstrated to be similar to the nanoencapsulation characteristics related to water activity. The Hunter's L and b values increased with an increase in the inlet air temperature. The optimum conditions estimated by RSM for the maximized values of yield, moisture content, particle size and elution rate in skin suitability were $67{\sim}73^{\circ}C$ of inlet air temperature, 0.6 ~ 0.8 mL/min feeding speed and 1.8 ~ 2.0 kg/$cm^2$ of atomizing pressure, respectively. These estimated values were in agreement with those measured by real experiments.

• Journal of Bio-Environment Control
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• v.32 no.4
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• pp.396-404
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• 2023

The blockage rate for three kinds of nets commonly used in agricultural facilities was assessed by using the image acquisition and its relevant processing. By using both empirical relations presented by Idel'chik and Richards and Robinson, and the blockage rate obtained from the image processing, the pressure drop through the nets was predicted and also compared with wind tunnel experiment results. The results of the study showed that the blockage rate of the net was discriminated according to such factors as the magnitude of nets, the existence of inside threads, the thickness and number of threads. In addition, the blockage rate for the incident angle of 0° when the wind blew at the front had the range of 0.22-0.29 (0.22-0.32 when considering whole incident angles from 0° to 45° by 15°). For the nets with the blockage rate of about 30% or below, the prediction by the empirical relations of by Idel'chik and Richards and Robinson showed a little higher pressure drop overall than that of the wind tunnel test, but the use of the empirical relations and the blockage rate could be thought of as providing effectively meaningful guidelines for the safe design of agricultural facilities including nets because the wind tunnel test has been tedious and expensive. Further research and potential application on the prediction technique of the pressure drop, regarding both a subtle deformation by the wind and manufacturing methods with regard to the level of knots and the existence of inside threads, needs to be done for the nets with higher blockage rate.

• Journal of the Korean Society of Propulsion Engineers
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• v.16 no.3
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• pp.49-56
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• 2012

Rupture disks are a kind of safety device in high pressure equipment and they are used to control rupture pressure in the solid rocket motor. In this paper, a series of rupture experiments was performed using rupture disks made of AISI 316L and rupture pressure of rupture disks was calculated through various assumptions in relation between elasto-plastic material properties and true stress-strain curve. Experiment and FEA indicated rupture pressure is determined by size of rupture disks. As a result of elasto-plastic analysis, only multi-linear stress-strain curve was able to calculate meaningful estimations. Experimental results also showed rupture location are decided by the size of rupture disks. Experimental and FEA results will be applied to control rupture pressure of disks.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.280-280
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• 2011

유도결합 플라즈마를 이용한 식각 장치에서 플라즈마 균일도 향상에 대한 수많은 연구가 이뤄지고 있다. 안테나의 디자인, 인가 전력과 주파수, 안테나와 기판간의 거리, 기판과 챔버 외벽간의 거리 등 다양한 변수들이 변화되어 왔다. 또한, 최근에는 식각 균일도뿐만 아니라 식각 속도 향상에도 많은 관심이 모아지면서 유동에 영향을 주는 GDP 구조가 다시 중요해지고 있다. 본 연구에서는 300 mm 식각장치를 형상화하고, GDP의 구조와 유량비에 따라 플라즈마의 균일도에 어떻게 영향을 끼지는지 사용 유체역학 전산모사 프로그램인 CFD-ACE+를 이용하여 예측해 보았다. 안테나는 2중 직렬방식으로 안쪽과 바깥쪽의 안테나에 각기 다른 전력을 인가 할 수 있는 구조를 사용했으며, 압력은 10에서 60 mTorr까지 변화시켰다. GDP의 구조는 안쪽 입구와 바깥쪽 입구가 있으며 역시 따로 유량을 조절할 수 있도록 설계하였다. 안쪽 입구는 수직방향을 향하고 있으며, 바깥쪽 입구는 90도 이내의 각을 갖도록 꺾여 있는 것과 수평방향으로 주입할 수 있는 구조, 두 가지를 사용하였다. 유량 비율은 안쪽 입구와 바깥쪽 입구를 2:8, 5:5, 8:2로 고정하였다. 우선 GDP의 구조가 90이내의 각을 갖도록 주입되는 구조에서는 어떤 유량비율에서도 약간의 vortex가 발생했다. 수직방향의 유량이 감소될수록 기판에서 멀리서 발생했으며 강도 또한 감소했다. 기판 표면에서의 압력분포 균일도도 8:2에서 2.8%, 2:8에서 0.6%로 향상되었다. 2:8의 유량 비율에서 압력을 10에서 60 mTorr까지 향상시키면 vortex 효과는 감소되나 기판에서의 압력 균일도가 0.8%까지 약간 나빠졌다. 여기서 발생되는 vortex는 GDP 구조를 수평방향으로 주입되기 함으로서 해결할 수 있었으며, 압력 균일도도 0.2%까지 향상시킬 수 있었다. 또한, 강한 수직방향의 유량은 중심에 발생하는 플라즈마의 중앙을 밀어내는 효과를 확인했으며, 실험적 증명이 추후 연구단계로 진행될 예정이다. 식각 균일도나 식각 속도를 예측하려면 CF계열의 복잡한 가스를 사용해야하기 때문에 유량이 플라즈마에 미치는 영향을 보기 위해서 본 연구에서는 단일종인 Ar 가스만을 사용하였다. 첫 단계로 이와 같이 최적화시킨 유동조건에서 복잡한 식각가스를 이용한 플라즈마 계산은 다음 단계로 준비 중에 있다.

• Journal of the Korean Institute of Gas
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• v.12 no.2
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• pp.85-91
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• 2008

The deviation of measured pressures in pipeline networks from normal or reference pressures is useful information for judging the operation of the pipeline networks. A cost-effective monitoring of pipeline networks including a leak detection capability can be realized when transient pressure variation is accurately predicted using measured conditions at supply- and demand-sides of the networks. In this study, a pipeline network analysis program was developed based on one-dimensional flow equations for compressible fluids. The validity of the present analysis was demonstrated by simulating the flow in a straight pipeline and comparing the results with the previously reported ones. Pressure and flow rate transients in several simple city-gas pipeline networks were also analyzed to show the usefulness of the developed program.

• Journal of the KSME
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• v.32 no.4
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• pp.340-350
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• 1992

이 글에서는 재료의 경년열화의 종류, 판정 방법 등에 관한 일반사항을 기술하고 고온 . 고압용 기의 경년열화현상의 대표적인 예인 T.E의 기구와 T.E감수성에 미치는 화학성분의 영향에 대해 설명하였다. 아울러 필자가 그 동안 연구해온 T.E에 의한 재료강도저하를 설명하고 수명예측을 행할 수 있는 방법을 설명하였다. 끝으로 열화의 비파괴 판정만으로 수명예측이 어려우므로 시 간에 따른 열화 정도를 파악 할 수 있는 재료강도의 주곡선을 만들어야 할 것이다. 이와 같은 실험을 하기 위해 열화재의 가속제작방법과 열화치료대책 등에 대해 설명하였다. 앞으로 국내 에서는 열화에 대한 재료강도의 주곡선이 많이 얻어져서 기계 구조물의 수명예측이 정확하게 이루어질 날이 올 것을 기대한다.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.50 no.10
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• pp.701-708
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• 2022

Since the propellant tank structure of the projectile is mainly subjected to a compressive force, there is a high risk of damage due to buckling. Large and lightweight structures such as propellant tank have a complex manufacturing process. So it requires a non-destructive test method to predict buckling load to use the structure after testing. Many studies have been conducted on Vibration Correlation Technique(VCT), which predicts buckling load using the relationship between compressive load and natural frequency, but it requires a large compressive load to predict the buckling load accurately, and it tends to decrease prediction accuracy with increasing internal pressure in structure. In this paper, we analyzed the causes of the decrease in prediction accuracy when internal pressure increases and proposed a method increasing prediction accuracy under the low compressive load for being usable after testing, through VCT combined testing and FEA result. The prediction value by the proposed method was very consistent with the measured actual buckling load.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.1
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• pp.61-69
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• 2020

This study examined the braking characteristics of a heavy haul freight train with P4a distribution valves applied to domestic high-speed freight trains. A freight train was composed of 50 cars, which is twice the normal operation. A braking test was performed to confirm the characteristics of the braking of a heavy haul. The brake cylinder pressures were measured for emergency and service braking on the 1st, 10th, 20th, 30th, and 50th cars. Because the brake signal is transmitted to the pressure through the braking tube connected to the end of the train, the rear vehicle is braking later than the vehicle ahead. Therefore, it is necessary to predict the brake pressures in all cars in a train to supplement the results of the limited tests and calculate the braking distance. The pressure in each car was determined using empirical models of linear interpolation, stepwise, and exponential models, which provided reliable information. The predictive results of the empirical models were compared with the measured results, and the exponential model was predicted relatively accurately. These results are expected to contribute to the safe operation of heavy haul freight trains and can be used to predict the braking distance and calculate the level of impact between vehicles during braking.

• Journal of the Korean Institute of Gas
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• v.26 no.6
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• pp.9-15
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• 2022

In order to verify the durability of the high-pressure hydrogen tank in the operating pressure range, a hydraulic rupture test should be performed. However, if the bubbles generated by the initial injection process of water are attached to the inner wall of the tank and remain, a sudden pressure change of the bubbles during the rupture of the pressurized tank may cause shock and noise. Therefore, in this study, the flow velocity required to remove the bubbles remaining on the inner wall of the tank was predicted through simplified formulas, and the shape of the injection nozzle to maintain the flow velocity was determined based on the shape of the hydrogen tank for the hydrogen bus. In addition, a numerical model was developed to predict the change in flow velocity according to the inlet pressure, and an experiment was performed through a model tank to prove the validity of the prediction result. As a result of the experiment, the flow velocity near the tank wall was similar to the predicted value of the analysis model, and when the inlet pressure was 1.5 to 5.5 bar, the minimum size of the removable bubble was predicted to be about 2.2 to 4.6 mm.

• Proceedings of the Korea Water Resources Association Conference
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• 2009.05a
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• pp.1186-1190
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• 2009

강수량이 예년에 비해 적은 양상은 여름강수량에 대한 부족으로 기인한다. 우리나라의 경우 장마기간의 강수와 태풍으로 인해 발생하는 강수가 전체 강수량에 많은 부분을 차지하고 있기 때문에 여름강수량이 적게 나타나게 되면 가을 가뭄 및 봄 가뭄에 대한 발생 압력도 그 만큼 커지게 되는 것이 일반적이다. 기존 연구들이 단순히 강수량을 가정하거나 시나리오를 기반으로 가뭄을 전망하는데 그치고 있으나 본 연구에서는 2009년 가뭄전망을 위해서 전지구기후모형(GCMs)의 3개월 기상예측 결과를 활용하고자 한다. 즉, APEC 기후예측 센터로부터 제공 받은 3개월 GCM Multi-Model Ensemble 예측 결과를 바탕으로 가뭄상태를 평가하였다. 따라서 본 연구의 목적은 Large-scale의 기후예측 시스템과 기상관측지점의 강수 및 온도를 연결시켜 가뭄을 전망할 수 있는 시스템을 구축하는데 있다. GCM 예측 결과를 바탕으로 2009년도 매월 강수량 및 평균 온도를 추정하여 PDSI 가뭄지수 산정에 이용하였다.