• 열처리공학회지
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• 제29권2호
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• pp.51-55
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• 2016

The P/M processing of titanium aluminide using amorphous TiAl is developed by which it is possible to overcome inherent fabricability problems and to obtain a fine microstructure. A high quality amorphous TiAl powder produced by reaction ball milling shows clear glass transition far below a temperature at the onset of crystallization in differential scanning calorimetry above a heating rate of 0.05 K/s. We obtained a fully dense compact of amorphous TiAl powders, encapsulated in a vacuumed can, via viscous flow by hot isostatic pressing (HIP). Isothermally annealing of HIP'ed amorphous compact under a pressure of 196 MPa shows a progressive growth of ${\gamma}-TiAl$ phase with ${\alpha}2$ ($Ti_3Al$), which is characterized by increasing sharpness of X-ray peaks with temperature. Fully dense HIP'ed compact of titanium aluminide TiAl shows a high hardness of 505 Hv, suggesting strengthening mechanisms by sub-micron sized grain of ${\gamma}-TiAl$ and particle-dispersion by second phase constituent, ${\alpha}2$.

• Macromolecular Research
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• 제13권3호
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• pp.212-217
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• 2005

The pyrolysis kinetics of polyurethanes synthesized from polycaprolactone diol (PCL) and diisocyanate (HDI, $H_{12}MDI$) using catalysts such as dibutyltin dilaurate (DBTDL) were studied by a thermogravimetric (TG) technique, which involved heating the sample at the rates of 10, 20 and $30^{\circ}C$/min. The effect of the kind of diisocyanate and the hard segment contents on the activation energy and reaction order were examined at conversions ranging from 1 to $100\%$. The activation energies at first increased slowly with increasing conversion. Also, differential scanning calorimetry (DSC) was used to investigate the structural differences in each polyurethane. DSC can reveal the melting behavior, in terms of the glass transition temperature ($T_g$), which is known to vary as a function of the stoichiometry and processing conditions.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제53권9호
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• pp.455-458
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• 2004

In this paper, we investigated impurities content and physical properties showing by changing the content of carbon black that is semiconductive materials for underground power transmission. Specimens were made of sheet form with the three of existing resins and the nine of specimens for measurement. Impurities content of specimens was measured by ICP-AES (Inductively Coupled Plasma Atomic Emission Spectrometer), and density of specimens were measured by density meter And then specific heat (Cp) was measured by DSC (Differential Scanning Calorimetry). A ranges of measurement temperature were from $0^{\circ}[C]$ to $200^{\circ}[C]$, and heating temperature was $4^{\circ}[C/min]$. Impurities content was highly measured according to increasing the content of carbon black from this experimental result, also density was increased according to these properties. Especially impurities content values of the Al and A2 of existing resins were measured more than 4000［ppm］. Specific heat from the DSC results was decreased according to increasing the content of carbon black. Because ionic impurities of carbon black having Fe, Co, Mn, Al and Zn are rapidly passed kinetic energy increasing the number of times breaking during the unit time with the near particles according to increasing vibration of particles by the applied heat energy.

• Elastomers and Composites
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• 제24권1호
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• pp.11-18
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• 1989

The thermal degradation of Poly(methyl methacrylate) (PMMA) and poly(acrylonitrile butadiene styrene)(ABS) terpolymer as well as their mixtures were carried out using the thermogravimetry and differential scanning calorimetry(DSC) in the stream of nitrogen and air with 50 ml/min at the various heating rate from 4 to $20^{\circ}C/min$ and temperature from 200 to $300^{\circ}C$ The values of activation energies of thermal degradation determined by TG and DSC in the various PMMA/ABS mixtures were $34{\sim}58Kcal/mol,\;35{\sim}54Kcal/mol$ in the stream of nitrogen. The values of activation energy of ABS20% mixture was appeared high in camparison with addition rule. According to increasing the composition of ABS, the temperatures of glass transition and initial decomposition temperature were increased. PMMA/ABS mixtures by the analysis of infrared spectrophotometer were decomposed by main chain scission in the stream of nitrogen.

• Preventive Nutrition and Food Science
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• 제15권4호
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• pp.356-359
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• 2010

Glass transition phenomena in nine Korean pure honeys (moisture content 18.3~20.1%) and honey-water mixtures by different water contents (0, 2, 5, and 10% w/w) were investigated with modulated different scanning calorimetry (MDSC). The total, reversing, and non-reversing heat flows were quantified during heating using MDSC. Glass transition was observed from reversing heat flow separated from the total heat flow. The glass transition temperatures ($T_g$) of pure honeys, which are in the range of $-42.7^{\circ}C$ to $-50.0^{\circ}C$, varied a lot with low determination coefficient ($R^2$=0.63), whereas those of honey-water mixtures decreased with a decrease in honey content. The $T_g$ values were also more significantly different among honey-water mixtures when compared to pure honeys, indicating that in the honey-water mixture system the $T_g$ values appear to be greatly dependent on moisture content. The measured heat capacity change (${\Delta}C_p$) was not influenced by moisture content.

• 센서학회지
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• 제6권6호
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• pp.500-507
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• 1997

형상기억 합금의 정밀한 동작 온도 조절을 위한 불순물의 종류에 따른 형상기억합금의 열처리 효과를 연구하였다. 급냉온도에 따른 전기 저항 측정으로 Cu-17.25Zn-15Al 및 Cu-17.25Zn-15Al-1Ag/Fe 의 열처리에 의한 마르텐사이트 변태온도의 변화를 측정하였다. 승온율에 따른 DSC(Differential scanning calorimeter) 측정으로 고온모상에서의 상전이 온도와 종류를 구별하였다. 그리고 XRD 측정으로 구조 변화를 관찰하였다. Cu-17.25Zn-15Al 합금에서 고온 모상의 규칙-불규칙 전이온도인 $T_{B2}$, $T_{L21}$은 각각 809K와 610K이고. Cu-17.25Zn-15Al-1Ag 및 Cu-17.25Zn-15Al-1Fe 시료의 $T_{B2}$, $T_{L21}$은 각각 794K, 610K 그리고 803K, 613K 이다. 모든 시료에서 $T_{B2}$ 근방에서의 급냉은 마그텐사이트. 변태온도를 높이지만 $T_{L21}$ 근방에서의 급냉은 마르텐사이트 변태온도를 낮춘다.

• 천문학회보
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• 제43권1호
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• pp.53.1-53.1
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• 2018

During a major solar eruption, the erupting plasma is possibly out of the equilibrium ionization state because of its rapid heating or cooling. The non-equilibrium ionization process is important in a rapidly evolving system where the thermodynamical time scale is shorter than the ionization or recombination time scales. We investigate the effects of non-equilibrium ionization on EUV and X-ray observations by the Atmospheric Imaging Assembly (AIA) on board Solar Dynamic Observatory and X-ray Telescope (XRT) on board Hinode. For the investigation, first, we find the emissivities for all the lines of ions of elements using CHIANTI 8.07, and then we find the temperature responses multiplying the emissivities by the effective area for each AIA and XRT passband. Second, we obtain the ion fractions using a time-dependent ionization model (Shen et al. 2015), which uses an eigenvalue method, for all the lines of ion, as a function of temperature, and a characteristic time scale, $n_et$, where $n_e$ and t are density and time, respectively. Lastly, the ion fractions are multiplied to the temperature response for each passband, which results in a 2D grid for each combination of temperature and the characteristic time scale. This is the set of passband responses for plasma that is rapidly ionized in a current sheet or a shock. We investigate an observed event which has a relatively large uncertainty in an analysis using a differential emission measure method assuming equilibrium ionization state. We verify whether the observed coronal plasmas are in non-equilibrium or equilibrium ionization state using the passband responses.

• Bulletin of the Korean Chemical Society
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• 제30권10호
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• pp.2253-2258
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• 2009

wet spun polyacrylonitrile (PAN) fiber precursors. The process variables chosen were treatment temperature, applied tension in stabilization process. The temperature profile of the stabilization was set on the basis of exothermic peaks of the differential scanning calorimetry (DSC) result. Both tensile strength and modulus increased with holding at onset temperatures of the exothermic peaks for extended duration, and with a higher heating rate up to the onset temperatures at a given applied tension among the experimental conditions. The increase in load monotonously increased the tensile modulus, on the other hand, the tensile strength was maximum at the load of 15 mg/filament (T15). The load 20 mg/ filament (T20) was considered to be exceeded to form oriented crystalline structure, possibly introducing more defects in the fiber than under load of T15. The sample CP3-T15 O5 H30 showed the best tensile properties among the samples experimented whose tensile properties are compatible with the commercialized grade of general purpose carbon fibers even at low carbonization temperature such as $800\;{^{\circ}C}$ (the carbonization temperature in the commercial process. 1300∼$1500\;{^{\circ}C}$).

• 전기전자학회논문지
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• 제23권1호
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• pp.295-301
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• 2019

바이오샘플의 DNA를 대량 증폭할 수 있는 휴대형 실시간 중합효소연쇄반응(Real-time PCR) 기기에서 히터는 PCR 반응 온도를 제어하기 위한 중요한 요소 중의 하나이다. 보통 빠른 히팅을 위해 소형 PCR 칩에 집적화되어 있고, 반도체 공정을 이용하여 박막형태로 제작되어 PCR 칩 제작 단가가 높은 편이다. 따라서 본 연구에서는 값싸고 온도제어를 정확히 할 수 있는 히터로 칩 저항을 사용하는 것을 제안한다. 칩 저항을 사용한 히터는 구조가 단순하고 제작이 쉽다는 장점이 있다. $2.54{\times}2.54cm^2$ 크기의 실시간 PCR 칩 위에 칩 저항을 1개 또는 2개를 사용했을 때 온도분포를 시뮬레이션 하였고, 고른 온도분포를 갖는 PCR 칩을 제작했다. 또한 효율적인 PCR 칩 냉각을 위해 소형 fan이 내장된 하우징을 설계하였고, 3D 프린터로 제작했다. 온도제어는 마이크로프로세서를 이용한 PID제어법(Proportional-Integral-Differential control)을 적용했다. 온도상승비와 하강비는 각각 $18^{\circ}C/s$, $3^{\circ}C/s$이며, 각 PCR 반응 단계의 유지 시간을 30초로 하였을 때, 한 사이클은 약 2.66분이 걸렸고, 35 사이클은 약 93 분 내로 진행할 수 있었다.

• Composites Research
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• 제30권6호
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• pp.350-355
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• 2017

Phenylcyclohexyl (PCH) mesogen을 diglycidyl terephthalate의 2,5 위치에 치환시킨 새로운 액정성 에폭시 수지를 설계하였다. 이 물질의 액정성은 DSC(differential scanning calorimetry)와 POM(polarized optical microscopy)으로 분석하였다. 모든 액정성 에폭시 유도체는 가열 및 냉각 시에 모두 smectic상을 나타내는 enantiotropic한 성질을 나타내었다. 액정성 에폭시의 공융 혼합물을 통하여 액정 온도구간을 확장시켰다. 경화된 신규 액정성 에폭시는 $0.4W{\cdot}m^{-1}{\cdot}K^{-1}$의 높은 열전도도를 나타냈다. 높은 열전도도를 갖는 신규 액정성 에폭시는 전자 및 디스플레이용 복합소재로 이용될 것으로 기대된다.