• Journal of Information Display
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• v.11 no.4
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• pp.135-139
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• 2010

A series of Sr-Si-S compounds was synthesized using an advanced chemical method in which the use of one solution-based process uniformly dispersed the $Eu^{2+}$ activators in the host crystals, to find new compositions that would suit phosphor applications. Particular focus was given to the Si-rich region. This led to the synthesis of a single-phase compound that showed an unknown X-ray diffraction pattern. This compound had a composition close to that of $SrSi_2S_5$. When this compound is activated with $Eu^{2+}$ ($SrSi_2S_5:Eu^{2+}$), it shows a cyan-blue emission with a main luminescence peak at 495 nm. This emission is excited by wavelengths of 250-440 nm and has a maximum excitation at 350 nm.

• Macromolecular Research
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• v.16 no.5
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• pp.434-440
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• 2008

Three-armed, star-shaped molecules containing 4-(N,N-diphenyl)amino-4'-nitroazobenzene chromophores were synthesized to study the diffraction behavior after inscribing surface relief gratings. The two molecules differed in terms of their mode of chromophore attachment to the core. In compound 5, they were bound to the core laterally through alkylene spacers, whereas the chromophores were tethered perpendicularly to the core in compound 4. Although 60 wt% of the polar azobenzene chromophores was comprised of large molecules, no aggregation behavior was observed in the absorption spectra of the thin films. The surface relief gratings were elaborated on the surface of the molecular films by the two-beam interference method. The dynamics of grating formation were studied in terms of the diffraction efficiency using two different film samples made up of two star-shaped molecules. The maximum diffraction efficiency of D-$(ENAZ)_3$, compound 4, was measured to be about 30%, which was significantly high. The mode of chromophore attachment affected the dynamic properties of the diffraction gratings.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09a
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• pp.480-481
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• 2006

The n-type $(95%Bi_2Te_3-5%Bi_2Se_3)$ compound was newly fabricated by gas atomization and hot extrusion, which is considered to be a mass production technique of this alloy. The effect of powder size on thermoelectric properties of 0.04% $SbI_3$ doped $95%Bi_2Te_3-5%Bi_2Se_3$ alloy were investigated. Seebeck coefficient $({\alpha})$ and Electrical resistivity $(\rho)$ increased with increasing powder size due to the decrease in carrier concentration by oxygen content. With increasing powder size, the compressive strength of $95%Bi_2Te_3-5%Bi_2Se_3$ alloy was increased due to the relative high density. The compound with ${\sim}300\;{\mu}m$ size shows the highest power factor among the four different powder sizes. The rapidly solidified and hot extruded compound using $200[\sim}300{\mu}m$ powder size shows the highest compressive strength.

• Proceedings of the Korean Magnestics Society Conference
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• 2003.12a
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• pp.286-286
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• 2003

• Proceedings of the Materials Research Society of Korea Conference
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• 2003.03a
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• pp.177-177
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• 2003

• Journal of Korea Foundry Society
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• v.26 no.3
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• pp.123-128
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• 2006

Mechanical and thermal properties of spray-cast hypereutectic Al-20wt.%Si-xwt.%Fe alloys (x=0, 1, 3, 5) were investigated. After the spray-casting, hot extrusion was performed at $400^{\circ}C$. Intermetallic compound (${\beta}-Al_5FeSi$) and primary Si are observed in the spray-cast aluminum alloys. The size of primary Si and intermetallic compound of the spray-aluminum alloys became finer and more uniformly distributed than that of the permanent mold cast ones. Ultimate tensile strength of the spray-cast aluminum alloys increased by increasing Fe contents, but that of the permanent mold cast aluminum alloys decreased by increasing Fe contents possibly due to increased amount of coarse intermatallic compound. The coefficient of thermal expansion (CTEs) of the aluminum alloys became lower with finer primary Si and intermetallic compound, and this is attributed to the increased amount of interfacial area between the aluminum matrix and the phases of finer Si and intermetallic compound.

• Steel and Composite Structures
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• v.38 no.1
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• pp.79-86
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• 2021

Due to the complex geological conditions, a large number of high quality coal seams was buried in the western of China which cannot be mining in open-pit methods. The dynamic properties of that coal cannot be studied easily in real site for the complex working condition. The compound coal blocks made on the basis of the real situation were studied in the laboratory. The physical and mechanical properties of the compound coal blocks and the raw coal were contrasted by using the UCS tests. The results show that the compound coal blocks made by mixing coal powder, cement and water in proportion of 2.5:2:1 are the closest to that of standard raw coal. Then the propagation of strain waves and crushing effects on the coal were studied in the compound coal blocks by using the super dynamic strain test system and the numerical calculated method of ANSYS/LS-DYNA. The results show that the diameter of the crushing zone in the compound coal blocks was similar to that in the numerical results. The fractures distribution in laboratory tests also has a similar trend to the calculation results. The measured strain waves at the distance of 50 cm, 100 cm, and 150 cm from the center of the charge are mainly concerned at -1.0×104 με and have a similar trend as that in the numerical simulation.

• Journal of the Korean Society for Heat Treatment
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• v.8 no.4
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• pp.289-301
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• 1995

The effect of Air/$C_3H_8$ gas addition on the compound layer growth of steels nitrocarburised in $NH_3+Air+C_3H_8$ mixed gas atmospheres was investigated. It is considered that amount of residual $NH_3$ was varied according to alternation of Air/$C_3H_8$ mixing ratio and volume content. The compound layer formed from nitrocarburising was composed of ${\varepsilon}-Fe_{2-3}$(C, N) and ${\gamma}^{\prime}-Fe_4$(C, N). According as Air/$C_3H_8$ mixing ratio increased, the superficial content of ${\gamma}^{\prime}-Fe_4$(C, N) within the compound layer was increased, at the same time the growth rate of compound layer and porous layer was increased. In the case of alloy steel at the fixed gas composition, the growth rate of compound layer and porous layer was worse than carbon steel and compound layer phase composition structure primarily consisted of E phase. As the carbon content of materials was increasing in the given gas atmospheres, the growth rate of compound layer and porous layer was increased and the superficial content of ${\varepsilon}-Fe_{2-3}$(C, N) within the compound layer was increased.

• Journal of the Korean Society for Heat Treatment
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• v.13 no.3
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• pp.143-150
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• 2000

Ferritic plasma nitrocarburising was performed on pure iron using a modified DC plasma unit. This investigation was carried out with various gas compositions which consisted of nitrogen, hydrogen and carbon monoxide gases, and various gas pressures for 3 hours at $570^{\circ}C$. After treatment, the different cooling rates(slow cooling and fast cooling) were used to investigate its effect on the structure of the compound layer. The ${\varepsilon}$ phase occupied the outer part of the compound layer and ${\gamma}^{\prime}$ phase existed between the ${\varepsilon}$ phase and the diffusion zone. The gas composition of the atmosphere influenced the constitution of the compound layer produced, i.e. high nitrogen contents were essential for the production of ${\varepsilon}$ phase compound layer. It was found that with increasing carbon content in the gas mixture the compound layer thickness increased up to 10%. In the gas pressure around 3 mbar, the compound layer characteristics were slightly effected by gas pressure. However, in the low gas pressure and high gas pressure, the compound layer characteristics were significantly changed. The constitution of the compound layer was altered by varying the cooling rate. A large amount of ${\gamma}^{\prime}$ phase was transformed from the ${\varepsilon}$ phase during slow cooling.

• The Journal of Korean Academy of Prosthodontics
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• v.38 no.5
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• pp.650-658
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• 2000

This study was investigated to compare the bond strength of polysulfide adhesive between tray resin and border molding materials and to evaluate the effect of saliva contamination on them. We made the 135 resin tray secimens with a dimension of $1{\times}1{\times}1cm$ and divided them into 3 groups by the materials 1) Quicky group, 2) Compound group, and 3) Impregum group Each group was subdivided by saliva contimination. Group S1 : applied adhesive without saliva contamination Group S2 : applied adhesive after drying 15seconds after saliva contamination Group S3 : applied adhesive no after saliva contamination. Tensile tests were performed with a Universal Load testing machine. Results showed Impregum group significantly higher bond strength than Quicky group, but there was no significant difference in adhesive bond strength between Compound group and Quicky group in experimental group by materials In experimental group by saliva contamination, S1 group is significantly higher bond strength than S2 group and S2 group is significantly higher bond strength than S3 group in Quicky group and S1, S2 group is significantly higher bond strength than S3 group in Compound group and Impregum group. Impression compound and Impregum F which are usually used as an individual tray border mold-ing material can be said to be satisfied in adhesive bond strength to polysulfide impression materials. After try-in and clinical adjustment are performed, a custom tray should be properly rinsed and air dried before tray adhesive was placed.