• Transactions of the Korean Society of Mechanical Engineers B
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• v.38 no.8
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• pp.695-700
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• 2014

In the present study, the melting temperature depression of Sn nanoparticles manufactured using the modified evaporation method was investigated. For this purpose, a modified evaporation method with mass productivity was developed. Using the manufacturing process, Sn nanoparticles of 10 nm size was manufactured in benzyl alcohol solution to prevent oxidation. To examine the morphology and size distribution of the nanonoparticles, a transmission electron microscope was used. The melting temperature of the Sn nanoparticles was measured using a Differential scanning calorimetry (DSC) which can calculate the endothermic energy during the phase changing process and an X-ray photoelectron spectroscopy (XPS) used for observing the manufactured Sn nanoparticle compound. The melting temperature of the Sn nanoparticles was observed to be $129^{\circ}C$, which is $44^{\circ}C$ lower than that of the bulk material. Finally, the melting temperature was compared with the Gibbs Thomson and Lai's equations, which can predict the melting temperature according to the particle size. Based on the experimental results, the melting temperature of the Sn nanoparticles was found to match well with those recommended by the Lai's equation.

• Polymer Science and Technology
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• v.15 no.4
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• pp.449-456
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• 2004

이온성 액체 (ionic liquid)는 유기 양이온과 유기 (또는 무기) 음이온으로 이루어진 화합물이다. 이온들이 작아, 서로 가깝게 packing되어 있는 일반 이온성 염 (상온에서 고체상)과는 다르게, 이온성 액체는 양이온과 음이온의 크기가 상대적으로 커서, packing이 잘 되지 않아 낮은 lattice energy를 갖고 있게 되어,$^1$ 10$0^{\circ}C$나 그 이하의 낮은 녹는점을 갖는 염이다. 녹는점, 밀도, 점도, 친수성 및 소수성 특성은 주어진 이온성 액체의 양이온과 음이온을 적절히 선택하면 얼마든지 조절할 수 있어, 이온성 액체를 des구nor solvent로 부르고 있다.(중략)

• Proceedings of the Korea Crystallographic Association Conference
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• 2002.11a
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• pp.26-26
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• 2002

Cholesteryl 2,4-dichlorobenzoate의 결정은 두가지 서로 다른 결정구조로 결정화한다. Dichloromethane 용매에서 키운 결정(1)과 hexane 용매에서 키운 결정(2)이 서로 다른 구조를 나타낸다. Cholesterol O(3)에 결합한 dichloro- benzoate의 상대적인 배열도 이 두가지 구조에서 서로 다르다. 특히 이들 결정구조들은, 공간군(P2₁2₁2₁)과 격자상수들이 매우 비슷한 결정이다. 결정(1)은 뚜렷한 layer structure를 보여준다. 결정(1)은 예측한 대로 liquid crystalline state(cholesteric phase)가 130.8℃에서 나타내고 녹는점은 132.5℃이다. 결정(2)의 녹는점은 133.7℃이다.

• Journal of the Korean Chemical Society
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• v.46 no.3
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• pp.252-264
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• 2002

In this study, the experimental apparatus for boiling point and melting point in science textbooks of various curriculums were analyzed. Science teachers' views on the difference between the experimental value and the value written in textbooks were inquired, too. Their views on the experimental apparatus, nd results of freezing point,melting point, boiling point, fractional distillation, and thermometer calibration were also investigated. The results of this study showed that the types of experimental apparatus for boiling point and melting point were somewhat dif-ferent with science textbooks and curriculum. The teachers' views were also various according to their background. In the experiment of the fractional distillat ion, a large number of teachers recognized mismatch between the exper-imental value and the value written in textbooks as mistake of textbook contents or problem of experiment itself. The teachers of chemistry background take higher recognition of the requirement of thermometer calibration than those of non-chemistry background in middle school.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.19 no.12
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• pp.883-888
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• 2007

As a starting point of investigating what molecular dynamic simulations can reveal about the nature of atomic level of heating and cooling process, argon described by the LJ potential is considered. Stepwise heating and cooling of constant rates are simulated in the NPT (constant number, pressure and temperature) ensemble. Hysteresis is found due to the superheating and supercooling. Drastic change of volume and energy is involved with phase change, but the melting point can not be obtained by simply observing the changes of these quantities. Since liquid and solid phases can co-exist at the same temperature, Gibbs free energy should be calculated to find the temperature where the Gibbs free energy of liquid is equal to that of the solid since the equilibrium state is the state of minimum Gibbs free energy. The obtained melting temperature, $T^*=0.685$, is close to that of the experiment with only 2% error.

• Journal of the Korean Chemical Society
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• v.32 no.3
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• pp.276-284
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• 1988

The crystallization behaviours of poly(ethylene terephthalate) modified by 1, 3-propane diol, 1, 5-pentane diol, 1, 6-hexane diol, or poly(ethylene glycol) of molecular weight 300 as a third component were studied by isothermal and nonisothermal crystallization. When the content of the third diol was about 4 mol %, the isothermal crystallization rate at the same supercooling below the melting temperature and the nonisothermal crystallization rate at the same overheating above the glass transition temperature were increased more by the shorter flexible diol unit. On the contrary the nonisothermal crystallization rate at the same supercooling below the melting temperature was increased more by the longer flexible diol unit.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.32 no.6
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• pp.774-778
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• 1999

Tee yields, physical properties and gel formation abilities or hot-water extractable material (HWEM) and water-soluble alginate (WSA) extracted from Laminaria japonica were estimated and compared with those of the alginate (ASA) extracted with alkali solution in the routine procedure. The contents of HWEM, WSA and ASA in Laminaria japonica were 8.3, 2.5 and $19.1\%$, respectively. The HWEM and WSA had no gel formation ability, whereas the ASA had a good gol formation ability. The HWEM and WSA were almost not viscous even in $1.5\%$ of the sample solution, whereas the ASA was very highly viscous in above $0.5\%$ of sample solution. The melting points of $1\%$ solution of HWEM, WSA and ASA sample were 31, 24 and $14^{\circ}C$, respectively. The solubility at melting point of each samples varied from 2.3 to 2.6 g/100 g water, and a few differences were observed.

• Korean Journal of Food Science and Technology
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• v.22 no.6
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• pp.681-685
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• 1990

Changes in the physicochemical characteristics and trans acid of cottonseed oil under the condition of selective hydrogenation, temperature$210^{\circ}C,\;H_2\;pressure\;0.3\;kg/cm^2$ Ni catalyst amount 0.12% (in oil), agitation speed 280 rpm, were investigated. The saturated fatty acid such as palmitic acid and stearic acid did not show any difference, while linoleic acid($50.03%{\rightarrow}9.38%$) were transformed to oleic acid ($20.65%{\rightarrow}60.35%$) during hydrogenation. In linoleic acid isomers, cc form were reduced significantly, but ct, tc, tt form showed little change, respectively. In oleic acid isomer, t form increased markedly, whereas there was no significant difference in c form. Meanwhile, melting point(MP) and solid fat content (SFC) were linearly increased, but iodine value(IV) linearly decreased as hydrogenation proceeded. From these results, linear regression equations were obtained as follows. MP & IV : Y= 1.59-2.36X(r=-0.96, p<0.05), SFC($at\;20^{\circ}C$) & MP : Y=2.81+2.01X(r=0.96, p<0.05), SFC($at\;20^{\circ}C$) & IV : Y=9.40-5.16X(r=-0.99, p<0.01), SFC($at\;20^{\circ}C$) & 18 : 1t : Y=6.25+8.48X(r=0.97, p<0.05)

• 기계와재료
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• v.21 no.4
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• pp.30-37
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• 2010

최근 산업의 고도화에 따른 부품 소재의 고성능화에 따라 기존의 고온 세라믹의 한계를 극복하기 위한 노력으로 초고온 세라믹 재료에 대한 활발한 연구가 진행되고 있다. 초고온 세라믹은 대부분 붕화물이나 탄화물인 비산화물 세라믹으로 3000도 이상의 녹는점을 갖으며 2000도 부근에서는 사용을 목표로 하고 있다. 이 재료는 다른 세라믹들과 마찬가지로 취성파괴 거동을 나타내며, 이를 보완하기 위한 섬유강화 복합재료화도 활발히 진행되고 있다. 본고에서는 고온용 세라믹 장섬유와 세라믹 복합재료, 그리고 초고온 세라믹의 개발 현황과 산업화 전망을 정리하였다. 또한 초고온 세라믹의 발전 방향을 전망하였으며, 재료연구소에서 수행중인 초고온 세라믹의 연구 활동에 대해 간략히 언급하였다.

• Journal of the Society of Disaster Information
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• v.16 no.2
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• pp.383-391
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• 2020

Purpose: To identify internal self ignition and ignition caused by external flames in energy storage rooms, and to analyze the difference between ignition due to overheating and ignition caused by external heat sources. Method: membrane melting point measurement, battery external hydrothermal experiment, battery overcharge experiment, comparative analysis of electrode plate during combustion by overcharge and external heat, overcharge combustion characteristics, external hydrothermal fire combustion characteristics, 3.4 (electrode plate comparison) / 3.5 (overcharge) /3.6 (external sequence) analysis experiment. Result: Since the temperature difference was very different depending on the position of the sensor until the fire occurred, it is judged that two temperature sensors per module are not enough to prevent the fire through temperature control in advance. Conclusion: The short circuit acts as an ignition source and ignites the mixed gas, causing a gas explosion. The electrode breaks finely due to the explosion pressure, and the powder-like lithium oxide is sparked like a firecracker by the flame reaction.