• Nuclear Engineering and Technology
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• 제49권8호
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• pp.1654-1659
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• 2017

The boundary layer of a two-dimensional forced convective flow along a persistent moving horizontal needle in an electrically conducting magnetohydrodynamic dissipative nanofluid was numerically investigated. The energy equation was constructed with Joule heating, viscous dissipation, uneven heat source/sink, and thermal radiation effects. We analyzed the boundary layer behavior of a continuously moving needle in Blasius (moving fluid) and Sakiadis (quiescent fluid) flows. We considered Cu nanoparticles embedded in methanol. The reduced system of governing Partial differential equations (PDEs) was solved by employing the Runge-Kutta-based shooting process. Computational outcomes of the rate of heat transfer and friction factors were tabulated and discussed. Velocity and temperature descriptions were examined with the assistance of graphical illustrations. Increasing the needle size did not have a significant influence on the Blasius flow. The heat transfer rate in the Sakiadis flow was high compared with that in the Blasius flow.

• 한국식품과학회지
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• 제32권3호
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• pp.500-506
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• 2000

시차주사열량계(differential scanning calorimetry, DSC)를 사용하여 분석한 결과 밀전분으로 부터 분리한 아밀로펙틴은 밀전분의 노화특성과 일치된 특성을 나타내었다. 수분함량 8%의 아밀로펙틴과 SSL을 10 : 1의 중량 비율(w/w)로 혼합하여 DSC로 1차 가열과 냉각 후 2차 가열한 결과 $55{\sim}70^{\circ}C$의 온도범위에서 용융 peak를 나타낸 반면 SSL은 $40{\sim}55^{\circ}C$의 온도범위에서 용융 peak를 나타내어 서로 다른 융점을 나타내었다. 또한 아밀로펙틴과 SSL의 혼합물은 가열과 냉각을 반복함에 따라 결정질의 아밀로펙틴 g당 용융 peak의 엔탈피값이 증가되는 결과를 보였다. 전체 수분함량 50%에서 밀전분과 밀전분으로 부터 분리한 아밀로오스와 아밀로펙틴 각각에 대해 SSL을 5 : 1의 중량비율로 혼합하여 DSC로 1차와 2차 가열한 결과 SSL의 용융 peak 이외에 SSL과 아밀로펙틴의 결합물로 판단되는 $60-70^{\circ}C$ 범위의 가역적인 용융 peak가 관찰되었다. SSL과 아밀로펙틴 결합물은 V 도형의 아밀로오스와 지방 결합물과 차이가 있는 결정질을 나타내는 X-ray diffraction angle$(2{\theta})$ 값을 나타내었다. 전체수분함량 60%에서 SSL은 밀전분의 호화 엔탈피값을 감소시켰으며 아밀로오스와 지방결합물의 용융 엔탈피값을 증가시켰다. 동일한 전체수분함량에서 밀전분과 아밀로펙틴에 대해 SSL을 20 : 1과 10 : 1의 비율로 혼합한 겔의 저장실험은 SSL을 포함한 시료가 SSL을 포함하지 않은 시료보다 노화에 대해 억제효과를 나타내었다.

• 한국화재소방학회논문지
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• 제15권2호
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• pp.1-5
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• 2001

전분 분말의 온도에 따른 열적 안정성을 조사하기 위하여 시차주사열량계(DSC, Differential Scanning Calorimeter) 빛 열중량 분석기(TGA, Thermogravimetric Analysis)를 이용하여 온도에 따른 발열개시 온도, 발열량 등을 조사하였으며, 자연발화 시험기를 이용하여 시료량에 따른 전분 분말의 연소특성을 시간에 따른 온도의 변화를 측정하여 연소개시시간 및 연소시 상승하는 온도를 측정함과 동시에 육안으로 연소특성을 조사하고자 하였다. 한편 자연발화 시험기 내부의 공기흐름에 따른 연소특성을 조사하기 위하여 송풍과 무풍 상태에서의 연소특성을 조사하고자 하였다. 선분 분말의 열분석 결과 승온속도가 증가할 수록 발열개시온도가 저온부로 이동하고 있으며, 발열량도 크게 증가하였다. 또한, 자연발화 실험결과 전분의 양이 증가할수록 훈소 개시온도가 낮아지고, 연소형태는 모두 훈소였다. 자연발화 시험기 내부가 송풍상태일 때 보다 무풍상태로 실험하였을 경우 훈소 개시시간이 다소 빨라지고 있으며, 발열최고온도도 크게 나타났다.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 1994년도 특별강연 및 춘계학술발표 개요집
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• pp.44-47
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• 1994

The ageing behavior of Cu-bearing HSLA steels was studied by using Differential scanning calorimetry(DSC), Transmission electron microscopy and hardness tester. Two heat evolution peaks were observed during DSC scans over the temperature range of 25～590$^{\circ}C$ at a heating rate of 5$^{\circ}C$/min. The peaks appeared in low (241∼319$^{\circ}C$ : HSLA-A, 224∼310$^{\circ}C$ : HSLA-B) and high temperature (514∼590$^{\circ}C$ : HSLA-A, 451∼558$^{\circ}C$ : HSLA-B) are attributed to the formation of coherent Cu-clusters and noncoherent $\varepsilon$-Cu phase, respectively. It was confirmed that as ageing proceeds, the coherent bcc Cu-clusters transform to noncoherent fcc $\varepsilon$-Cu phase. In the case of the ageing to peak hardness at 300$^{\circ}C$ and 400$^{\circ}C$, the coherent Cu-clusters contributed to the hardening. As ageing time and temperature increase over peak hardness, noncoherent $\varepsilon$-Cu are formed and hardness decreases.

• Applied Biological Chemistry
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• 제38권4호
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• pp.353-358
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• 1995

옥수수 전분(초기 수분함량 11.4%)을 $130{\sim}220^{\circ}C$에서 건열처리하여 DSC로 열분석한 결과 $190^{\circ}C$이상에서 호화엔탈피는 감소하였고 알칼리호화시 열처리온도가 상승할수록 점도가 증가하였다. $170^{\circ}C$이상에서 열처리 온도가 높아질수록 원료전분에 비하여 최고점도를 포함한 아밀로그램상의 모든 값들, 전분호화액의 전단응력과 겉보기점도, 점조도지수 및 항복응력은 감소하였다. $90^{\circ}C$에서 호화진행에 따라 모든 시료들의 겉보기 점도와 항복응력은 상당히 증가하였으며 $190^{\circ}C$시료는 특히 초기에 급증하였으나, 점조도지수는 약간 증가한 반면에, 유동거동지수값들은 큰 차이를 보이지않았다. 그러나 $220^{\circ}C$의 경우 모든 값들이 다른 시료들에 비하여 크게 낮았다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2005년도 춘계학술대회 논문집
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• pp.19-24
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• 2005

To improve mean-life and reliability of power cable, we have investigated specific heat (Cp) and thermal conductivity of XLPE insulator and semiconductive materials in 154kV underground power transmission cable. Specimens were respectively made of sheet form with EVA, EEA and EBA added 30wt%, carbon black, and the other was made of sheet form by cutting XLPE insulator in 154kV power cable. 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 semiconductive 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.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제55권1호
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• pp.6-10
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• 2006

To improve mean-life and 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 respectively made of sheet form with EVA, EEA and EBA added $30[wt\%],$ carbon black, and the other was made of sheet form by cutting XLPE insulator in 154(kV) power cable. 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 $1[^{\circ}C/mon].$ 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 $1[^{\circ}C/mon].$ And the measurement temperatures of thermal conductivity were $25[^{\circ}C],\;55[^{\circ}C].$ In addition we measured matrix of semiconducting materials to show formation and growth of carbon black in base resins through the SEM. 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.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제54권11호
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• pp.477-482
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• 2005

We have investigated volume resistivity and thermal properties showed by changing the content of carbon black which is the component parts of semiconducting shield in underground power transmission cable. Specimens were made of sheet form with the nine of specimens for measurement. Volume resistivity of specimens was measured by volume resistivity meter after 10 minutes in the preheated oven of both 25$\pm$1[$^{\circ}C$] and 90$\pm$1[$^{\circ}C$]. And specific heat (Cp) and thermal conductivity were measured by Nano Flash Diffusivity and DSC (Differential Scanning Calorimetry). The measurement temperature ranges of specific heat using the BSC was from 20[$^{\circ}C$] to 60[$^{\circ}C$], and the heating rate was 1[$^{\circ}C$/min]. And the measurement temperatures of thermal conductivity using Nano Flash Diffusivity were both 25[$^{\circ}C$] and 55[$^{\circ}C$]. Volume resistivity was high according to an increment of the content of carbon black from these experimental results. And specific heat was decreased, while thermal conductivity was increased by an increment of the content of carbon black. And both specific heat and thermal conductivity were increased by heating rate because volume of materials was expanded according to rise in temperature.

• Elastomers and Composites
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• 제50권2호
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• pp.92-97
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• 2015

A study on reaction kinetics for a PTMG/TDI prepolymer with 2,2'-dichloro-4,4'-methylenedianiline (MOCA), of which formulations may be generally used for fabricating high performance polyurethane elastomers, was peformed using non-isothermal differential scanning calorimetry (DSC). A number of thermograms were obtained at several constant heating rates, and analysed using Flynn-Wall-Ozawa (FWO) isoconversional method for activation energy, $E_a$ and extended-Avrami equation for reaction order, n. Urea formation reaction of the present system was observed to occur through the simple exothermic reaction process in the temperature range of $100{\sim}130^{\circ}C$ for the heating rate of $3{\sim}7^{\circ}C/min$. and could be well-fitted with generalized sigmoid function. Though activation energy was nearly constant as $53.0{\pm}0.5kJ/mol$, it tended to increase a little at initial stage, but it decreases at later stage by the transformation into diffusion-controlled reaction due to the increased viscosity. Reaction order was evaluated as about 2.8, which was somewhat higher than the generally well-known $2^{nd}$ order values for the various urea reactions. Both the reaction order and reaction rate explicitly increased with temperature, which was considered as the indication of occurring the side reactions such as allophanate or biuret formation.

• 대한화장품학회지
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• 제50권1호
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• pp.11-18
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• 2024

최근에 모발 케어 화장품 효능으로서 모발 보습 효과를 소구하려는 시도가 있지만 아직까지 모발 수분 추출을 어떤 온도에서 진행해야 하는지 평가법이 정해져 있지 않아 공인된 인체시험 평가가 없는 실정이다. 모발 수분 정량평가법을 확립하기 위해서 본 연구는 진행되었다. 모발 수분의 거동 패턴을 확인하기 위해 할로겐 수분 분석기로 온도를 다르게 하여 모발에 열을 가할 경우 수분 검출량은 가열 온도가 증가하면 계속 늘어나는 것을 확인하였다. 시차주사열량계로 모발의 흡열 반응 에너지를 평가한 결과 75 ℃ 부근에서 급격한 흡열 반응이 일어나는 특이한 현상을 관찰하였다. 인종별로 다른 모발에서도 이 현상은 관찰되었다. 모발 큐티클 장벽을 산화, 열로 손상시킨 모발에서는 급격히 상승하는 이 흡열 반응 온도가 조금 더 높은 77 ℃에서 일어났고, 이 모발을 극성오일 또는, 컨디셔닝 폴리머나 케라틴 단백질로 도포한 경우에는 73 ℃에서 관찰되었다. 이 반응이 모발 표면에서 어떤 영향을 미치는지 알아보기 위해서 원자현미경으로 마찰력을 관찰한 결과 75 ℃ 보다 높은 온도에서 가열할 때 큐티클 마찰력이 상승하고 그보다 높은 90 ℃에서는 변화가 없는 것을 관찰하였다. 마침내 75 ℃ 근처가 모발에 결합된 수분 분자의 탈착이 본격적으로 일어나는 임계온도임을 결론내렸다. 이를 통해 모발 수분을 검출해서 정량화하기 위한 조건으로 75 ℃가 가열온도로 최적합하고 이 때 검출된 수분량 10% 가량이 모발 케어 화장품 처리 전과 후를 비교할 수 있는 모발 수분 정량 기준값이 될 수 있음을 제시하였다.