• Journal of the Korean Society of Safety
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• v.30 no.4
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• pp.8-13
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• 2015

The magnetic shape memory alloys have recently received a lot of attention due to the considerable progress achieved in understanding the particular importance and the development of the factors. Among these alloys, the ferromagnetic Co-Ni- alloys have been concerned specially because of the thermoelastic character of the fcc (g) - bct (a) martensitic transformation which exhibits under the action of the temperature (shape memory effect), the stress (superelasticity) and the magnetic field (magnetoelasticity). The morphological, the crystallographical, and the thermal characteristics of thermally induced martensite in Co-35.3Ni-11.3Al(wt.%) and Co-28.1Ni-47.4Fe-3.3Ti (wt.%) alloy have been investigated by the scanning electron microscope (SEM), the X-ray Diffraction (XRD), and the differential scanning calorimeter (DSC).

• Proceedings of the KOSOMBE Conference
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• v.1989 no.05
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• pp.9-12
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• 1989

A preliminary study has been conducted to demonstrate the effect of laser heat treatment on Ni Ti alloy dental arch wires ($0.016"\;{\times}\;0.022"$ and $0.018"\;{\times}\;0.026"$, rectangular shape). Changes in mechanical and thermal properties and surface morphologies are investigated by using optical and scanning electron microscope (SEM), energy dispersive x-ray microprobe analysis(EDX), differential scanning calorimeter (DSC), and micro hardness tester. The results indicate that the laser can affect the thermal equilibrium state of the localized surface. Titanium rich surface film is formed by the laser treatment. The surface film and rapidly resolidified underlying structures show better chemical resistance than the matrix material. Phase transition temperatures which are related to shape recovery temperatures are changed after laser treatment. Hardness of resolidified area and heat affected zone are lower than before treatment.

• Journal of the Korean Society of Safety
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• v.17 no.4
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• pp.133-139
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• 2002

Core-shell polymers of inorganic/organic pair, which are consisted of both core and shell component, were synthesized by sequential emulsion polymerization using ethyl methacrylate (EMA) as a shell monomer and ammonium persulfate as initiator. We found that $CaCO_3$ core should be prepared by adding 2.0wt% SDBS(sodium dodecyl benzene sulfonate), $CaCO_3$ core/PEMA shell polymerization was carried out on the surface of $CaCO_3$ particle during EMA shell polymerization in the core-shell polymer preparation. The structure of core-shell polymer were investigated by measuring the degree on decomposition of $CaCO_3$ by HCI solution, thermal decomposition of polymer composite on thermogravimetric analyzer, glass transition temperature on differential scanning calorimeter, and morphology using scanning electron microscope.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.8 no.3
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• pp.435-441
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• 1998

Li-SGICs as a anode of lithium ion battery were synthesized by high-pressure method as a function of the Li-contents. The characteristics of these prepared compounds were determined from the studies with X-ray diffraction method and differential scanning calorimeter (DSC) analysis. From the results of X-ray diffraction, it was found that the lower stage intercalation compounds were formed with increase of Li-contents. The mixed stages in these compounds were also observed. In the case of the $Li_{30;wt%}$-SGIC, the compounds in the stage 1 structure were formed predominantly, but the structure of only pure stage 1, due to the structural defect of synthetic graphite, was not observed. The enthalpy and entropy changes of the compounds could be obtained from the differential scanning calorimetric analysis results. From the results, it was found that exothermic and endothermic reactions of Li-SGICs are related to thermal stability of lithium between artificial graphite layers.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.26 no.1
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• pp.21-25
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• 1993

In order to obtain the fundamental factors influencing on gelation of Alaska pollack meat paste during processing, thermograms of protein using differential scanning calorimetry (DSC) were investigated. The thermal transition temperatures of Alaska pollack meat paste due to protein denaturation were $38^{\circ}C,\;49^{\circ}C,\;55^{\circ}C\;and\;77^{\circ}C$, but those temperatures were changed to $35^{\circ}C,\;45^{\circ}C,\;50^{\circ}C\;and\;73^{\circ}C$ after adding salt($3\%$ NaCl). The starch did not affect the thermal transition of fish protein and its thermal properties were changed independently in starch-meat paste mixture system.

• Korean Journal of Materials Research
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• v.10 no.3
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• pp.184-190
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• 2000

We investigated the effect of filler content on the thermo-mechanical properties of modified ACA composite materials by incorporation of non-conducting fillers and the reliability of flip chip assembly on organic substrates using modified ACA composite materials. For the characterization of modified ACA s composites with different content of non-conducting fillers, differential scanning calorimeter (DSC), and thermo-gravimetric analyzer (TGA), dynamic mechanical analyzer (DMA), and thermo-mechnical analyzer (TMA) were utilized. As the non-conducting filler content increased, CTE values decreased and storage modulus at room temperature increased. In addition, the increase in the content of filler brought about the increase of Tg^{DSC}$ and $Tg^{TMA}$. However, the TGA behaviors stayed almost the same. Contact resistance changes were measured during reliability tests such as thermal cycling, high humidity and temperature, and high temperature at dry condition. It was observed that reliability results were significantly affected by CTEs of ACA materials especially at the thermal cycling test. Results showed that flip chip assembly using modified ACA composites with lower CTEs and higher modulus by loading non-conducting fillers exhibited better contact resistance behavior than conventional ACAs without non-conducting fillers.

• Composites Research
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• v.35 no.3
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• pp.147-152
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• 2022

Low-temperature characteristics according to internal temperature conditions during rotational molding of Type 4 pressure vessel liners were studied in this paper. Since rotational molding has a sensitive effect on the formability of the liner depending on the temperature conditions, the temperature conditions for the polyamide used should be accurately set. The structural changes of polyamide as the liner material was analyzed the surface by atomic force microscope (AFM), and the crystallinity measured with a differential scanning calorimeter (DSC) is used to evaluate the change of the mechanical strength value at low temperature. In addition, the formability of the liner was confirmed by observation of the yellow index inside the liner. As a result, as the melting range of the internal temperature becomes wider, the yellow index shows a lower value, and the elongation and impact characteristics at low temperatures are improved. It was also confirmed that the structure of the polyamide was uniform and the crystallinity was high by AFM and DSC. These experimental results contribute to the improvement of characteristics at low temperatures due to changes in temperature conditions during rotational molding.

• Journal of Conservation Science
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• v.28 no.2
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• pp.131-139
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• 2012

The exothermic cure kinetics of epoxy resin was controlled by hardener containing fast and slow curing agents. The epoxy risen comprises hydrogenated bisphenol A-based epoxide (HBA), fast curing agent (FH) and slow curing agent poly(propyleneglycol)bis(2-aminopropylether) (SH). Talc was used as an inorganic additive. In the process of curing, cure kinetics along with temperature was monitored by differential scanning calorimeter (DSC) and thermocouple to show that the temperature increase was well controlled by adjusting the hardener mixture. Additionally, bending and tensile strengths of the epoxy/talc composites were also measured to be lower and higher with the amount of the talc inorganic additive, respectively. It is thus concluded that the increase in the temperature during exothermic curing reaction and mechanical properties of epoxy resins are tuned by optimizing hardener mixture for successful stone conservation.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.30 no.4
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• pp.204-209
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• 2017

Thermal and structural stability in the glass transition region of chalcogenide glasses has been investigated in terms of thermodynamics for application to various optoelectronic devices. In this study, the compositions of $Ge_xSb_{20}Se_{80-x}$ (x = 10, 15, 20, 25, and 30) were selected to investigate the glass stability according to germanium ratios. The chalcogenide bulks were fabricated by using a traditional melt-quenching method. Thin films were deposited by a thermal evaporation system, maintaining the deposition ratio of $3{\sim}5{\AA}$ in order to have uniformity. The thermal and structural properties were measured by a differential scanning calorimeter (DSC) and X-ray diffraction (XRD). The DSC analysis provided thermal parameters and theoretical glass region stabilities. The XRD analysis supported the theoretical stabilities because of where the crystallization peak data occurred.

• Polymer(Korea)
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• v.25 no.5
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• pp.617-624
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• 2001

The core-shell composite latexes were synthesized by stage emulsion polymerization of methyl methacrylate (MMA) and styrene (St) with ammonium persulfate after preparing monomer pre-emulsion in the presence of anionic surfactant. However, in preparation of core-shell composite latex, several unexpected results are observed, such as, particle coagulation, low degree of polymerization, and formation of new particles during shell polymerization. To solve the disadvantages, We study the effect of initiator concentrations, surfactant concentrations, and reaction temperature on the core-shell structure of polymethyl methacrylate/polystyrene and polystyrene/polymethyl methacrylate. Particle size and particle size distribution were measured using particle size analyzer, and the morphology of the core-shell composite latex was determined using transmission electron microscope. Glass temperature was also measured using differential scanning calorimeter. To identify the core-shell structure, pH of the two composite latex solutions were measured.