• 한국기계가공학회지
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• 제14권5호
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• pp.81-87
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• 2015

In this paper, the finite element method was used for the flow and strength analysis of aluminum alloy under friction stir welding. The simulations were carried out using Sysweld s/w, and the modeling of the sheet was executed using Unigraphics NX6 s/w. The welding variables for the analysis were the shoulder diameter, rotating speed, and welding speed of the tool. Additionally, a three-way factorial design method was applied to confirm the effect of the welding variables on the flow and strength analysis with variance analysis. From these results, the rotating speed had the greatest influence on the maximum temperature, and the maximum temperature was $578.84{\pm}12.72$ at a confidence interval of 99%. The greater the rotating speed and shoulder diameter, the greater the difference between maximum and minimum temperature. Furthermore, the shoulder diameter had the largest influence on von Mises stress, and the von Mises stress was $184.54{\pm}12.62$ at a confidence interval of 99%. In addition to the increased shoulder diameter, welding speed, and rotating speed of the tool increased the von Mises stress.

• 대한기계학회논문집
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• 제16권10호
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• pp.1955-1962
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• 1992

본 연구에서는 무한 원형관 안의 복사에 참여하는 참여가스에 면을 도입시키 면, 참여가스로부터 원형관 벽면으로의 복사 열유속(radiatve heat flux)이 증진 또는 감소되는 현상을 연구하는 데 있다. 참여가스는 흡수, 방사 특성이 온도와 파장에 변하지 않는 회체가스(gray gas)이거나, 화석 연료 연소시 연소가스의 성분이며, 복사 에 참여하는, 수증기와 이산화탄소의 혼합물이다. 편의상, 이 가스를 실제가스(real gas)라 부르기로 한다.도입면은 동축 무한 원형관(coaxial Infinite cylinder)이다. 참여가스의 성분, 계의 직경, 동축 무한 원형관 사이의 직경비, 면의 방사율, 면과 가 스의 온도가 열전달 증진에 미치는 영향을 연구하고자 한다.

• 한국주조공학회지
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• 제13권6호
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• pp.532-539
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• 1993

The effect of casting variables for making pure Al and Al-5wt%Si alloy rods free from any surface and inside defects was studied by adopting the horizontal continuous casting method with heated mold. The rods were cast under the casting conditions such as the mold temperature of $670{\sim}690^{\circ}C$, water flow rate of $0.2{\sim}0.6{\ell}/min$, and rod diameter of $4{\sim}8mm$, when the melt temperature and mold to cooler distance was fixed at $700^{\circ}C$ and 20mm, respectively. The results represented that the casting speed for good quality rod increased as the water flow rate increased, whereas, the casting speed decreased as the rod diameter or mold temperature increased. The statistical analysis of $2^3$ factorial design was also applied and the results represented that the averaged optimum casting speed for pure Al(302mm/min) was higher than that of Al-5wt%Si alloy(273mm/min) resulting from the difference of superheat applied. The effect of rod diameter on the optimum casting speed was the highest for pure Al as well as Al-5wt%Si alloy. The effect of water flow rate and mold temperature on the optimum casting speed was in decreasing order.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2009년도 추계학술대회 논문집
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• pp.238-238
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• 2009

In this work, we investigated the effect of the Zn complex concentration and growth temperature on the growth of ZnO nanorod by hydrothermal method. The ZnO nanorods were performed at condition of the various Zn complex concentration and growth temperature, 0.02 ~ 0.08 M and 60 ~ 80 $^{\circ}C$, respectably. We found from the SEM results that the diameter and length of ZnO nanorods were with increasing the growth temperature and Zn complex concentration. However, the growth condition in the two parameters wasmore than sensitive compared to Zn complex concentration on increasing the growth rate. From photoluminescence(PL) analysis, the strong band-edge emission for ZnO nanorod grown at 80 $^{\circ}C$ with 0.08 M indicated the fine crystallinity. Therefore, the diameter and length of ZnO nanorods have been able to control through the control of front growth parameters. Also, these ZnO nanorods grown low temperature will be available as building block for transparence flexible device applications.

• Journal of Ginseng Research
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• 제12권1호
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• pp.40-46
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• 1988

3년생 인삼에서 5, 10 및 20% 투광율 일복간에는 경장, 경직경, 엽면적, 근장의 차이가 없었고 근직경은 10% 및 20% 일복구에서 현저히 굵었으며 20%구에서 근중이 가장 무거웠다. 6년생 인삼에서도 20% 일복구에서 가장 근직경이 굵었고 근장은 투광율에 영향을 받지 않았으며 20% 투광 일복하에서 가장 근중이 무거웠다 근중의 증가를 위한 최적 일복투광량은 3년근에서는 18.13% 그리고 6년근에서는 21.50% 추정되었다.

• 설비공학논문집
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• 제23권1호
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• pp.54-60
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• 2011

Procedures for estimation of insulation thickness for a horizontal pipe for condensation control or personnel protection has been investigated, parallel to the previous work of a vertical wall case. Parameters include pipe diameter, emissivity, thermal conductivity, and operating temperatures. The results indicated that the surface emissivity plays a very important role in the design of insulation, specially for the case of high temperature application with low Bi. The effect of surface radiation in such case could be up to 65% of the total. Required insulation thickness for the surface temperature control increases as pipe diameter increases and as surface emissivity decreases. Adequate revision of specifications or standards to include newly invented insulation materials with high emissivity has been also suggested.

• 한국연소학회지
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• 제20권2호
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• pp.46-53
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• 2015

The relationship between mass transfer and reaction within the washcoat is investigated in a monolith type micro-scale Pt-catalytic combustor. Nondimensionalized balance equation of butane is applied in a simplified washcoat geometry having the shape of slab. Both Thiele modulus and effectiveness factor are considered to compare reaction rate and diffusion rate according to the operation temperature and the diameter of alumina nano-pores. The effect of reaction becomes stronger as the temperature increases, while the effect of diffusion becomes relatively dominant as the diameter of nano-pores increases. From the analysis of butane distribution within the washcoat, design criterion for the thickness of washcoat is discussed.

• 한국환경과학회지
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• 제20권7호
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• pp.819-828
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• 2011

This research was done to clarify the cooling effect of water particles generated from a fountain. This effect is a one way to control the heat island effect of big cities. The result of this research was drawn by setting the jets of water in a certain height, and then studying the diffusion of water particles, which is affected by the size of the particles and the wind speed, and the cooling effect caused by the diffusion. 1) When a diameter of a water drop was 500 ${\mu}m$ and the wind speed was 2.0 to 6.0 m/sec, the water drop diffused 75 to 190m, and the water vapor spread over 175 to 440 m. As a result, there was more than $0.5^{\circ}C$ of cooling effect on the temperature in the atmosphere 130 to 330m around the water fountain. 2) When a diameter of a water drop was 750 ${\mu}m$ and the wind speed was 2.0 to 6.0 m/sec, the water drop diffused 65 to 150 m, and the water vapor spread over 160 to 405 m. Moreover, there was more than $0.5^{\circ}C$ of cooling effect on the temperature in the atmosphere 110 to 275 m around the water fountain. 3) After studying on the relationship between the diameter of water drop and the wind speed, and the diffusion of water particles and the range of the atmosphere that was cooled, a result could be drawn from the research that the smaller the diameter of the water vapor gets and the faster the wind speed becomes, the wider the water particles diffuse and the cooler the atmosphere around the fountain becomes. 4) This research further extrapolates that when the ordinary water(tap water, water from river and stream) is used in a fountain, the cooling effect of the air near the fountain can be approached similarly. If the seawater is used in a fountain, there is to be more to concern not only on cooling effect on the air, but also on other effects on surrounding environment generated by the salt in seawater.

• 한국자기학회지
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• 제11권2호
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• pp.78-83
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• 2001

The thermal characteristics of TMR devices by using Fast Linear Annealing method has been studied. A computer program that employs the finite differential method has been developed to simulate the temperature distribution of a diameter of 4" silicon wafer, which is subjected to radiation heat from the halogen lamp. We adopted the temperature of 350$\^{C}$, which is the highest temperature usually used in annealing for magnetic thin films. We changed moving velocity of the lamp from 0.05 mm/sec to 1 mm/sec. The moving velocity of halogen lamp has less effect on the local peak temperature of the sample only about 40$\^{C}$. Therefore, we may be able to anneal TMR devices in such short time of 1 minute and 40 seconds per one wafer, using the Fast Linear Annealing method.

• Journal of Advanced Marine Engineering and Technology
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• 제6권1호
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• pp.49-54
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• 1982

In the equipments of industrial plant and marine engine, an exact temperature measurement is indispensable. Temperature measurement errors are induced by electrical and heat errors, and the insufficient immersion length of thermowell exerts an important effect to the haet error. In this paper, the author analyses the relation between temperature errors and the rate of immersion length to outside diameter (L/D) in order to reduce the heat errors.