• Journal of the Korean Ceramic Society
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• v.53 no.6
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• pp.700-706
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• 2016

Etch rate, surface roughness and microstructure as plasma resistance were evaluated for six kinds of oxide glass with different compositions. Borosilicate glass (BS) was found to be etched at the highest etch rate and zinc aluminum phosphate glass (ZAP) showed a relatively lower etch rate than borosilicate. On the other hand, the etching rate of calcium aluminosilicate glass (CAS) was measured to be similar to that of sintered alumina while yttrium aluminosilicate glass (YAS) showed the lowest etch rate. Such different etch rates by mixture plasma as a function of glass compositions was dependent on whether or not fluoride compounds were formed on glass and sublimated in high vacuum. Especially, in view that $CaF_2$ and $YF_3$ with high sublimation points were formed on the surface of CAS and YAS glasses, both CAS and YAS glasses were considered to be a good candidate for protective coating materials on the damaged polycrystalline ceramics parts in semi-conductor and display processes.

• Journal of the Korean housing association
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• v.23 no.1
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• pp.19-26
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• 2012

This study examines how fence demolition may change the thermal environments of external spaces of houses and suggests what factors need to be considered when a fence is demolished. The results of the research are summarized as follows. In terms of the surface temperature, there was no significant difference in all time plots after the removal of all materials. However, applying greening methods (changing the surface materials, planting trees, and building a green roof following fence demolition) could lower the surface temperatures, calling for proper plans for various greening methods. The MRT results indicates that walls block solar radiation and provide shade, reducing radiant heat from roads and surrounding structures during the daytime when solar radiation directly effects surface temperatures. Also, the application of greening methods such as planting vegetation and trees could have shading and evapotranspiration effects, leading to a lower temperature distribution. The HIP results were similar to the MRT results. They indicated that walls block solar radiation within the residential sections and provide shade, resulting in a lower temperature distribution during the daytime. However, areas where greening methods such as a green roof or tree planting were applied showed $1{\sim}2^{\circ}C$ difference in temperature distribution.

• Journal of the Korean Society of Food Science and Nutrition
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• v.34 no.2
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• pp.219-222
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• 2005

Some structural characteristics of hot-water soluble and insoluble starches (waxy black rice starch) were investigated. The hot-water soluble material content of waxy black rice starch was higher (16.6%) than that (13.4%) of Shinsunchalbyeo starch heated at 98$^{\circ}C$ for 8 min. The Amax and absorbance at 625 nm for hot-water soluble and insoluble material of waxy black rice starch were lower than those of Shinsunchalbyeo. Elution patterns of hot water soluble and insoluble materials by gel permeation chromatography (Sepharose CL-2B) were similar in both samples.

• Bulletin of the Korean Chemical Society
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• v.35 no.4
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• pp.989-993
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• 2014

The molecular structures of 2,6-diaza-1,3,5,7-tetraoxaspiro[3,3]heptane (1) and its dinitro derivative, 2,6-dinitro-2,6-diaza-1,3,5,7-tetraoxaspiro[3,3]heptane (2), were fully optimized without symmetry constraints at $HF/6-31G^*$ level of theory. A bisected conformation with respect to the ring is preferred with a $C_2$ symmetric structure. The density of each molecule in the crystalline state was estimated to 1.12 and 2.36 $g/cm^3$ using PM3/VSTO-3G calculations from the molecular volume. The heat of formation was calculated for two compounds at the CBS-4M level of theory. The detonation parameters were computed using the EXPLO5 software: D = 6282 m/s, $P_{C-J}$ = 127 kbar for compound 1, D = 7871 m/s, $P_{C-J}$ = 307 kbar for compound 2, and D = 6975 m/s, $P_{C-J}$ = 170 kbar for 60% compound 2 with 40% TNT. Specific impulse of compound 1 in aluminized formulation when used as monopropellants was very similar to that of the conventional ammonium perchlorate in the same formulation of aluminum.

• Journal of the Korean Society of Costume
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• v.60 no.4
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• pp.98-112
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• 2010

This study is on the 18th-century man's clothing excavated from Mr. Kim(1683-1766)'s tomb in Cheongju, Chungbuk in 2003. There are more than 100 pieces of excavated costumes from the tomb of Won-taek Kim. The excavated costumes have the value of genuine materials. Among them, 36 garments in good condition were investigated. As a result, there are several kinds of the excavated coats with different sizes, depending on the type of coats-Simui(深衣), Danryeong(團領), Sagyusam(四揆衫), Daechang, jungchimak(中赤莫), and Sochangui. These different-size coats reveal the degree of ritual; the length of the ritual costume is longer than that of the daily one. We can see two kinds (large and small) of coats, jackets, and pants. The large-size clothing is for the dead, the small size one as daily clothing was used for filling the empty space of the coffin. Among the excavated clothing from Mr. Kim's tomb, clothing for the dead(shroud) is bigger than man's daily costume. Concerning the form, color, and materials of the costumes, clothing for the dead is similar to daily clothing, while there is the difference in their size. The oversized costumes of coats, jackets, and pants are also different in size, matching the structure of clothing.

• Composites Research
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• v.12 no.2
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• pp.1-9
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• 1999

The piezoelectric material connected to external electric networks possesses frequency dependent stiffness and loss factor which are also affected by the shunting circuit. The external electric networks are generally specialized for two shunting circuits: one is the case of a resistor alone and the other is the combination of a resistor and an inductor. For resistive shunting, the material properties exhibit frequency dependency similar to viscoelastic materials, but are much stiffer and more independent of temperature. Shunting with a resistor and inductor introduces an electrical resonance, which can change the characteristics of structural resonance optimally in a manner analogous to a PMD (proof mass damper). Passive damping enhancement of composite beam using piezoelectric material connected to external electrical networks is achieved and presented in this paper.

• Advances in materials Research
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• v.1 no.1
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• pp.31-35
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• 2012

Unique tooth-like (milky white) color ${\beta}$-Ti dental arch wires are prepared by anodization in a 1M $H_2SO_4$ electrolyte at $30^{\circ}C$ and 30 V for 88 min and 40 s. Aggregates are formed on these surfaces of the anodized wires with tooth-like colors, and the results are different from those of the anodized wires with monochromatic colors which have smooth oxide surfaces. Similar to the monochromatic wires, the composition of the oxide layer is $TiO_{2-x}$ and the x approaches zero at the outer layer. But different from the amorphous structure observed in monochromatic wires, the oxide layers are partially crystallized with an anatase structure. The milky white colors result from the rough and crystalized oxide layers, not by the interference effect as observed in monochromatic wires.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.31 no.6 s.261
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• pp.710-717
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• 2007

This paper presents plastic limit loads and approximate J-integral estimates for circumferential part-through surface crack at the interface between elbows and pipes. Based on finite element limit analyses using elastic-perfectly plastic materials, plastic limit moments under in-plane bending are obtained and it is found that they are similar those for circumferential part-through surface cracks in the center of elbow. Based on present FE results, closed-form limit load solutions are proposed. Welds are not explicitly considered and all materials are assumed to be homogeneous. And the method to estimate the elastic-plastic J-integral for circumferential part-through surface cracks at the interface between elbows and straight pipes is proposed based on the reference stress approach, which was compared with corresponding solutions fur straight pipes.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.9 no.6
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• pp.170-177
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• 2000

Dense $Al_2$O$_3$-30%TiC and Si$_3$N$_4$ ceramic tool materials with various grain size were produced by sintering-HIP treatment and by gas-pressure sintering. The fracture toughness was measured by indentation fracture and indentation strength method for both ceramics with various grain size. The effect of the grain size on the fracture toughness was evaluated, and the correlation between fracture toughness and mechanical properties such as hardness, Young\`s modulus and flexural strength of these ceramic were also investigated. The highest fracture toughness of around 6.7 MPa.m(sup)1/2 was obtained in Si$_3$N$_4$ ceramics with grain size of 1.58${\mu}{\textrm}{m}$. With a larger grain size of $Al_2$O$_3$-30%TiC and Si$_3$N$_4$ ceramics, the fracture toughness was generally increased. The increased fracture toughness of these ceramic also improved the flexural strength although the hardness decreased considerably. Similar results were obtained in grain size and mechanical properties on both $Al_2$O$_3$-30%TiC and Si$_3$N$_4$ ceramic tool materials.

• Journal of the Semiconductor & Display Technology
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• v.14 no.3
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• pp.7-11
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• 2015

In order to protect the patterned mask from contamination during lithography process, pellicle has become a critical component for Extreme Ultraviolet (EUV) lithography technology. According to EUV pellicle requirements, the pellicle should have high EUV transmittance and robust mechanical property. In this study, silicon nitride, which is well-known for its remarkable mechanical property, was used as a pellicle membrane material to achieve high EUV transmittance. Since long silicon wet etching process time aggravates notching effect causing stress concentration on the edge or corner of etched structure, the remaining membrane is prone to fracture at the end of etch process. To overcome this notching effect and attain high transmittance, we began preparing a rather thick (200 nm) $SiN_x$ membrane which can be stably manufactured and was thinned into 43 nm thickness with HF wet etching process. The measured EUV transmittance shows similar values to the simulated result. Therefore, the result shows possibilities of HF thinning processes for $SiN_x$ EUV pellicle fabrication.