• Journal of Welding and Joining
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• 제13권2호
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• pp.122-131
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• 1995

The effects of cooling rate on the microstructures, precipitation of Cu-cluster, .epsilon.-Cu and impact toughness of high strength low alloy(HSLA) steel were studied using hardness tester, impact tester, DSC(differential scanning calorimetry), AES(auger electron spectroscopy) and TEM(transmission electron microscopy). Not only the Cu-precipitates but also the segregation of Cu, As, Sb, P, S, N, Sn along grain boundary were not observed at the specimens heat treated from 800.deg. C to 300.deg. C with the cooling time of 12-125 sec. The Cu-cluster, .epsilon.-Cu are formed by introducing ageing after cooling and the effect of precipitates on hardening increase after cooling was the same in all cooling rate. The peak hardness was obtained at an ageing of 500.deg. C in all cooling conditions. The impact energy become higher as the cooling time increases. This fact can be explained to be due to the tempering effect applied on the cooling stage since the present alloy has a relatively high Ms temperature and the local high concentration of the retained austenite.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2008년도 하계학술발표대회 논문집
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• pp.925-930
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• 2008

As office automation appliances and communication equipments are adopted in office buildings, internal heat gains increase gradually. When making simulation model, internal heat gains are usually set up with standard values or ignored. Therefore, the impact of the internal heat gains has been ignored or not been focused although it is recognised as significant contributor to heating/cooling load of buildings. This study focused on the impact of internal heat gains on curtain wall buildings. the amount and schedules of heat internal gains profiles not only affect the profiles of heating/cooling loads, but also make impact on reducing the effectiveness of high performance glazing systems. It is important to identify internal heat gains profiles before considering the installation of high performance glazing systems.

• JSTS:Journal of Semiconductor Technology and Science
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• 제12권3호
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• pp.297-312
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• 2012

For future multi-core processors, 3D integration is regarded as one of the most promising techniques since it improves performance and reduces power consumption by decreasing global wire length. However, 3D integration causes serious thermal problems since the closer proximity of heat generating dies makes existing thermal hotspots more severe. Conventional air cooling schemes are not enough for 3D multi-core processors due to the limit of the heat dissipation capability. Without more efficient cooling methods such as liquid cooling, the performance of 3D multi-core processors should be degraded by dynamic thermal management. In this paper, we examine the architectural impact of cooling methods on the 3D multi-core processor to find potential benefits of liquid cooling. We first investigate the thermal behavior and compare the performance of two different cooling schemes. We also evaluate the leakage power consumption and lifetime reliability depending on the temperature in the 3D multi-core processor.

• Safety and Health at Work
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• 제10권2호
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• pp.219-223
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• 2019

Background: Ice cooling vests can cause tissue damage and have no flexibility. Therefore, these two undesirable properties of ice cooling vest were optimized, and the present study was aimed to compare the impact of the optimized ice cooling vest and a commercial paraffin cooling vest on physiological and perceptual strain under controlled conditions. Methods: For optimizing, hydrogel was used to increase the flexibility and a layer of the ethylene vinyl acetate foam was placed into the inside layer of packs to prevent tissue damage. Then, 15 men with an optimized ice cooling vest, with a commercial paraffin cooling vest, and without a cooling vest performed tests including exercise on a treadmill (speed of 2.8 km/hr and slope of %0) under hot ($40^{\circ}C$) and dry (40 %) condition for 60 min. The physiological strain index and skin temperature were measured every 5 and 15 minutes, respectively. The heat strain score index and perceptual strain index were also assessed every 15 minutes. Results: The mean values of the physiological and perceptual indices differed significantly between exercise with and without cooling vests (P < 0.05). However, the difference of the mean values of the indices except the value of the skin temperature during the exercises with the commercial paraffin cooling vest and the optimized ice cooling vest was not significant (P > 0.05). Conclusions: The optimized ice cooling vest was as effective as the commercial paraffin cooling vest to control the thermal strain. However, ice has a greater latent heat and less production cost.

• 대한금속재료학회지
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• 제47권9호
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• pp.523-532
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• 2009

In this study, four API X80 linepipe steel specimens were fabricated with varying cooling rates and finish cooling temperatures, and their microstructures and crystallographic orientations were analyzed to investigate the effects of cooling conditions on their tensile and Charpy impact properties. All the specimens consisted of acicular ferrite, granular bainite, and secondary phases such as martensite and martensiteaustenite constituent. The volume fraction of secondary phases increased with increasing cooling rate, and the higher finish cooling temperature resulted in the reduction in volume fraction and grain size of secondary phases. According to the crystallographic orientation analysis data, the effective grain size and unit crack path decreased as fine acicular ferrites having a large amount of high-angle grain boundaries were homogeneously formed, thereby leading to the improvement of Charpy impact properties. The specimen fabricated with the higher cooling rate and lower finish cooling temperature had the highest upper shelf energy and the lowest energy transition temperature because it contained a large amount of fine secondary phases homogeneously distributed inside fine acicular ferrites, while its tensile properties well maintained.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2004년도 춘계학술대회 논문집
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• pp.391-394
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• 2004

The main purpose of the present study has been placed on investigating the effects of controlled cooling on the microstructures and mechanical properties of 0.2C-0.2Si-0.8Mn-B steel for cold forming. The steel was processed in steel making factory(EAF, VD) and casted to $\Box160$ billet then reheated in walking beam furnace and rolled to coil, rolling stock was acceleratly cooled before coiling. Microstructual observation, tensile test and charpy impact tests were conducted. The mechanical properties and microsture of the steel were changed by cooling condition. The grain size of rolled product decreased with increasing cooling rate, resulting in increase of impact toughness and tensile strength, elongation and reduction of area . From the result of this study, it is conformed that mechanical properties and microstructure of 0.2C-0.2Si-0.8Mn-B steel for cold forming were enhanced by accelerated cooling.

• 환경영향평가
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• 제32권3호
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• pp.176-186
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• 2023

도시열섬(Urban Heat Island; UHI)은 도시가 인근 지역에 비해 뜨거운 현상을 의미하며 도시 내부의 건물의 구성, 토지피복의 종류 등이 변화하기 때문에 발생한다. 도시열섬을 완화하기 위한 방법으로 녹지공간의 조성인데, 녹지가 제공하는 냉각효과의 경우 녹지의 내부 구성 요소 및 녹지의 크기에 따라 변화한다. 본 연구는 다양한 토지피복으로 구성된 수원시를 대상으로 녹지의 크기와 녹지를 구성하는 요소들에 따른 냉각효과의 차이를 확인하고, 녹지의 인근 토지피복에 따라 녹지로부터 제공되는 냉각효과의 차이를 고찰하고자 한다. 연구 결과, 녹지의 초기 온도는 산림의 비율이 높을수록, 그리고 호수가 존재할수록 낮아졌다. 냉각효과 중 하나인 냉각강도는 숲의 비율이 높을수록 강해졌지만, 초기 온도가 더 큰 영향을 미쳤다. 다만 냉각 거리는 녹지의 크기나 구성에 따라 달라지지 않음을 확인했다. 본 연구의 결과는 도시의 계획 시 열섬을 완화하기 위한 녹지 설계 방안을 제시한 다는 점에 의의를 가진다.

• 비파괴검사학회지
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• 제12권2호
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• pp.21-29
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• 1992

Acceleration signal characteristics of a steel plate, impacted by steel balls, were studied in an attempt to apply the experimental results to the impact location and mass estimation of metallic loose parts in the cooling system of nuclear power plants. Experimental results show that the variation of maximum acceleration amplitude and impact contact time due to the change of ball mass and impact velocity can be well explained by the Hertz impact theory. The frequency spectral pattern shifted slightly in spite of the increase of impact velocity and impact location. Ball mass, however, strongly affected the frequency spectral pattern. Hence the frequency spectrum can be used for estimation of the mass of unknown loose parts in the cooling system.

• 설비공학논문집
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• 제23권11호
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• pp.747-753
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• 2011

The purpose of this study was to quantify the impact of the ventilation rate on heating and cooling energy consumption in a detached house. For it, a series of simulations for the application of the diverse ventilation rate (ACH) were computationally conducted for a prototypical detached residential building in the cold climate (Detroit, Michigan) and hot/humid climate (Miami, Florida) of USA. Analysis revealed that ventilation is a significant heat losing source in the cold climate; thus, the higher ventilation rate significantly increases the heating energy consumption and energy cost in the cold climate; while the impact on energy increase for heating and cooling energy consumption is similar in hot/humid climate with less significancy compared to cold climate. The research outcome of this study could be a fundamental data for determining the optimal ventilation rate in terms of indoor air quality, but also building energy performance well.

• 한국유체기계학회 논문집
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• 제15권4호
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• pp.33-41
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• 2012

In the present work, a parametric study on double-jet film-cooling has been carried out to enhance the film-cooling effectiveness using three-dimensional Reynolds-averaged Navier-Stokes analysis. The shear stress transport turbulence model is used as the turbulence closure. The lateral ejection angles and the lateral and streamwise distance between the centers of the cooling holes are chosen as the geometric parameters. The spatially averaged film-cooling effectiveness averaged over an area of 8 hole diameters in width and 30 hole diameters in streamwise length is used to evaluate the performance of film-cooling. The parameter of the lateral distance has the largest impact on the film cooling effectiveness compared to the others. On the other hand, the parameter of streamwise distance gives the least influence on the film cooling effectiveness.