• 설비공학논문집
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• 제22권11호
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• pp.773-780
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• 2010

The dispersion of plume which is emitted from a chimney is governed by a lot of factors： wind, local terrain, turbulence intensity of atmosphere, and temperature, etc. In this study, we numerically investigate the plume dispersions for various altitudinal temperature gradients and wind speeds. The normal atmosphere has the temperature decrease of $0.6^{\circ}C/100m$, however, actually the real atmosphere has the various altitudinal temperature profiles according to the meteorological factors. A previous study focused on this atmospheric temperature gradient which induces a large scale vertical flow motion in the atmosphere thus makes a peculiar plume dispersion characteristics. In this paper, the effects of the atmospheric temperature gradient as well as the wind speed are investigated concurrently. The results for the developing processes in the atmosphere and the affluent's concentrations at the ambient and ground level are compared under the various altitudinal temperature gradients and wind speeds.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2004년도 추계학술대회논문집
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• pp.226-229
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• 2004

The temperature difference between die and workpiece has been frequently caused to various surface defects. The distribution and change for the temperature of forged part should be analyzed to prevent the generation of various defects related with the temperature. The surface temperature changes were mainly affected by the interface heat transfer coefficient. Therefore, the coefficient is necessary to predict the temperature changes of die and workpiece. The temperature calculated by FEM result might be well compared with the measured temperature. However, it is impossible to measure directly the temperature distribution of forged part. Therefore, the comparisons between measured temperature and predicted values are preformed by the microstructure in various temperature. Since the differences of microstructure could be obvious, the temperature criteria is set near by the incipient melting temperature. The predicted temperatures are well coincided with the measured values.

• 소성∙가공
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• 제10권2호
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• pp.101-110
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• 2001

The thermal problem of press work is classified into two cases. First, the temperature of forming die passively rises due to the heating effect of plastic deformation. The warm forming is the second case in which the external heating is applied to the die and blank holder. So, the purpose of this study is to provide database for the forming characteristics at various temperature conditions. In this study, the tensile test was carried out for the commercial steel sheets such as SCPI and SCP3C with the thickness of 0.7mm and 1.4mm respectively. The tensile strength, total elongation, Lankford value and the flow curve have been obtained at the temperature of $25^{\circ}C$, $50^{\circ}C$, $100^{\circ}C$, $150^{\circ}C$, $200^{\circ}C$, $250^{\circ}C$ and $300^{\circ}C$, respectively. From the results, we can see that both the tensile strength and total elongation decrease as the temperature increases. In the light of anisotropy, the effect of thickness is dominant than the material specs. For the temperature dependency of flow curves, there are only small differences for the work-hardening exponent, and the strength intensity decreases monotonically as temperature increases. The present results we useful as input data for the analysis of sheet metal forming processes with the various temperature conditions.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1996년도 춘계학술대회 논문집
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• pp.215-219
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• 1996

We developed a part of hydraulic stroke sensing cylinder for te purpose of position controlbyusing magnetic sensor and evaluated variously its performance its performance. In this paper, for the evaluation of the developed cylinder under various temperature change, thermal control systems are designed and controlled. It is composed of an heater case, temperature sensor, and interface circuits which included SCR(silicon controlled rectifier) for the control of the voltage's phase. To obtain various temperature conditions, the thermal systems are controlled by using Ziegler-Nichols PED tuning method. The thermalcontrol systems are used to experiment to evaluate whether the developed cylinder can obtain a stable output signal for detecting a stroke of the cylinder under the controlled temperature condition.

• 한국안전학회지
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• 제5권1호
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• pp.7-18
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• 1990

This study measured the smouldering temperature of dust layer for various combustible natural polymer material by practical apparatus. The dust layer was either put on the preheated plate of constant temperature, or formed with cylinderical metal sleeve of various diameters and depths at room temperature and then heated up to a pre-determined smouldering temperature. Plots of arrival times versus smouldering temperature were made to compare the smouldering characteristics with kinds of dusts. The natural polymer material was divided into theree groups by characteristics of smouldering mechanism. This groups are cellulose group, lipide group and glucose group.

• Elastomers and Composites
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• 제43권4호
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• pp.213-220
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• 2008

본 연구에서는 다양한 온도에서 고무재료의 경도에 대한 가교시스템의 영향에 대해 고찰하였다. 다양한 가교밀도의 시편을 얻기 위하여, NR과 SBR에 여러 가지 함량의 황 또는 peroxide를 첨가하여 가교하였다. 가교된 고무시편의 온도변화에 따른 경도변화와 가교밀도 변화를 측정하고 상호관계를 고찰하였으며, 시편에 발생하는 온도응력을 측정하여 온도변화에 따른 엔트로피의 변화를 조사하였다. 실온 이상에서 NR과 SBR 시편은 온도가 증가함에 따라 경도가 증가하였으며, 측정된 온도응력도 온도가 증가함에 따라 증가하였다. 그러나 측정조건 내에서 시편의 가교밀도 변화는 온도의 변화에 의해 거의 영향이 없었고 가교시스템에도 무관하였다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 춘계학술대회
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• pp.1243-1249
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• 2004

This study is focused on the comparison between the internal saturation temperature of the working fluid and the surface temperature of adiabatic zone of two-phase closed thermosyphons with various helical grooves. Distilled water, methanol and ethanol have been used as the working fluid. In the present work, a copper tube of the length of 1200mm and 14.28mm of inside diameter is used as the container of the thermosyphon. Each of the evaporator and the condenser section has a length of 550mm, while the remaining part of the thermosyphon tube is adiabatic section. A experimental study was carried out for analyzing the performances of having 50, 60, 70, 80, 90 helical grooves. A plain thermosyphon having the same inner and outer diameter as the grooved thermosyphons is also tested for the comparison. The results show that the numbers of grooves and the type of working fluids are very important factors for the operation of thermosyphons. A good agreement between the internal saturation temperature of working fluid and the surface temperature of adiabatic zone of two-phase closed thermosyphons with various helical grooves is obtained.

• 마이크로전자및패키징학회지
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• 제22권4호
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• pp.1-5
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• 2015

In high temperature aircraft electronics, aluminium based brazing filler is the prime choice today. Aluminium and its alloys have compatible properties like weight minimization, thermal conductivity, heat dissipation, high temperature precipitation hardening etc. suitable for the aerospace industry. However, the selection of brazing filler for high temperature electronics requires high temperature joint strength properties which is crucial for the aerospace. Thus the selection of proper brazing alloy material, the composition and brazing method play an important role in deciding the final reliability of aircraft electronic components. The composition of these aluminium alloys dependent on the addition of the various elements in the aluminium matrix. The complex shapes of aluminium structures like enclosures, heat dissipaters, chassis for electronic circuitry, in avionics are designed from numerous individual components and joined thereafter. In various aircraft applications, the poor strength caused by the casting and shrinkage defects is undesirable. In this report the effect of various additional elements on Al based alloys and brazing fillers have been discussed.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2016년도 제50회 동계 정기학술대회 초록집
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• pp.289.1-289.1
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• 2016

Germanium (Ge) with higher carrier mobility and a lower crystallization temperature has been considered as the channel material of thin-film transistors for display applications. Various methods were studied for crystallizaion of poly-Ge from amorphous Ge at low temperature. Especially Metal induced crystalliazation (MIC) process was widely studied because low process cost. In this paper, we investigate copper diffusion process of different thick (70 nm, 350 nm) poly-Ge film obtained by MIC process at various temperatures (250, 300, and $350^{\circ}C$) through atomic force microscopy (AFM), Raman spectroscopy, and secondary ion mass spectroscopy (SIMS) measurement. Crystallization completeness and grain size was similar in all the conditions. Copper diffusion profile of 370 nm poly-Ge film show simirly results regardless of process temperature. However, copper diffusion profile of 70 nm poly-Ge film show different results by process temperature.

• 한국태양에너지학회 논문집
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• 제27권4호
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• pp.67-75
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• 2007

This study intends to the adequacy inspection of the room temperature variation rate that is available in the building heat performance evaluation index, so we performed the sensitivity analysis about the room temperature variation rate and the energy consumption in the room. For these purpose, we supposed the models which are composed of the various window area, insulation thickness and ventilation rate. Then we analyzed the simulation using the ESP-r and Seoul weather data. In this research, the pattern of the increasing & decreasing rate of annual load according to the change of the various design factors is similar to the pattern of increasing & decreasing rate of not the K-values but the room temperature variation rate. Also we derive the optimum value of the various design factors and the room temperature variation rate in this analysis model. Further study is to be required the development of convenient tool to use in the real design.