• Proceedings of the KSME Conference
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• 2007.05b
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• pp.2091-2096
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• 2007

This paper presents a mathematical model for predicting the frost behavior formed on heat exchanger fins, considering fin heat conduction under frosting condition. The model is composed of air-side, the frost layer, and fin region, and they are coupled to the frost layer. The frost behavior is more accurately predicted with fin heat conduction considered (Case A) than with a constant fin surface temperature assumed (Case B). The results indicate that the frost thickness and heat transfer rate for Case B are over-predicted in most regions of the fin, as compared to those for Case A. Also, for Case A, the maximum frost thickness varies little with the fin length variations, and the extension of the fin length over 30 mm contributes insignificantly to heat transfer.

• Journal of the Korean Society for Precision Engineering
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• v.25 no.3
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• pp.126-133
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• 2008

The main objective of the present study is to achieve linear temperature distribution of cooling surface of plunger. K type thermocouples are attached at the surface of plunger to measure temperature. Nozzle and insulating material are inserted in the pin hole of the plunger for this study. Cooling water flow enters at one nozzle and leaves at three nozzles. Flow through nozzle can be activated in the pin hole, temperature of hot point around hole is decreased. Meanwhile, insulating material blocks off heat transfer, temperature of cold point around hole is increased. By combination of nozzle and insulation, heat transfer of hole is controlled effectively, as result its, temperature of plunger surface shows linear temperature distribution.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.39 no.9
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• pp.893-899
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• 2015

In the design of injection molds, the temperature distribution and deformation of the mold is one of the most important parameters that affect the flow characteristics, flash generation, and surface appearance, etc. Plastic injection analyses have been carried out to predict the temperature distribution of the mold and the pressure distribution on the cavity surface. As the input loads, we transfer the temperature and pressure results to the structural analysis. We compare the structural analysis results with the thermal expansion effect using the actual flash and step size of a smartphone cover part. To reduce the flash problem, we proposed a new mold design, and verified the results by performing simulations.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.30 no.3
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• pp.1-7
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• 2002

An experimental study was conducted to investigate the effects of leading edge extension(LEX) on the surface prssure distribution over a delta wing in a subsonic wind tunnel. Freestream velocity was 40m/sec and Reynolds number per meter was 1.7x$10^6$ with total pressure of 101Pa and total temperature of 278K. LEX changed the surface pressure distribution on the wing dramatically. Comparing with the results without LEX, the peak of pressure distribution decreased on the front chordwise location but it turned to increase on the rear chordwise location with increase of the angle of attaci. The spanwise gradient of the pressure distribution also increased in the rear chordwise location. Without LEX, the peak of pressure distribution increased and decreased irregularly with increase of the angle of attack at each chordwise location, but LEX made it increased almost linearly with increase of the angle of attack at all of the chordwise locations.

• Journal of the Korean GEO-environmental Society
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• v.18 no.11
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• pp.35-40
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• 2017

The rearside of concrete lining of tunnels constructed in cold region might experience on freezing due to the low temperature. This causes damage of concrete lining resulting in adverse affect on the durability as well as integrity of tunnel structure by causing damage to the concrete lining. In order to prevent the rearside of tunnel lining from freeing, the temperature change inside the concrete lining was measured by attaching a heating element to the tunnel lining surface and generating heat for a certain period of time. A special freezing chamber was developed to conduct the experiments considering in-situ environment. The carbone nanotube (CNT) was used as a heating element in this study. The temperature distribution of the concrete lining was measured by applying the heat to the heating element. The effect of the outside temperature and heating duration were analyzed.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.35 no.10
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• pp.1161-1170
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• 2011

This paper presents a solution to the inverse problem for the service boundary conditions of thermal-flow and structure analysis in a catalyst substrate. The exhaust-gas purification efficiency of a catalyst substrate is influenced by the shape parameter, catalyst ingredients and so on and is estimated by the thermal flow uniformity. The formulations of the inverse problem of obtaining the thermal-flow parameters (inlet temperature, velocity, heat of reaction, convective heat-transfer coefficient) and the direct problem of estimating from a given outlet temperature distribution are described. An experiment was designed and the response-surface optimization technique was used to solve the proposed inverse problem. The temperature distribution of the catalyst substrate was obtained by thermal-flow analysis for the predicted thermal-flow parameters. The thermal stress and durability assessments for the catalyst substrate were performed on the basis of this temperature distribution. The efficiency and accuracy of the inverse approach have been demonstrated through the achievement of good agreement between the thermal-flow response surface model and the results of experimental vehicle tests.

• Proceedings of the Korean Vacuum Society Conference
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• 1999.07a
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• pp.209-209
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• 1999

현재 magnetron sputter는 반도체, LCD 등을 포함하는 microelectronics 산업에서 박막형성을 위한 주요 장비로 널리 쓰이고 있으며, 소자의 고집적화 및 대형화 추세에 따라 그 이용가치는 더욱 증대되고 있다. 본 연구엣는 TFT-LCD용 Color Filter 제조시 ITO박막형성을 위해 사용하는 magnetron sputter 내부의 플라즈마 분포 및 ion kinetic energy에 대한 해석을 실시하였으며, ITO target의 erosion 형상의 원인을 실험결과와 비교하였다. Magnetron sputtering은 target에 가해지는 bias 전압(DC 혹은 RF)에 의해 target과 shield 혹은 target과 substrate 사이에서 생성될 수 잇는 플라즈마를 target 및 부분에 붙어있는 영구자석을 이용하여 target 근처에 집중시키고, target 표면과 플라즈마 사이의 전위차에 의해 가속된 이온들이 target 표면과 충돌하여 이차 전자방출을 일으킴과 동시에 target 표면에서 sputtering을 일으키고, 이들 sputtered 된 중성의 atom 들이 substrate로 날아가 박막을 형성하는 원리로 작동된다. 이때 target에서 방출되는 이차전자들은 영구자석에 의한 자기장 효과에 의해 target 근처에 갇히게 되어 중성 기체분자들과 이온화반응을 통해 플라즈마를 유지하고 그 밀도를 높혀주는 역할을 담당하게 된다. 즉 낮은 압력 및 bias 전압에서도 플라즈마 밀도를 높일수 있고 sputtering 공정이 가능한 장점을 가지고 있다. Magnetron sputtering 현상에 대한 시뮬레이션은 크게 magnetron discharge와 sputtering에 대한 해석 두가지로 나누어 볼 수 있는데, sputtering 현상 자체를 수치묘사할 수 있는 정량적인 모델은 아직까지 명확하게 정립되어 있지 않다. 따라서 본 연구에서는 magnetron plasma 자체에 대한 수치해석에 주안점을 두고 아울러 bulk plasma 영역에서 target으로 입사하는 이온들의 입사에너지 및 입사각도 등을 Monte Carlo 방법으로 추적하여 sputtering 현상을 유추해보았다. Sputtering 현상을 살펴보기 위해 magnetron sputter 내 플라즈마 밀도, 전자온도, 특히 target 및 substrate를 충돌하는 이온의 입사에너지 및 입사각 분포등을 계산하는데 hybrid 방법으로 시뮬레이션을 하였다. 즉 ion과 bulk electron에 대해서는 fluid 방식으로 접근하고, 이차전자 운동과 그로 인한 반응관계 및 target으로 입사하는 이온의 에너지와 입사각 분포는 Monte-Carlo 방법으로 처리하였다. 정지기장해석의 경우 상용 S/W인 Vector Fields를 사용하였다. 이를 통해 sputter 내 플라즈마 특성, target으로 입사하는 이온에너지 및 각 분포, 이들이 target erosion 형상에 미치는 영향을 살펴보았다. 또한 이들 결과로부터 간단한 sputtering 모델을 사용하여 target으로부터 sputter된 입자들이 substrate에 부착되는 현상을 Monte-Carlo 방법으로 추적하여 성막특성도 살펴보았다.

• Journal of Astronomy and Space Sciences
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• v.15 no.1
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• pp.91-100
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• 1998

Color indexes and effective temperatures for 25 standard stars have been determined as a pilot project which show a relationship between color index and effective temperature in ultraviolet region. The effective temperature was determined by comparing energy distribution curves derived from the IUE low dispersion spectra with Kurucz atmosphere model. The UV color index was deduced by integrating fluxes in $300{\AA}$ interval of the IUE low disperion spectra. The relation between color index and effective temperature in ultraviolet is similar with that of optical region.

• Journal of Korean Society for Geospatial Information Science
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• v.19 no.2
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• pp.55-61
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• 2011

The land use has been changed artificially and caused the result of temperature increase of city compared with the outside of city or region of park and forest. The purpose of this research is to analyze the change of the urban surface temperature with land use zoning in Jinju using Landsat TM/$ETM^+$ imagery and to provide the correlation between NDVI(Normalized Difference Vegetation Index) and urban surface temperature change. The results presented that the spatial distribution of urban surface temperature was depending on the change of NDVI values on land use zoning. Considering to the average temperature by land use zoning, industrial area was the highest temperature but green area was the lowest temperature. Also as a result of comparing the correlation between surface temperature and NDVI, the green and residential area had higher correlation values than the commercial and industrial area. These results will be played a part as one of the major factors for implementing the sustainable urban planning considering the urban heat island effect problem.

• Tunnel and Underground Space
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• v.12 no.3
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• pp.142-151
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• 2002

Claesson(2001)'s analytical solution, and two numerical models with Dirichlet and Neuman interior boundary condition respectively were investigated to estimate the transient temperature distribution with distances from the Taejon underground food cold storage pilot cavern. Claesson's solution, which is based on constant temperature boundary condition at the rock wall during a temperature decline step, showed relatively good agreement with temperature measurements in the rock mass in order of average error difference, 0.89$\^{C}$ without any adjustments on laboratory thermal properties to represent the rock mass. For the numerical model with heat flux through the rock wall, a boundary condition setting technique was newly proposed to overcome the difficulty of prescribing variable convective heat tranfer coefficient and far-field air temperature inside the cavern as they may be certainly changed according to the cooling-down time. The results showed also good agreement with measurements in order of average error difference, 1.58$\^{C}$, and were compared to those of the numerical model with fixed temperature at the rock wall. Finally, the most proper procedure to precisely predict the temperature profile around a cavern was proposed as a series of analysis steps including an analytical exact solution and numerical models.