• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제55권11호
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• pp.514-519
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• 2006

To improve the mean-life and the reliability of power cable, we have investigated specific heat (Cp) and thermal conductivity of XLPE insulator and semiconducting materials in 154[kV] underground power transmission cable. Specimens were made of sheet form with the seven of specimens for measurement. Specific heat (Cp) and thermal conductivity were measured by DSC (Differential Scanning Calorimetry) and Nano Flash Diffusivity. Specific-heat measurement temperature ranges of XLPE insulator were from $20[^{\circ}C]\;to\;90[^{\circ}C]$, and the heating rate was $1[^{\circ}C/min]$. And the measurement temperatures of thermal conductivity were $25[^{\circ}C],\;55[^{\circ}C]\;and\;90[^{\circ}C]$. In case of semiconducting materials, the measurement temperature ranges of specific heat were from $20[^{\circ}C]\;to\;60[^{\circ}C]$, and the heating rate was $1[^{\circ}C/min]$. And the measurement temperatures of thermal conductivity were $25[^{\circ}C]\;and\;55[^{\circ}]C$. From these experimental results both specific heat and thermal conductivity were increased by heating rate because volume of materials was expanded according to rise in temperature. We could know that a small amount of CNT has a excellent thermal properties.

• 생물환경조절학회지
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• 제22권1호
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• pp.13-18
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• 2013

본 연구는 참외 개화시의 기온과 상대습도가 화분의 발아에 미치는 영향을 검토하고자 '만리장성', '오복꿀' 및 '조은대'의 3 품종을 재료로 하여 개화 시 온도를 $15^{\circ}C$, $25^{\circ}C$ 및 $35^{\circ}C$, 상대습도를 30%, 60% 및 90%의 처리를 두고 실험하였다. 기온조건에 따른 화분 발아율은 $25^{\circ}C$에서 채취한 것이 가장 높았고 $15^{\circ}C$에서 채취한 것이 가장 낮은 경향이었으며 품종별 화분 발아율은 '만리장성'이 가장 높았고 다음이 '오복꿀'이었으며 '조은대'가 가장 낮은 경향이었다. 화분관 신장길이는 기온조건별로는 $35^{\circ}C$에서 채취한 것이 가장 길었고 다음이 $25^{\circ}C$ 에서 채취한 것이었으며 $15^{\circ}C$에서 채취한 것은 현저히 짧았으며, 품종에 따라서는 '오복꿀'이 가장 길었다. 상대습도 조건에 따른 화분 발아율은 습도조건에 따라 뚜렷한 차이는 없으나 습도가 높을수록 높은 경향이었으며, 품종간에도 큰 차이가 없으나 '만리장성'과 '조은대'에 비해 '오복꿀'에서 낮았다. 그러나 화분관 신장길이는 처리간에 뚜렷한 차이를 나타내어 60%의 상대습도에서 채취한 것이 가장 길었으며, 다음이 30%의 상대습도에서 채취한 것이며 90%의 상대습도에서 채취한 것은 현저히 짧았다. 품종별 화분관 신장길이는 '오복꿀'이 가장 길었고 '조은대'가 가장 짧았다.

• 한국패류학회지
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• 제31권1호
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• pp.35-41
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• 2015

실험에 사용된 미세조류는 이매패류 종묘생산시 유생과 치패의 먹이생물로 주로 이용되고 있는 Isochrysis galbana, Pavlova lutheri, Chaetoceros simplex, Tetraselmis tetrathele 등 4종을 선정하였으며, 배양환경으로 수온 (20, 25, 30, $35^{\circ}C$), 염분 (20, 25, 30, 33 psu) 그리고 조도 (60, 100, $140{\mu}mol\;m^{-2}s^{-1}$) 를 서로 달리하여 4종의 미세조류에 대한 성장을 조사하였다. I. galbana의 성장은 수온 $20^{\circ}C$ 보다 $25^{\circ}C$에서 빠른 성장을 나타내었으며, 수온 $25^{\circ}C$일 때 일간 성장률은 염분 33 psu에서 0.413으로 가장 높았고, 20 psu에서 0.368로 가장 낮게 나타났다 (P < 0.05). 25 psu에서 일간 성장률은 0.383으로 30 psu 보다 낮게 나타났고, 20 psu 보다 높은 경향을 보였다 (P < 0.05). 이와 같은 수온과 염분에 따른 미세조류의 성장률은 종별로 다소 차이는 있으나 P. lutheri, T. tetrathele에서도 I. galbana의 성장과 유사한 경향을 나타내었다. 한편, C. simplex의 성장은 수온 $25^{\circ}C$ 보다 $30^{\circ}C$에서 빠른 성장을 나타내었으며, 수온 $30^{\circ}C$에서 일간 성장률은 배양 10일째 염분 33 psu에서 0.428로 가장 높았고, 20 psu에서 0.389로 가장 낮게 나타났다 (P < 0.05). 그리고 서로 다른 조도에서 배양한 미세조류 4종의 성장은 $100{\mu}mol\;m^{-2}s^{-1}$ 보다 $140{\mu}mol\;m^{-2}s^{-1}$의 조도에서 가장 빠른 성장을 나타내었다 (P < 0.05).

• 한국농림기상학회지
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• 제16권1호
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• pp.51-58
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• 2014

배의 휴면기간 중 저온 유지 시간 및 온도에 따른 내동성을 비교하고자 감천배, 만풍배, 신고, 원황, 추황배, 풍수, 한아름, 행수, 화산, 황금배 등의 1년생 가지를 각각 $-21^{\circ}C$, $-24^{\circ}C$, $-27^{\circ}C$, $-30^{\circ}C$, $-33^{\circ}C$의 온도로 6, 9, 12시간 동안 처리한 후 꽃눈 발아율, 전해질 누출률, TTC검정을 하였다. 저온처리 시간에 따른 꽃눈발아율은 $-21^{\circ}C$에서 6시간일 경우 품종간 거의 차이가 없었으나 온도가 낮아지고 지속시간이 길어질수록 낮아졌다. 전해질 누출률은 $-30^{\circ}C$ 이하에서는 저온지속시간에 관계없이 대부분의 품종이 30%이상의 높은 전해질 누출률을 보여 온도가 낮아질수록 저온지속 시간이 길수록 전해질 누출률이 높아졌다. 저온에서 높은 발아율을 보였던 만풍배, 신고, 추황배는 $-30^{\circ}C$ 9시간에서 각각 26.1%, 14.7%, 28.3%로 다른 품종보다 낮은 전해질 누출률을 보였다. TTC 검정을 통한 흡광률은 $-21^{\circ}C$에서 6시간일 경우 66.0~96.5%, 9시간에는 49.4~91.9%, 12시간에는 37.3~89.4%로 저온유지 시간이 길어질수록 흡광률이 낮아졌다. 배의 품종별 내동성 확인 결과 꽃눈발아율은 전해질누출률 또는 TTC 검정을 통한 흡광률과의 높은 상관관계를 보였으며 배의 외재휴면 기간 중 내동성은 저온 유지시간 및 온도에 따라 다르며 품종별 저온 피해 한계온도가 다름을 확인할 수 있었다.

• Advances in concrete construction
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• 제5권5호
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• pp.513-537
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• 2017

In this study, the fracture toughness $K_{IC}$ of high performance concrete (HPC) was investigated by conducting three-point bending tests on a total of 240 notched beams of $500mm{\times}100mm{\times}100mm$ subjected to heating temperatures up to $450^{\circ}C$ with exposure times up to 16 hours and various heating and cooling rates. For a heating rate of $3^{\circ}C/min$, $K_{IC}$ for the hot concrete sustained a monotonic decrease trend with the increasing heating temperature and exposure time, from $1.389MN/m^{1.5}$ at room temperature to $0.942MN/m^{1.5}$ at $450^{\circ}C$ for 4-hour exposure time, $0.906MN/m^{1.5}$ for 8-hour exposure time and $0.866MN/m^{1.5}$ for 16-hour exposure time. For the cold concrete, $K_{IC}$ sustained a two-stage decrease trend, dropping slowly with the heating temperature up to $150^{\circ}C$ and then rapidly down to $0.869MN/m^{1.5}$ at $450^{\circ}C$ for 4-hour exposure time, $0.812MN/m^{1.5}$ for 8-hour exposure time and $0.771MN/m^{1.5}$ for 16-hour exposure time. In general, the $K_{IC}$ values for the hot concrete up to $200^{\circ}C$ were larger than those for the cold concrete, and an inverse trend was observed thereafter. The increase in heating rate slightly decreased $K_{IC}$, and at $450^{\circ}C$ $K_{IC}$ decreased from $0.893MN/m^{1.5}$ for $1^{\circ}C/min$ to $0.839MN/m^{1.5}$ for $10^{\circ}C/min$ for the hot concrete and from $0.792MN/m^{1.5}$ for $1^{\circ}C/min$ to $0.743MN/m^{1.5}$ for $10^{\circ}C/min$ for the cold concrete after an exposure time of 16 hours. The increase in cooling rate also slightly decreased $K_{IC}$, and at $450^{\circ}C$ $K_{IC}$ decreased from $0.771MN/m^{1.5}$ for slow cooling to $0.739MN/m^{1.5}$ for fast cooling after an exposure time of 16 hours. The fracture energy-based fracture toughness $K_{IC}$' was also assessed, and similar decrease trends with the heating temperature and exposure time existed for both hot and cold concretes. The relationships of two fracture toughness parameters with the weight loss and the modulus of rapture were also evaluated.

• Journal of Welding and Joining
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• 제34권2호
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• pp.46-53
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• 2016

Effect of heating rate on microstructure of brazed joints with STS 304 Printed Circuit Heat Exchanger (PCHE),which was manufactured as large-scale($1170(L){\times}520(W)){\times}100(T)$, mm), have been studied to compare bonding phenomenon. The specimens using MBF 20 was bonded at $1080^{\circ}C$ for 1hr with $0.38^{\circ}C/min$ and $20^{\circ}C/min$ heating rate, respectively. In case of a heating rate of $20^{\circ}C/min$, overflow of filler metal was observed at the edge of a brazed joints showing the height of filler metal was decreased from $100{\mu}m$ to $68{\mu}m$. At the center of the joints, CrB and high Ni contents of ${\gamma}$-Ni was existed. For the joints brazed at a heating rate of $0.38^{\circ}C/min$, the height of filler was decreased from $100{\mu}m$ to $86{\mu}m$ showing the overflow of filler was not appeared. At the center of the joints, only ${\gamma}$-Ni was detected gradating the Ni contents from center. This phenomenon was driven from a diffusion amount of Boron in filler metal. With a fast heating rate $20^{\circ}C/min$, diffusion amount of B was so small that liquid state of filler metal and base metal were reacted. But, for a slow heating rate $0.38^{\circ}C/min$, solid state of filler metal due to low diffusion amount of B reacted with base metal as a solid diffusion bonding.

• Environmental Engineering Research
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• 제20권4호
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• pp.347-355
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• 2015

The growth kinetics of phototrophic microorganisms can be controlled by the light irradiance, the concentration of an inorganic nutrient, or both. A multi-component kinetic model is proposed and tested in novel batch experiments that allow the kinetic parameters for each factor to be estimated independently. For the cyanobacterium Synechocystis sp. PCC6803, the estimated parameters are maximum specific growth rate $({\mu}_{max})=2.8/d$, half-maximum-rate light irradiance $(K_L)=11W/m^2$, half-inhibition-rate light irradiance $(K_{L,I})=39W/m^2$, and half-maximum-rate concentration for inorganic carbon $(K_{S,Ci})=0.5mgC/L$, half-maximum-rate concentration for inorganic nitrogen $(K_{S,Ni})=1.4mgN/L$, and half-maximum-rate concentration for inorganic phosphorus $(K_{S,Pi})=0.06mgP/L$. Compared to other phototrophs having ${\mu}max$ estimates, PCC6803 is a fast-growing r-strategist relying on reaction rate. Its half-maximum-rate and half-inhibition rate values identify the ranges of light irradiance and nutrient concentrations that PCC6803 needs to achieve a high specific growth rate to be a sustainable bioenergy source. To gain the advantages of its high maximum specific growth rate, PCC6803 needs to have moderate light illumination ($7-62W/m^2$ for ${\mu}_{syn}{\geq}1/d$) and relatively high nutrient concentrations: $N_i{\geq}2.3 mgN/L$, $P_i{\geq}0.1mgP/L$, and $C_i{\geq}1.0mgC/L$.

• 한국주조공학회지
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• 제8권3호
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• pp.271-281
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• 1988

Al-bronze has a good mechanical property, corrosion resistance and castability, so being highlighted for the new copper alloy. So, effects of alloy composition and cooling rate in the mechaincal properties and solidification behavior have been investigated. The results obtained are as follows; 1) Change in volume on solidification is larger in metal mold casting than in sand mold casting. And it decreases by the addition of Al. 2) The mechanical property in metal mold casting is superior to the one in sand mold casting, and the inclination is obvious up to 9% Al, after heat-treatment ($885^{\circ}C$, $1.5hrs\;{\rightarrow}\;W\;{\cdot}\;Q\;{\rightarrow}\;540^{\circ}C$, 3hrs) 3) By adding Al, the mechanical property is slightly increased up to 9% Al, Above 9% Al, it is increased rapidly, and is accelerated by adding Fe. 4) Cooling rate and hardness, and grain size and cooling rate are related as follows in the range of $1100^{\circ}C$ to $1200^{\circ}C$ pouring temperature. Grain size(${\mu}m$)=$929.6422{\times}cooling\;rate(^{\circ}C\;/\;sec)^{-0.51537}$ Hardness(BHN)=$765.45713{\times}grain\;size({\mu}m)^{-0.31058}$.

• 한국세라믹학회지
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• 제45권5호
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• pp.280-284
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• 2008

In order to investigate residence time effect on the growth of ZrC film, the ZrC films grew with various system total pressure (P) and total flow rate (Q) by low pressure chemical vapor deposition because residence time is function of system total pressure and total flow rate. Thermodynamic calculations predict that the decomposition of source gases ($ZrCl_4$ and $CH_4$) would be low as increasing the residence time. Thermodynamic calculations results were proved by investigating deposition rate with various residence time. Deposition rate decreased with residence time of source gas increased. Besides, depletion effect accelerated diminution of deposition rate at high residence time. On the other hands, the deposition rated was increased as decreasing the residence time because fast moving of intermediate gas species decrease the depletion effect. The crystal structure was not changed with residence time. However, the largest size of faceted grain showed up to specific residence time and the size of grain was decreased whether residence time increase or not.

• 열처리공학회지
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• 제13권5호
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• pp.303-308
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• 2000

The ring gears of automobile parts are manufactured generally process chart of which is as follows : forging ${\rightarrow}$ annealing or normalizing ${\rightarrow}$ rough machining ${\rightarrow}$ hardening(Quenching-Tempering or carburizing process) ${\rightarrow}$ finish machining. Isothermal annealing process after forging is most effective in the side of improvment of machinability. On this study we selected two kinds of steel;SCM415, SCM435 of most universal and investigated microstructures to find out most suitable condition of heat treatment in proportion continuous cooling and isothermal annealing. As the cooling rate is $5^{\circ}C$ per minute in continuous cooling process, martensite and bainite are coexisted with ferrite and pearlite in SCM435 steel. If the cooling rate is slower than $5^{\circ}C$ per minute, microstructure were only ferrite and pearlite but formation of band structure can't be avoid. On the other hand, microstructure is only ferrite and pearlite regardless of cooling rate because carbon content of SCM415 steel is low. Moreover formation of band structure isn't exposed by faster cooling rate. Most optimal temperature of the isothermal annealing is from $650^{\circ}C$ to $680^{\circ}C$ in SCM435 steel. When holding time is 60 minute with $650^{\circ}C$, the identical ferrite and pearlite microstructures can be obtained.