• Title/Summary/Keyword: bottom temperature

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Effect of Foam Volume ratio and Curing Temperature on Compressive Strength of Lightweight using Bottom Ash Aggregates (바텀애시 경량골재 콘크리트 압축강도에 대한 기포 혼입률 및 양생온도의 영향)

  • Lee, Kwang-Il;Yang, Keun-Hyeok
    • Proceedings of the Korean Institute of Building Construction Conference
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    • 2019.05a
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    • pp.168-169
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    • 2019
  • This study examined the effect of foam volume ratio and curing temperature the air dry density and compressive strength of lightweight concrete using bottom ash. Test results showed that the lightweight concrete possessed the compressive strength of 3.4~22.7 MPa at the air dry density of 1,041~1,583 kg/m3.

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Construction and Evaluation of Thermal Crack Stability about Bottom Slab of the #219 LNG Underground Tank in Incheon (인천 LNG 지하탱크 #219 Bottom Slab시공 및 온도균열 안정성 평가)

  • Son, Young-Jun;Ha, Jae-Dam;Um, Tai-Sun;Lee, Jong-Ryul;Park, Jong-Sik
    • Proceedings of the Korea Concrete Institute Conference
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    • 2006.11a
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    • pp.689-692
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    • 2006
  • The crack of concrete induced by the heat of hydration is a serious problem, particularly in massive concrete structures. In order to control the temperature crack of massive concrete, the selection of appropriate materials like low heat cement, mixture materials, etc. is essential. In tills study, mix proportion using low heat portland cement and lime stone powder was designed and the best mix proportion, B-1, was selected. When bottom slab of the #219 LNG tank in Incheon was constructed, concrete temperature was measured. And thermal stress was analyzed about bottom slab of the LNG tank. As results of the thermal analysis, crack index was 1.60 in bottom slab and satisfied with construction specifications(over 1.0).

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FE Analysis on the Design Safety of Inner Tank Bottom Plate in Terms of Cryogenic Temperature Loadings (초저온 하중을 고려한 내부탱크 바닥판의 설계 안정성에 관한 유한요소해석)

  • Kim Chung Kyun;Cho Seung Hyun
    • Journal of the Korean Institute of Gas
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    • v.8 no.3 s.24
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    • pp.8-15
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    • 2004
  • This paper presents von Mises stress, deformation, and rotating distortion moment characteristics of inner tank bottom plate as a function of a cryogenic temperature difference along the radial distance from the center area to the corner one. The calculated results show that the filling level of LNG at the beginning of the cool-down process is very important for the design safety analysis of the inner tank. Obviously the thermal loading by a temperature difference between the LNG vapor gas of $-80^{\circ}C$ and a LNG temperature of $-162^{\circ}C$ affects to the thermal related characteristics of the bottom plates and annular one. From the computed results, the temperature difference by a vapor gas and liquid of LNG may lead to the thermal instability of the bottom plate. This phenomenon may cause the system failure of an inner tank.

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Isothermal Characteristics of a Rectangular Parallelepiped Sodium Heat Pipe

  • Boo Joon Hong;Park Soo Yong
    • Journal of Mechanical Science and Technology
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    • v.19 no.4
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    • pp.1044-1051
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    • 2005
  • The isothermal characteristics of a rectangular parallelepiped sodium heat pipe were inves­tigated for high-temperature applications. The heat pipes was made of stainless steel of which the dimension was $140\;m\;(L)\;{\times}\;95m\;(W)\;{\times}\;46 m\;(H)$ and the thickness of the container was 5 mm. Both inner surfaces of evaporator and condenser were covered with screen meshes to help spread the liquid state working fluid. To provide additional path for the working fluid, a lattice structure covered with screen mesh wick was inserted in the heat pipe. The bottom surface of the heat pipe was heated by an electric heater and the top surface was cooled by circulating coolant. The concern in this study was to enhance the temperature uniformity at the bottom surface of the heat pipe while an uneven heat source up to 900 W was in contact. The temperature distribution over the bottom surface was monitored at more than twenty six locations. It was found that the operating performance of the sodium heat pipe was critically affected by the inner wall temperature of the condenser region where the working fluid may be changed to a solid phase unless the temperature was higher than its melting point. The maximum temperature difference across the bottom surface was observed to be $114^{\circ}C$ for 850 W thermal load and $100^{\circ}C$ coolant inlet temperature. The effects of fill charge ratio, coolant inlet temperature and operating temperature on thermal performance of heat pipe were analyzed and discussed.

Structure and Electrical Properties of SiGe HBTs Designed with Bottom Collector and Single Metal Contact (Bottom Collector와 단일 금속층 구조로 설계된 SiGe HBT의 전기적 특성)

  • Choi, A.R.;Choi, S.S.;Yun, S.N.;Kim, S.H.;Seo, H.K.;Shim, K.H.
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2007.06a
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    • pp.187-187
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    • 2007
  • This paper presents the electrical properties of SiGe HBTs designed with bottom collector and single metal layer structure for RF power amplifier. Base layer was formed with graded-SiGe/Si structures and the collector place to the bottom of the device. Bottom collector and single metal layer structures could significantly simplify the fabrication process. We studied about the influence of SiGe base thickness, number of emitter fingers and temperature dependence (< $200^{\circ}C$) on electrical properties. The feasible application in 1~2GHz frequency from measured data $BV_{CEO}$ ~10V, $f_r$~14 GHz, ${\beta\simeq}110$, NF~1 dB using packaged SiGe HBTs. We will discuss the temperature dependent current flow through the e-b, b-c junctions to understand stability and performance of the device.

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Physical Envirionment Associated with Upwelling off the Southeast Coast of Korea (한국 남동해안의 용승과 관련된 물리환경)

  • Lee, Jae Chul;Kim, Dae Hyun
    • Korean Journal of Fisheries and Aquatic Sciences
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    • v.51 no.5
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    • pp.579-589
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    • 2018
  • Data from the two bottom moorings of ADCP (acoustic doppler current profiler), coastal weather station and CTC (conductivity temperature depth) observations for 2001 were analyzed to describe the physical processes associated with upwelling off the southeast coast of Korea. Winds were favorable for upwelling during summer, but were not correlated with currents. Shoaling of isotherms toward the coast due to the baroclinic tilting of the strong East Korean Warm Current (EKWC) provided a favorable background for immediate upwelling-response of surface temperature to southerly winds. This baroclinic effect was supported by a significant inverse coherence between the upper-layer current and bottom temperature near the coast. This upwelling is similar to the Guinea Current upwelling, which is driven by remote forcing (Houghton, 1989). Persistent southward flow was observed below approximately $10^{\circ}C$ isotherm throughout the observation period.

Simulation of Water Temperature in the Downstream According to Withdrawal Types of Dam using EFDC Model (댐 방류형태가 하류 하천 수온변화에 미치는 영향 예측)

  • Park, Jae-Chung;Yoon, Jin-Hyuk;Jung, Yong-Moon;Son, Ji-Yeon;Song, Young-Il
    • Journal of Environmental Impact Assessment
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    • v.21 no.5
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    • pp.715-724
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    • 2012
  • In this study, we simulated water temperature in the downstream according to withdrawal types of dam using EFDC model. Three scenarios were assumed as water was released from the surface layer, the middle layer, and the bottom layer at intervals of 10m depth. In case of the surface layer withdrawal, the water temperature rose from March and lowered gradually after it reached a peak in August. The middle and the bottom layers effluence temperatures were lower than the surface layer temperature by maximum $15.9^{\circ}C$(in July), but after September, temperature inversion appeared. It was advantageous for the surface layer withdrawal to decrease cold damage and fog in downstream area and was possible to the middle and the bottom layers withdrawal from August to September. However, the reliability of model should be improved by accumulating the real-time information of water temperature.

Microclimate, Growth and Yield in Wheat under North-South and East-West Row Orientation (이랑방향에 따른 밀 군락의 미기상과 생육 및 수량)

  • Yoon, Seong-Tak;Jerry, Johnson
    • KOREAN JOURNAL OF CROP SCIENCE
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    • v.49 no.3
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    • pp.155-159
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    • 2004
  • This experiment was carried out to evaluate the microclimate of wheat canopy, growth and yield characteristics of wheat under north-south and east-west row orientation. The variety used in this experiment was "AG South 2000", which was developed in USA. Solar radiation, air temperature, relative humidity, and soil temperature were monitored by data logger from March to May in 2002, The ratio of light penetration to the bottom from the upper canopy was 36.8% in north-south and 21.4% in east-west row orientation. Temporal march of light penetration to the bottom from March to May decreased as wheat developed canopy structure and decreased a little from May as plant were matured. The highest light penetration to the bottom from upper canopy occurred at 13:00 in both north-south and east-west row orientations, respectively which were 36 times in north-south and 27 times in east-west row orientation, respectively. Daily maximum temperature at the bottom of canopy occurred at 14:00 with 29 times in north-south, while 19 times were obtained at 14:00 and 15:00, respectively in east-west row orientation. Relative humidity at the bottom of the canopy in east-west yow orientation showed higher than that of north-south row orientation. Occurrence of daily maximum soil temperature of north-south showed one hour later compared with east-west yow orientation. 1000 grain weight and test weight of north-south row orientation was higher than those of east-west vow orientation. Correlation coefficient between solar radiation of upper canopy and 1000 grain weight showed r=$0.8132^{*}$, and between air temperature of upper canopy and number of spikes per $\textrm{m}^{2}$ and 1000 grain weight showed significant positive correlation with r=$0.8139^{*}$, and r=$0.8293^{*}$, respectively.

The Characteristics of Seasonal Variations of Water Quality in Mokpo Harbour 1. Physical Environment and Organic Pollution (목포항 수질의 계절적 변화 특성 I. 물리 환경과 유기 오염)

  • 김광수
    • Journal of the Korean Society of Marine Environment & Safety
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    • v.5 no.2
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    • pp.57-65
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    • 1999
  • The in situ observations and the seawater analyses were conducted at all seasons from July 1996 to April 1999 for the purpose of describing the characteristics of seasonal variations of water quality in Mokpo harbour, Korea. Vertical stratification started to be formed in water column in spring, developed in summer and disappeared in fall. In summer, vertical density distribution of water column was found to be in stable structure with lower temperature and higher salinity of bottom water, and the vertical mixing of water between surface and bottom layers was restricted. In winter, however, surface water was found to be similar to bottom water in temperature and salinity, and water column was in unstable structure and in well-mixed condition between surface and bottom waters. The saturation percentage of dissolved oxygen(DO) in bottom water of inner part of Mokpo harbour at all seasons was shown to be decreased to the third grade or under the third grade of Korean standards of seawater quality. In particular, dissolved oxygen was oversaturated in surface water and undersaturated in bottom water in summer, due to stratification and organic pollution. The difference of DO concentration between surface and bottom waters was found to be greater in spring and summer than in fall and winter, due to stratification and photosynthesis of phytoplankton. The concentrations of chemical oxygen demand(COD) over the entire waters of Mokpo harbour were found to fluctuate from below the third grade to the first grade of Korean standards through all seasons and COD concentrations of same seasons were shown to be different year after year. In particular, in view of COD, the annual average seawater quality of Mokpo harbour was evaluated to be in third grade of Korean standards, due to organic pollution. The average COD of surface water was greater than that of bottom water in spring and summer, due to the autochthonous COD caused by production of phytoplankton in surface waters, while the average COD of surface water was similar to that of bottom water in fall and winter, due to the vertical mixing of water between surface and bottom layers.

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Lumped System Analysis on the Lunar Surface Temperature Using the Bottom Conductive Heat Flux Model (달 표면온도 예측을 위한 집중계 해석방법과 하부 열유속 모델의 적용)

  • Kim, Taig Young
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.47 no.1
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    • pp.66-74
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    • 2019
  • Instead of securing thermophysical properties throughout the entire lunar surface, a theoretical method to predict the lunar surface temperature accurately using improved Lumped System Model (LSM) was developed. Based on the recently published research, thermal mass per unit area at the top regolith layer is assumed uniform. The function of bottom conductive heat flux was introduced under the theoretical background. The LSM temperature prediction agrees well with the DLRE measurement except for dusk, dawn and high latitude region where the solar irradiation is weak. The relative large temperature discrepancy in such region is caused by the limit of the bottom conductive heat flux model. The surface temperature map of the moon generated by the LSM method is similar to the DLRE measurement except for the anomalous temperature zones where surface topography and thermophysical properties appear in highly uneven.