• 태양에너지
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• 제9권1호
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• pp.53-61
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• 1989

In the present investigation, experiments on the melting of a phase change material were performed to research heat transfer phenomena generated by means of conduction and natural convection in the vertical tube at inward melting. The phase change material used in the experiments is 99 percent pure n-Docosane paraffin which is measured melting temperature of $42.5^{\circ}C$, latent heat of 37.5 cal/g, heat conductivity of $0.1505W/m^{\circ}C$. Experiments were performed both in the no-subcooling which is initiating it at melting temperature of phase change material, and in the subcooling which means to initiate it under melting temperature of phase change material, in order to compare and investigate the horizontal temperature history, vertical temperature history, ratio of melting and melted mass, figure of the melting front in the vertical tube. In the experimental results, heat transfer from tube wall to phase change material were due to conduction at early stage and due to natural convection with the passage of time, and then occurred melting downward from surface by volumetric expansion. Natural convection affects temperature distribution in the tube, ratio of melting and melted mass, figure of the melting front and then progress rapidly in case of nosubcooling compared to subcooling.

• 한국의류학회지
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• 제23권6호
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• pp.788-799
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• 1999

This study was performed to investigate the effect of mordants on the dyeability colorfastness to light and to laundering and biological properties of mordanted and natural-dyed cotton and silk substrates. Natural red dyes were extracted from Caesalpinia Sappan L. (Sappan wood) and Rubia Akane Nakai (Madder) by boil water Five different compounds of Al, Cr, Cu, Fe and Sn were used as mordanting agents. The result of this study are sumarized as follows ; 1. In the of the fabrics mordanted and dyed with sappan wood K/S value increases and λmax shifts to the longer wavelength as mordant concentration increases. Color of the fabrics dyed with sappan wood and madder change to redder bluer and lighter after mordanting. 2. As the number of repetition of dyeing-mordnating process increase the color of the dyed fabrics tend to be redder bluer and darker. Mordanted dyes with Al and Sn make chroma increase. The quantity of mordant absorbed in the silk fabric increase as mordant concentration increase. More Fe is absorbed in silk than Cr is. 3. After being exposed to light the fabrics dyed with sappan wood and madder change to less red Fe and Cu mordanting yeild better colorfastness to light than others does. Natural-dyed fabrics exposed to light tend to be faded and whitened in CIELAB chromaticity co-ordinates. So we might trace back the original color of ancient faded fabrics by changes in color of natural dyes. 4. After washing the colors of natural dyes change to more blue, Fe and Cu mordanting give better colorfastness to wash than others do. 5. The soil-burial cotton is more susceptible to mildew and rot than the silk is. Antimicrobial activity of the natural-dyed cotton can be enhanced by Cu and silk can be enhanced by Cu and Cr mordanting respectively.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2003년도 추계학술대회 논문집
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• pp.152-157
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• 2003

Natural frequencies of the transνerse vibration of beams with step change in cross-section are obtained by using the asymptotic closed form solution. This closed form solution is found by using WKB method under the assumption of slowly varying properties, such as mass, cross-section, tension etc., along the beam length. However, this solution is found to be still very accurate even in the case of large variation in cross-section and tension. Therefore, this result can be easily applied to many engineering problems.

• 복식문화연구
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• 제11권3호
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• pp.431-440
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• 2003

The purpose of this study is to investigate the feasibility of applying the chitosan for a natural mordant. The chitosan, a natural chelate macromolecule, is acquired from the crustacean. Investigation was focused on the change of the dyeability according to the chitosan treatment based on the Caesalpinia sappan and the color change of the dyed fabric according to the application of heavy metal mordant. The change of air permeability of the fabric with the dyeing condition was also investigated systematically. The effect of dyeing with/without mordant on the air permeability of the fabric after the chitosan treatment. It seems that the increase in the dye-uptake is attributable to the fact that chitosan forms a complex with the Caesalpinia sappan and Al during mordant dyeing of cotton fabric. For nylon fabric, the darkest color was achieved on the occasion of non-mordant dyeing of the fabric. The mordant treatment or chitosan treatment, however, reduced the dyeability. While the dyed nylon fabric could maintain the same air permeability as the grey nylon fabric, the cotton fabric lowered the air permeability after dyeing.

• 대한토목학회논문집
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• 제33권2호
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• pp.801-810
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• 2013

본 연구는 기후변화로 인하여 심각해져가고 있는 자연재해에 보다 효율적인 대응방안을 마련하기 위한 이론적 토대를 확립하고자 도시계획분야의 지속가능성 개념을 재정립하였다. 과거 지속가능성 개념에 대한 고찰과 최근 미국 방재학계의 동향을 분석하여 마련한 새로운 지속가능개발은 기존 환경분야 주요 목표인 환경보호와 더불어 이상기후로부터 도시 사회 안전성 확보가 포함되어야 함을 인식하였다. 그리고 도시 사회 안전성 확보는 저탄소녹색도시 관련요소와의 연계 속에서 이뤄져야 함을 강조하였다. 또한 환경, 경제, 사회분야의 목표를 동시에 추구함으로써 야기되는 갈등을 인식하고 대형화된 자연재해에 효과적으로 대응하기 위하여 기존 공학 시설중심의 구조적 방재대책과 더불어 비구조적 대책의 적극적 도입 필요성을 제시하였다. 본 연구에서 제시한 이론적 틀을 바탕으로 도시계획분야의 향후 연구는 갈등 조정 중재를 위한 새로운 제도적 틀 마련과 함께 APFM(the Associated Programme on Flood Management)에서 제시한 '노출(Exposure)'과 '취약성(Vulnerability)' 요인을 바탕으로 환경보호와 안전성 확보는 물론 관련 갈등해소에 기여할 수 있는 세부 요소 목표설정, 구체적 관련 기술개발 등에 노력해야 할 것으로 판단된다.

• 한국농공학회지
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• 제56권2호
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• pp.2-15
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• 2014

• Computers and Concrete
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• 제17권2호
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• pp.241-253
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• 2016

Depending on the researcher, the effect of prestressing on the natural frequency of a PSC (prestressed concrete) structure appear to have been interpreted differently. Most laboratory tests on PSC beams available showed that the natural frequency is increased appreciably by prestressing. On the other hand, some other references based on field experience argued that the dynamic response of a PSC structure does not change regardless of the prestressing applied. Therefore, the deduced conclusions are inconsistent. Because an experiment with and without prestressing is a difficult task on a full size PSC bridge, the change in natural frequency of a PSC bridge due to prestressing may not be examined through field measurements. The study examined analytically the effects of prestressing on the natural frequency of PSC bridges. A finite element program for an undamped dynamic motion of a beam-tendon system was developed with additional geometric stiffness. The analytical results confirm that a key parameter in changing the natural frequency due to prestressing is the relative ratio of prestressing to the total weight of the structure rather than the prestressing itself.

• 한국의상디자인학회지
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• 제4권3호
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• pp.9-15
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• 2002

Compared with synthetic dyes, natural dyes have inferior colorfastness as a result of the exposure of the material to any environment that may be encountered during the processing, testing, storage, display or use of the dyed materials. Especially, colors on fabrics fade excessively after washing. Therefore, it is problem to infer the historic textiles with natural-dyed fabrics. The object of this study is to analyse the factors affected to colorfastness and color change during washing. In experimental, fifteen natural dyes were dyed by the Korean traditional dyeing methods onto natural fiber fabrics: cotton, silk, ramie, and flex. Total 49 dyed fabrics in combination with dyes and fibers were used for the specimen. The Launder-Ometer was used for evaluating the effects of exposure to repetitive washing from 1 to 20 washing cycles (KS K 0430). Color difference(ΔE) in the CIEL＊A＊B＊ color-order system were determined by spectrophotometer at 100 bserver. Washing caused significant changes in the color of natural-dyed fabrics. The degree and nature of color changes on the fabrics were dependent on the combination of fiber and the dye type used. The groups of violet(Lithospermum erythrorhizon Sieb.et Zucc) and black color(Ailanthus altissima Swingle, Phus trichocarpa Miq) yielded excellent colorfastness to repetitive washing. The group of indigo blue color(Polygonum tinctorium Lour.) was also very resistant to color change in washing except silk. Whereas the dye groups of Red, Yellow, Orange, Brown colors indicated greatest changes in color, particularly Carthamus tinctorius L.

• 한국제4기학회지
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• 제17권2호
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• pp.47-54
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• 2003

Climate of Mongolia is a driven force on natural conditions as well as socio-economic development of the country. Due to the precariousness of climate conditions and traditional economic structure, natural disasters, specially disasters of meteorological and hydrological origin, have substantial effect upon the natural resources and socio-economic sectors of Mongolia. Mongolia's climate is characterized by high variability of weather parameters, and high frequency and magnitude of extreme climate and weather events. During the last few decades, climate of the country is changing significantly under the global warning. The annual mean air temperature for the whole territory of the country has increased by $1.56^{\circ}C$ during the last 60 years,. The winter temperature has increased by $1.56^{\circ}C$. These changes in temperature are spatially variable: winter warming is more pronounced in the high mountains and wide valleys between the mountains, and less so in the steppe and Gobi regions. There is a slight trend of increased precipitation during the last 60 years. The average precipitation rate is increased during 1940-1998 by 6%. This trend is not seasonally consistent: while summer precipitation increased by 11 %, spring precipitation decreased by 17. The climate change studies in Mongolia show that climate change will have a significant impact on natural resources such as water resources, natural rangeland, land use, snow cover, permafrost as well as major economic activities of arable farming, livestock, and society (i.e. human health, living standards, etc.) of Mongolia. Therefore, in new century, sustainable development of the country is defined by mitigating and adaptation policies of climate change. The objective of the presentation is to contribute one's idea in the how to reflect the changes in climate system and weather extreme events in the country's sustainable development concept.

• Journal of Forest and Environmental Science
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• 제39권2호
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• pp.105-117
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• 2023

Climate change and invasive alien plant species (IAPs) are having a significant impact on mountain ecosystems. The combination of climate change and socio-economic development is exacerbating the invasion of IAPs, which are a major threat to biodiversity loss and ecosystem functioning. Species distribution modelling has become an important tool in predicting the invasion or suitability probability under climate change based on occurrence data and environmental variables. MaxEnt modelling was applied to predict the current suitable distribution of most noxious weed A. adenophora (Spreng) R. King and H. Robinson and analysed the changes in distribution with the use of current (year 2000) environmental variables and future (year 2050) climatic scenarios consisting of 3 representative concentration pathways (RCP 2.6, RCP 4.5 and RCP 8.5) in Bhutan. Species occurrence data was collected from the region of interest along the road side using GPS handset. The model performance of both current and future climatic scenario was moderate in performance with mean temperature of wettest quarter being the most important variable that contributed in model fit. The study shows that current climatic condition favours the A. adenophora for its invasion and RCP 2.6 climatic scenario would promote aggression of invasion as compared to RCP 4.5 and RCP 8.5 climatic scenarios. This can lead to characterization of the species as preferring moderate change in climatic conditions to be invasive, while extreme conditions can inhibit its invasiveness. This study can serve as reference point for the conservation and management strategies in control of this species and further research.