• Proceedings of the Korea Water Resources Association Conference
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• 2006.05a
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• pp.613-617
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• 2006

Bed material in natural streams is affected by geological characteristics of upstream and acting focre by flow of stream. Acting force in streams are also affected by bed slope and discharge of streams. Yamamoto(1994) suggested that channel reaches with similar slope share similar characteristics values in representative bed material size, tractive force, channel width and depth. He also suggested that main factors dominating channel characteristics are mean annual discharge, epresentative bed material size and bed slope. Bed material shows physical and ecological characteristics of channels. In this research, characteristics of bed material in natural or close to natural streams were studied and compared with Janpanese stream data. In the result, characteristics of gravel and sand material can be presented in the term of non-dimensional tractive force, bed slope and bed material size.

• Textile Coloration and Finishing
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• v.19 no.6
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• pp.12-20
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• 2007

Four kinds of natural dying solutions (natural colorant extracts)were obtained by extraction from sappan wood, black tea, peony, and clove using water as extracting solvent at $90^{\circ}C$ for 90 min with liquor ratio (solid natural colorant material/solvent water, weight ratio) of 1/10. The dyeing, colour fastness and deodorizing properties of fabrics (cotton, silk, and wool fabrics) dyed with natural colorant extracts were compared. It was found that these properties were significantly dependent on the concentration of extracts, the structure of colorant, and the kind of fabrics. The K/S value of dyed cotton fabric increased in the order of peony < sappan wood < clove < black tea, however, the values of dyed silk and wool fabrics were in the order of peony < sappan wood < black tea < clove. Colour fastness (light, water, and perspiration fastness) was in the range of 3 - 5 grade except for sappan wood. The deodorizing performance of fabrics dyed with various natural colorants extracts was in the range of 56 - 99%. The deodorizing performance increased in the order of peony < black tea < sappan wood < clove. Especially, the deodorizing performance of all fabrics dyed with clove was found to be the highest at 98-99%.

• Textile Coloration and Finishing
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• v.19 no.1 s.92
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• pp.17-23
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• 2007

Dyeing properties using natural material named Sasa quelpaertensis Nakai were investigated under various conditions such as fabric type, pH, concentration, temperature, dyeing time and dipping count. Sasa quelpaertensis Nakai is a unique material in that it is raised only at Halla mountain in Jeju island and is known to have healing effect. Overall, wool fabrics were better than cotton fabrics in all aspects of the dyeing properties showing reddish yellow. For the fastness properties, robbins washing and perspiration fastness were excellent but lightfastness was poor as expected.

• Journal of Advanced Marine Engineering and Technology
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• v.30 no.6
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• pp.716-723
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• 2006

A meso-scale analysis method using the natural element method is proposed for the analysis of material damage of brittle microcracking solids. The microcracking is assumed to occur along Voronoi edges in the Voronoi diagram generated using the nodal points as the generators. The mechanical effect of microcracks is considered by controlling the material constants in the neighborhood of the micorcracks. The macro elastic moduli of isotropic solids containing a number of randomly distributed microcracks are calculated considering the effect of microcrack closure to demonstrate the validity of the proposed method.

• Journal of the Korean Institute of Landscape Architecture
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• v.28 no.4
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• pp.44-53
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• 2000

The purpose of this paper is to evaluate environmental friendliness for facilities of national park to improve naturalness of national park. We have evaluated environmental friendliness of the facilities in Chirisan national park in terms of resource conservation and environmental integration, which are consisted of 9 and 8 evaluation indicators, respectively. Environmental friendliness of the small facilities was not good due to not using locally obtained materials and natural material, and that of large and complex facilities was bad in the field of excessive damage during construction, inadequate maintenance, use of natural material, locally obtained material, environmental integration with surroundings. In evaluating environmental attributes, new facilities is better than the older ones. The small facilities appeared to be worse than those of the complex, and the large facilities are the worst in terms of environmental friendliness. In general, environmental friendliness turned out to be lower in the light of the facilities in the clustered area than those of the facilities of the other area. In the future, It is required that criteria for evaluating environmental friendliness of natural park facilities is established.

• BMB Reports
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• v.43 no.2
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• pp.133-139
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• 2010

We have performed analyses using ancient DNA extracted from 25 excavated human bones, estimating around the 1st century B.C. Ancient human bones were obtained from Nukdo Island, which is located off of the Korean peninsula of East Asia. We made concerted efforts to extract ancient DNA of high quality and to obtain reproducible PCR products, as this was a primary consideration for this extensive kind of undertaking. We performed PCR amplifications for several regions of the mitochondrial DNA, and could determine mitochondrial haplogroups for 21 ancient DNA samples. Genetic information from mitochondrial DNA belonged to super-haplogroup M, haplogroup D or its sub-haplogroups (D4 or D4b), which are distinctively found in East Asians, including Koreans or Japanese. The dendrogram and principal component analysis based on haplogroup frequencies revealed that the Nukdo population was close to those of the East Asians and clearly distinguished from populations shown in the other regions. Considering that Nukdo is geologically isolated in the southern part of the Korean peninsula and is a site of commercial importance with neighboring countries, these results may reflect genetic continuity for the habitation and migration of ethnic groups who had lived in a particular area in the past. Therefore, we suggest that phylogenetic analyses of ancient DNA have significant advantages for clarifying the origins and migrations of ethnic groups, or human races.

• Tribology and Lubricants
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• v.23 no.6
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• pp.318-322
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• 2007

The wear characteristics in supre-A dental material have been investigated. The wear tests were performed by using pin-on-disk wear tester at room temperature. Vickers hardness and fracture toughness measurement of dental materials were preformed. Microscopic observations on worn surfaces of specimens were conducted by SEM. The friction coefficient of supper-A material was investigated according to weight and slinging velocity. The hardness of supper-A material was a half of the enamel of natural teeth.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.04a
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• pp.501-507
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• 1997

Composite material has very excellent mechanical properties including tensile stress and specific strength. Especially impact loads may be expected in many of the engineering applications of it. The suitability of composite material for such applications is determined not only by the usual paramenters, but its impactor energy-absorbing properties. Composite material under impact load has poor mechanical behavior and so needs tailoring its structure. Genetic algorithms(GA) is probabilistic optimization technique by principle of natural genetics and natural selection and neural networks(NN) is useful for prediction operation on the basis of learned data. Therefore, This study presents optimization techniques on the basis of genetic algorithms and neural networks to minimum stiffness design of laminated composite material.

• Korean Journal of Mineralogy and Petrology
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• v.33 no.1
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• pp.65-71
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• 2020

Glass reference materials have been essentially used for precise geochemistry analytical techniques. In order to make up for the drawback of synthetic glass reference materials, which have the high uncertainty caused by the difference in composition of natural rocks, we introduce a glass geostandard using natural glass. The NK-B1G sample, which comes from the Baekdusan obsidian, is a natural glassy rock that contains only few crystals such as microlites or inclusions. We examined the feasibility of the sample as a reference material for microanalysis like EPMA or LA-ICPMS.

• Applied Chemistry for Engineering
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• v.5 no.6
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• pp.981-989
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• 1994

For the development of new material used bentonite in ceramic/organic material composite, ABS(acrylonitrile-butadiene-styrene) material was used as a matrix polymer and a series of bentonite was blended together. This bentonite, filler like talc or mica for plastic material, was used since natural bentonite(Ca type) is easily obtainable in Korea, Na-bentonite changed from natural bentonite by $Na_2CO_3$ based on the specified compositions, changes in the static and dynamic mechanical properties. It was discovered that the increased content of natural and Na- bentonite results in higher modulus with reduced impact strength. And Rockwell hardness was constant. And Na- bentonite filled polymer showed improvement in impact strength and lower in modulus as the natural bentonite filled polymer. The storage modulus(E') of Na- bentonite filled ABS resin was higher than that of Ca- bentonite filled ABS resin, while higher temperature, storage modulus(E') decreased. At higher frequency, tan ${\delta}$ peak was shifted at high temperature.