• 한국생명과학회:학술대회논문집
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• 한국생명과학회 2007년도 제48회 학술심포지움 및 추계국제학술대회
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• pp.104.2-104.2
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• 2007

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• 대한기계학회논문집
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• 제19권5호
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• pp.1300-1307
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• 1995

The effect of thermal stratification on the turbulent dispersion from a fine cylindrical heat source was experimentally examined in a wind tunnel with and without a strong temperature gradient. A 0.5 mm dia. nichrome wire was used as a line heat source. Turbulent intensities, r.m.s. value of temperature and convective heat fluxes were measured by using a hot-wire and cold-wire combination probe. The results show that the peack value and the spread of the vertical turbulent intensity for the stratified case are far lower than those in the neutral case, which indicates that the stable temperature gradient suppresses the vertical velocity component. All of the third order moments including heat fluxes measured in the stable condition have very small values than those of the neutral case. This nature suggests that the decrease of scalar fluctuations in the stably stratified flow is mainly due to the suppression ofthe turbulent diffusion processes by the stable stratification. A simple gradient model with a composite timescale which has a simple weighted algebraic mean between dynamic and thermal time scale yields reasonably good numerical values in comparison with the experimental data.

• 열처리공학회지
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• 제34권2호
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• pp.53-59
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• 2021

Due to high specific strength and low density, AZ series magnesium alloys have been receiving high interest as a lightweight material. However, their industrial application is limited due to the phenomenon that the strength decreases at elevated temperature by the occurrence of softening effect because of the Mg17Al12 phase decomposition. To solve this problem, many research were conducted to increase the high-temperature strength by forming a thermal stable second-phase component by adding new elements to the AZ magnesium. Especially, adding Ca to AZ magnesium has been reported that Ca forms the new second-phase. However, studies about the analysis of decomposition or precipitation temperature, formation composition, and components to understand the formation behavior of these precipitated phases are still insufficient. Therefore, the effect of Ca addition to AZ61 on the phase change and microstructure of the alloy during annealing was investigated. As a result of analysis of the initial and heat-treated specimen, AZ61 formed α-Mg matrix and precipitated phase of Mg17Al12, and AZX611 formed one more type of precipitated phase, Al2Ca. Also, Al2Ca was thermal stable at high temperatures. And after annealing, the laves phase was decomposed to under 10 ㎛ size and distributed in matrix.

• 태양에너지
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• 제12권2호
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• pp.9-17
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• 1992

This is an experimental work concerning about an application of a heat pipe to an evacuated-glass-tube solar collector system. A methanol heat pipe with length of 0.7 m and diameter of 8 mm was manufactured and tested to compare its performance with that of freon thermosyphon which was originally used in a solar collector system fabricated at Thermomax Co.. Then this methanol heat pipe was utilized to be one component, i.e. heat transfer element, of the present experimental model of a solar collector. This model was performed the operation test as its absorber plate was irradiated by infrared lamps. The following results were obtained. (1) The methanol heat pipe was showed a stable operation when the variation of axial heat transport was $0{\sim}40$ watts and that of inclination angle was $30{\sim}90^{\circ}$. (2) The heat transport capability of the heat pipe was proved to be higher than that of the thermosyphon, because the heat transport limitation of the latter was occured at about 30 watt. (3) The heat pipe in a solar collector was also showed good performance as it transmitted absorbed energy.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2004년도 춘계학술대회 논문집
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• pp.400-403
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• 2004

A non-heat기leafed steel does not need quenching and tempering processes that are called a heat treatment differently from conventional steel. Since the tensile strength of this steel is higher than 900MPa, a conventional forming process should be changed to incremental forming process such as a cross wedge rolling that requires lower load capacity than conventional ones. In this paper, the cold cross wedge rolling (CWR) die has been designed using CAD/CAE In order to produce near-net-shaped component of ball stud of non-heat-treated cold steel. Finite element analyses were applied in order to investigate process parameters of CWR. Results provide that the stretching angle and the forming angie at knifing zone in CWR process is important parameter to be the stable process under the low friction coefficient condition.

• 한국환경보건학회지
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• 제16권2호
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• pp.89-95
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• 1990

This study was investigated to the energy recovery by the pyrolysis of waste tyre. the pyrolysis of the waste tyre was made by using the pyrolysis chamber for the gasification and the combustion chamber for the combustion of the pyrolysis gas. In batch system, the amount of waste tyre was put 150kg in the pyrolysis chamber and the proper air flow rate for the stable production of the pyrolysis gas was 0.95Nm$^{3}$ /min. the production time of the pyrolysis gas was stable above 210minutes, and the stable production rate was above 3.8Nm$^{3}$ /min. The production temperature of pyrolysis gas was 170$^{\circ}$C and combustion temperature of pyrolysis gas was 1,000$^{\circ}$C. The combustible component of washing gas in pyrolysis gas of waste tyre was CO, CH$_{4}$, $C_{2}H_{6}$ and $C_{3}H_{8}$, and total amount was 22.7%. Heat value of condensed material was 9,804Kcal/kg. The average concentration of air pollutants between cyclone and scrubber was CO 420.4ppm, SO$_{x}$ 349.8ppm. NO$_{x}$ 68.Sppm, HCl 24.4ppm and Dust 240.0g / Nm$^{3}$, respectively.

• Proceedings of the National Institute of Ecology of the Republic of Korea
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• 제1권1호
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• pp.68-73
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• 2020

Korean fir (Abies koreana) is an evergreen coniferous tree species that is unique to South Korea. A. koreana is found in a limited sub-alpine habitat and is considered particularly vulnerable to climate change. Identification of populations vulnerable to climate change is an important component of conservation programs. In this study, a heat stress-induced transcriptome RNA-seq dataset was used to identify a subset of six genes for assessment as candidate marker genes for ecologically vulnerable populations. Samples of A. koreana were isolated from ecologically stable and vulnerable regions of the Halla and Jiri mountains, and the expression levels of the six candidate markers were assessed using quantitative real-time polymerase chain reaction. All six of the candidate genes exhibited higher expression levels in samples from vulnerable regions compared with stable regions. These results confirm that the six high temperature-induced genes can be used as diagnostic markers for the identification of populations of A. koreana that are experiencing stress due to the effects of climate change.

• Nuclear Engineering and Technology
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• 제56권4호
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• pp.1135-1144
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• 2024

With the increasing ratio of renewables in the grid, a low-carbon and stable base load source that also is capable of load tracking is in demand. Sodium cooled fast reactors (SFRs) coupled to thermal heat storage system (THS) is a strong candidate for the need. This research focuses on the designing and performance validation of a two-tank THS based on molten salt to integrate with a 280 MW_th sodium cooled fast reactor. Designing of the THS includes the vital component, sodium-to-salt heat exchanger which is a technology gap that needs to be filled, and designing and parameter selection of the tanks and related pumps. Modeling of the designed THS is conducted followed by the description of operation strategies and control logics of the THS. Finally, the dynamic simulation of the designed THS is conducted based on Fortran. Results show, the proposed power system meets the need of the design requirements to store heat for 18 h during a day and provide 500 MW_th for peak demand for the rest of the day.

• 한국초지조사료학회지
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• 제25권3호
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• pp.169-176
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• 2005

본 연구에서는 국내에서 반추가축용 조사료 원으로 많이 사용하고 있는 화본과 수입조사료 6종(bermuda grass hay, klein grass hay, oat hay, orchard grass straw, tall fescue straw and timothy hay)에 대하여 최근 NRC의 nutrient requirements of daily cattle(7th revised edition, 2001)에서 권장하는 사료의 영양성분 분석방법에 따라 일반조성분과 함께 heat-stable $\alpha-amylase$ treated neutral detergent fiber (aNDF), acid detergent fiber (ADF), acid detergent lignin(ADL), neutral detergent insoluble crude protein(NDICP)과 acid detergent insoluble crude protein(ADICP) 등의 함량을 분석하고 영양성분간의 Pearson의 상관계수를 산출하였다. 조사료에 따라 다소 차이는 있으나 oat hay는 CP와 NDICP(p<0.05), CP와 ADICP(p<0.01)의 상관관계가 높게 나타났고, orchard grass straw는 CP와 NDICP의 상관관계가 높게 나타났다(p<0.05). Tall fescue straw도 CP와 NDICP의 상관관계가 높게 나타났으며(p<0.01), timothy hay는 CP와 ADICP의 상관관계가 높게 나타났다(p<0.05). Klein grass hay는 CF와 aNDF (p<0.01), oat hay는 CF와 ADF(p<0.05), orchard grass straw는 CF와 ADL(p<0.05), tall fescue straw는 CF와 aNDF(p<0.01), CF와 ADF(p<0.01), timothy hay는 CF와 aNDF(p<0.01), CF와ADF(p<0.05), CF와 ADL(p<0.01)에서 높은 상관관계를 나타내었다. 이렇게 영양성분 간에 상관관계가 높은 성분들 간에는 앞으로 조사료의 영양성분에 영향을 미치는 제 요인들을 고정하여 상관관계를 조사하고, 분석점수를 많이 하여 회귀식을 만들 수 있다면 수입조사료 평가에 실질적인 적용이 가능할 것으로 생각된다.

• Applied Microscopy
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• 제30권2호
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• pp.185-191
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• 2000

초고온 archaeon인 Thermococcus profundus에서 매우 거대한 단백질 복합체를 분리 및 구조를 규명하였다. 거대 복합체는 93kDa단백질(P93 complex)로 구성된 homomultimer이며, 강한 내열성을 보여주고 있다. 순수 분리한 P93 complex를 SDS(최종 농도 1%)와 $85^{\circ}C$에서 12시간 항온시킨 후, SDS-PAGE와 전자현미경에서 구조적 변화를 관찰할 수 없었다. 음착색된 P93 complex의 전자현미경 사진에서 하나의 형태만을 보여주고 있으며, 구조의 규명을 위해 image processing을 하였다. 이의 구조는 3대칭 중심에 core(혹은 hole)이 뚜렷이 존재하며 이를 중심으로 단백질이 모여 있는 형태를 보여 주고 있다. 또한 P93 complex는 가장자리에서 뚜렷한 형태를 보여주지 않은 부분, 즉 flexible부분을 포함하고 있다. Gel filtration과 2차원 구조를 기초로 P93 complex는 24 homomultimer로 되어 있음을 추정하였다.