• Korean Journal of Materials Research
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• v.17 no.2
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• pp.68-72
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• 2007

Optimum compositions for piezoelectric properties of $(Bi_{0.5}Na_{0.5})_{(1-x)}Ba_xTiO_3$ ceramics were investigated in the range of $x=0{\sim}0.1$ covering rhombohedral to tetragonal phase regions. No impurity phases other than a perovskite phase were found and the grain size decreased with increasing x. A two-phase coexisting morphotropic phase area rather than boundary dividing rhombohedral and tetragonal phase regions appeared to exist at $x=0.05{\sim}0.08$. As for piezoelectric properties within morphotropic phase compositions, the piezoelectric constant ($d_{33}$) and the electromechanical coupling factor ($K_p$) showed peak values at x=0.065, 192 pC/N and 34%, respectively, indicating x=0.065 as an optimum composition for piezoelectric $(Bi_{0.5}Na_{0.5})_{(1-x)}Ba_xTiO_3$ ceramics.

• Journal of the Korean Dietetic Association
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• v.12 no.3
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• pp.243-253
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• 2006

The purpose of this study was to investigate dietitians' needs of teaching materials about nutrition education for school children in Kyonggi and Chungnam(including Daejeon) areas. This study was carried out using questionnaires via e-mail or in class to the subjects of 166 elementary school dietitians as 68 in Kyonggi and 98 in Chungnam. The number of small(less than 700 meals), medium(700-1400 meals) and large(over 1400 meals) schools based on served meals daily were 48, 62 and 56, respectively. The results are as follows: Frequency of nutrition education for students as well as for teachers was samely very low as 'once per two months' and the education used to perform during lunch time mostly. For preparing nutrition education they obtained informations from the internet(64.0%). The main topics of nutrition education they used to covered were 'et's eat breakfast', 'table manners', 'the relations of body and nutrients', 'food waste', 'foods and calorie', etc.. The largest limit of nutrition education practices faced by school dietitians were pointed out as 'lacks of teaching materials' and 'counseling techniques'. Most dietitians wanted CD or substantial teaching materials for the practices, and required their contents covering 'cooking', 'food and calories', 'let’s eat various foods', 'relations of body and nutrients', 'regular meal is important’ and etc.. Since we expect nutrition teachers to be realized soon, nutrition education/counseling is emphasized more as their duty. Even though school dietitians revealed poor self-confidence, they were positive to get improved by reeducation of nutrition counseling methods and skills. If easy and suitable education materials(CD type) are developed as good as the school dietitians desired, the materials could contribute much to better nutrition education/counseling practices at schools.

• Journal of the Korean Society of Clothing and Textiles
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• v.28 no.8
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• pp.1076-1087
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• 2004

The purpose of the study is to give new aesthetic values of black dress one of the important items in contemporary women＇s fashion. Through the work, to give the new aesthetic characteristics that women really needed can be found. This study was processed by fashion books and articles, literal material with fashion photos which were related fashion trend from 1920 to the present. The results are as follows: In early 20th century, the black dress, which had simple form pursuing function like little black dress. In the middle of the 20th century, elegance and minimalism was represented by black dress, expressed erotic images together with see-through fabrics. In the end of the 20th century, body conscious style of black dress expressed sensual images of women. Modem black dress has design characteristics of the form: simple, close, exposure type and of the materials: matte, transparent and dazzling etc. Simple type emphasizes feminine elegance, while close type and exposure type disclose woman body curve to express erotic images. Matte materials made black dress express feminine elegance while transparent materials and dazzling materials made black dress express erotic and sensual beauty. The aesthetic characteristics of black dress were as followings: Sensualism expresses sexual attractiveness of women-close type and exposure type black dress and see-through materials and dazzling materials made black dress. Simplicity of extreme decoration effects are expressed through black dress having temperate and simple form. Femineity expresses traditional femineity to emphasize chaste, modest and elegant women images-the black dress, which is made of simple form, velvet and satin materials. Modernism combines black colour, which is called modem colour, with simplicity and function factors and pursues simple form. Ascetic practice controls mental and physical desire of the individuals, simple form without decoration covering up woman body and box type silhouette of black dress. Therefore, the study on image of the black dress, which have made appearance at modern fashion, is thought to help develop fashion trends and design, through which modern women express themselves and their beauty.

• Korean Journal of Materials Research
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• v.20 no.9
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• pp.488-493
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• 2010

Geopolymer is a term covering a class of synthetic aluminosilicate materials with potential use in a number of areas, but mainly as a replacement for Portland cement. In this study, geopolymers with fly ash and meta kaolin were prepared using KOH as an alkali activator and water glass. The effect of water glass on the microstructures and the compressive strength of the geopolymer was investigated. As the amount of water glass increased, the dissolved inorganic binder particles in the geopolymers increased due to polymerization, resulting in a dense microstructure. The meta kaolin-based geopolymer showed a better extent of polymerization and densification than that of the fly ash-based geopolymer. XRD data also suggested that polymerization in meta kaolin-based geopolymers should be active resulting in the formation of an amorphous phase with an increasing amount of water glass. The compressive strength of the geopolymer was also dependent on the amount of water glass. The compressive strength of the geopolymers from both fly ash and meta kaolin increased with an increasing amount of water glass because water glass improved the extent of polymerization of the inorganic binder and resulted in a dense microstructure. However, the addition of water glass to the geopolymer did not seem to be effective for the improvement of compressive strength because the meta kaolin-based geopolymer mainly consisted of a clay component. For this reason, the fly ash-based geopolymer showed a higher value of compressive strength than the meta-kaolin geopolymer.

• Journal of the Korean Ceramic Society
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• v.51 no.3
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• pp.162-169
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• 2014

This paper introduces a microwave-assisted synthesis method to prepare hybrid $Bi_2Se_3-GR/TiO_2$ nanocomposites, which exhibit superior properties over single component materials. The as-prepared composites were characterized by XRD, UV-vis absorbance spectra, SEM,TEM, EDX, and BET analyses, revealing uniform covering of the graphene nanosheet with $Bi_2Se_3$ and $TiO_2$ nanocrystals. For visible light photocatalysis of Rh.B, a significant enhancement in the reaction rate was consequently observed with $Bi_2Se_3-GR/TiO_2$ composites. The degradation rate($k_{app}$) obtained for sonophotocatalysis was $6.8{\times}10^{-3}min^{-1}$, roughly 2.2 times better than that of VL photocatalysis under higher concentrations of Rh.B. The sonophotocatalysis was faster due to greater formation of reactive radicals as well as an increase of the active surface area of the $Bi_2Se_3-GR/TiO_2$ composites. The high activity is attributed to the synergetic effects of high charge mobility and red shift of the absorption edge of $Bi_2Se_3-GR/TiO_2$.

• Korean Journal of Materials Research
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• v.18 no.2
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• pp.73-76
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• 2008

[ $SF_6$ ] gas has been widely used as an insulating, cleaning and covering gas due to its outstanding insulating feature and because of its inert properties. However, the global warming potential of $SF_6$ gas is extremely high relative to typical global warming gases such as $CO_2$, CFCs, and $CH_4$. For these reasons, it is necessary to separate and collect waste $SF_6$ gas. In this study, the effects of a surfactant (Tween) on the formation rate of $SF_6$ gas hydrates were investigated. The $SF_6$ gas hydrate formation rate increased with the addition of Tween and showed a nearly 6.5 times faster hydrate formation rate with an addition of 0.2 wt.% Tween compared to an addition of pure water. This is believed to be due to the increased solubility of $SF_6$ gas with the addition of the surfactant. It was also found that $SF_6$ gas hydrate in the surfactant solution showed two-stage hydrate formation rates with a formation rate that increased rapidly in the 2nd stage.

• Korean Journal of Environment and Ecology
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• v.11 no.3
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• pp.270-276
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• 1997

The purpose of this study was to investigate the number of climbing plant species habitated in South Korea. Relationships between their distribution and environmental factors were surveyed. Research sites for vertical distribution were Mt.S rak, Mt.Kwangkyo, Mt. Eoudap and Mt. Chiri. The results of this study are as follows: The number of climbing plants habitated in South Korea was 267 species, 95 genera, 41 families. According as latitude lower, the number of climbing plant species increased. And most areas of Korean peninsula except for alpine regions and the northern part of North Korea seemed to be suited for the growth of climbing plants. The number of climbing plant species decreased with its altitude. And it is confirmed that their distributions were limited to the below of 1,500m sea level which was applicable to the area of Kira's warmth index above 45. The species of climbing plants changed with its plant community although at same altitude. The number of climbing plant species was different from the face of slope, and the species diversity became lower at south slope than that of north slope.

• Journal of Bio-Environment Control
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• v.25 no.2
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• pp.95-99
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• 2016

As the survey results of cultivation area, farmhouse, yield and income to clarify the effect of PO Film on Korean melon industry in Seongju region, the covering areas of PE film of Korea, Kyungsangbuk-do and Seongju-gun in 2014 were decreased 91.5%, 94.9% and 95.2% as to 2010. In contrary, the covering areas of PO film of Korea, Kyungsangbuk-do and Seongju-gun in 2014 were increased 342.5%, 500% and 825% as to 2010. The cultivation area and farmhouse in 2015 were decreased 8.8% and 11.9% than those in 2010. The yield and production in 2015 were 38.2% and 25.9% increased han those in 2010. The gross and net income in 2015 were 1.3 and 2.7 times increased than those in 2010. Finally, to change as PO film, the productivity will be increased. And cleaning work and noxious materials discharge will be decreased.

• Journal of the Korean Society of Costume
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• v.61 no.5
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• pp.123-138
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• 2011

This study examined how Chipogwan[緇布冠] with such a long history has been changed in China and Korea. With regard to the name, material, use and form of Chipogwan, the results of this study is summarized as follows. Chipogwan was mentioned continuously in ancient books of ceremonies and literature from the Tang dynasty [唐代], but from the Song dynasty [宋代] new name Chigwan [緇冠: a black hat] appeared besides Chipogwan. The two names were transmitted to Joseon dynasty [朝鮮] and used together until the mid Joseon dynasty, but from the 18th-19th centuries, Chipogwan was adopted according to ancient ceremonies and this name has been used continuously until today. The change of the name reflects the change of the material. Ancient Chipogwan was made of hemp [布] but when the term Chigwan appeared in the Song dynasty it was made of paper and Sa [紗: a 2-end simple gauze]. As other materials were added to hemp, po (布) was omitted from Chipogwan. As to the use of Chipogwan, it was a coronet used in purification ceremonies [齋冠] in ancient times. Then, it was used as Chogagwan [初加冠: a first hat putting on] in coming-of-age ceremonies [冠禮] from Zhou dynasty (周). During the Song and Joseon dynasty, Chipogwan was used in coming-of-age ceremonies as well as in daily life. As to the form, Chipogwan in ancient books of rites and the Song dynasty was a small coronet covering the topknot. In the Joseon dynasty, the form of Song dynasty was followed until the mid period, and then after the mid $18^{th}$ century, another form was proposed according ancient books of rites and an independent form of ceremonial coronet appeared that covered the entire head rather than covering only the topknot.

• Wind and Structures
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• v.26 no.2
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• pp.75-87
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• 2018

A large number of low-rise buildings experienced serious roof covering failures under strong wind while few suffered structural damage. Clay and concrete tiles are two main kinds of roof covering. For the tile roof system, few researches were carried out based on Finite Element (FE) analysis due to the difficulty in the simulation of the interface between the tiles and the roof sheathing (the bonding materials, foam or mortar). In this paper, the FE analysis of a single clay or concrete tile with foam-set or mortar-set were built with the interface simulated by the equivalent nonlinear springs based on the mechanical uplift and displacement tests, and they were expanded into the whole roof. A detailed wind tunnel test was carried out at Tongji University to acquire the wind loads on these two kinds of roof tiles, and then the test data were fed into the FE analysis. For the purpose of validation and calibration, the results of FE analysis were compared with the full-scale performance ofthe tile roofs under simulated strong wind impact through one-of-a-kind Wall of Wind (WoW) apparatus at Florida International University. The results are consistent with the WoW test that the roof of concrete tiles with mortar-set provided the highest resistance, and the material defects or improper construction practices are the key factors to induce the roof tiles' failure. Meanwhile, the staggered setting of concrete tiles would help develop an interlocking mechanism between the tiles and increase their resistance.