• Journal of the Korean Society of Environmental Restoration Technology
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• v.14 no.6
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• pp.1-15
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• 2011

We recently witnessed increasingly more natural disturbances on forested land. On the other hand, only limited number of nursery grown tree species are available for restoration projects. At the same time, so little on the disturbance resistance of species has been studied that a selection of right species for right site condition becomes very difficult. This study is a compilation of the site specificities and disturbance resistance of each species native to South Korea. Each species was surveyed for 11 items related to site specificities, and 12 items related to disturbance resistance including the resistance to snow damage. This study was conducted for 161 tree species from 44 families : 21 evergreen conifer species, 2 deciduous conifer species, 18 evergreen broad-leaved species, 118 deciduous broad-leaved species, and 2 monocotyledon species. This study suggests that native species in South Korea show resistance to all types of natural disturbances except drought.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.46 no.5
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• pp.395-400
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• 2001

We investigated the variations of the flowering response to daylength in Perilla crop (var. frutescens). Seventeen accessions of Perilla crop and one accession of weedy type of var. crispa from China, Korea and Japan were cultivated under three daylength conditions, i.e., short-days, natural daylength and long-days. Most accessions of Perilla crop from China, Korea and Japan were divided into three types, early maturing type, intermediate maturing type and late maturing type by their natural flowering habit. In most of the accessions used, the flowering habit was significantly accelerated by short-day conditions and was delayed by long-day conditions. All the accessions of Perilla crops flowered within 57 days under the 10 hrs light treatment, whereas they did not flower at all even at 170 days after sowing under the 16 hrs light treatment. Thus, this finding suggested that there is a relationship between the types of flowering response to daylength and the geographical distribution which determines the planting season in traditional cultivation practices of Perilla crops. Positive correlation was observed between days to flowering and plant height or internode number in both the short-day and natural daylength conditions. Whereas, correlation was negative between days to flowering and inflorescence length or floret number in natural daylength condition, but it was positive in the short-day condition. Therefore, the daylength condition is considered as the most important environmental factor for flowering habit and morphological characters of Perilla crops. Flowering habit is considered as an important key character for the study of geographical differentiation of Perilla crop in East Asia.

• Journal of Engineering Education Research
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• v.14 no.4
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• pp.20-28
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• 2011

Writing education for the students who major in natural sciences and engineering is concentrated on just writing in liberal education. So, this article study the condition and practical solution of writing education with a focus on natural sciences and engineering. This article researches the condition of writing in these majors of Seoul National University, Massachusetts Institute of Technology and Stanford University. As a result, students keenly feel the necessity of writing in this major, but SNU does not offer such courses and few teachers that could teach it. To solve this, we propose that writing teachers of liberal education give feedback on the reports of the capstone research subject 3 or 4 times, which corresponds to 1 credit. This solution would be applicable to most universities in practice, though it is not final method.

• Proceedings of the Korea Institute of Fire Science and Engineering Conference
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• 1997.11a
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• pp.146-153
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• 1997

An experimental study was performed of natural-convection downward smolder spread across a sawdust bed peripherally enclosed with an insulating container, to examine the effect of the open- ing condition at the top end on downward smolder spread. Experiments were conducted by using relatively coarse sawdust and 25-cm-long cylindrical container The variations of temperature profiles along the bed axis with time were determined far different opening conditions and were com-pared with those in smolder spread from open top to open bottom. It was shown that the smolder zone initiated from open top toward closed bottom penetrates the bed with keeping high peak temperature like the case of open top to open bottom spread, although mean spread rate is smaller. This indicates that the downward smolder zone can be sustained stably if sufficient air or oxygen Is supplied from the back of it by natural convection even if upward draft entering from the bottom of the bed is absent. When the top end was partially closed by mounting a cover after stable smolder spread had begun from open top toward open bottom, the temperature at the peak decreased more than 200 K and the smolder zone became to spread with thickening residue. In this case, the shape of temperature profiles continuously changed or decayed until end-effect at the open bottom end enhanced the reaction. The temperature at the shrunk peak, free from the end-effect, was almost identical with the temperature at the exothermic oxidative-degradation zone in smolder spread from open top to open bottom. from these results, it can be inferred for natural-convection downward smolder spread that the oxidation reaction of the char is very sensitive to the oxygen supply by natural convection in the space above the smolder zone, and that the top end opening condition strongly alters the completeness of reactions, structure, and behavior of the smolder zone.

• 한국생물공학회:학술대회논문집
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• 2000.04a
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• pp.247-250
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• 2000

Extracellular polysaccharide was produced by Pseudomonas elodea ATCC 31461 under aerobic condition. Nitrogen sources in medium affected cell growth and production of exopolymer. Ammonium nitrate limitation was found to be essential for higher production of exopolymer. Conversion rate of exopolymer from glucose under ammonium nitrate limitation was about 5 times higher than with ammonium nitrate.

• Geomechanics and Engineering
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• v.12 no.6
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• pp.949-963
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• 2017

The main purpose of the current study is to develop the new coefficients for consideration of soil-structure interaction effects to find the elevated tank natural period. Most of the recommended relations to find the natural period just assumed the fixed base condition of elevated tank systems and the soil effects on the natural period are neglected. Two different analytical systems considering soil-structure- fluid interaction effects are recommended in the current study. Achieved results of natural impulsive and convective period, concluded from mentioned models are compared with the results of a numerical model. Two different sets of new coefficients for impulsive and convective periods are developed. The values of the developed coefficients directly depend to soil stiffness values. Additional results show that the soil stiffness not only has significant effects on natural period but also it is effective on liquid sloshing wave height. Both frequency content and soil stiffness have significant effects on the values of liquid wave height.

• Proceedings of the Korean Society of Life Science Conference
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• 2006.09a
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• pp.45.1-45.1
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• 2006

• Transactions of the Korean Society of Automotive Engineers
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• v.3 no.6
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• pp.112-122
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• 1995

As an alternative fuel producing less exhaust emissions, natural gas is of interest for use both in SI and CI engines. The potential of natural gas fuelled dual-fuel engine is considered high enough. However, much effort has to be made so that gaseous fuel is used efficiently with simultaneous minimum use of pilot oil. Hence, a simplified three-dimensional model, using a finite volume method in cylindrical coordinates, has been developed to facilitate an understanding of the dual-fuel combustion phenomena and to predict the complex interactions between the pilot distillate and natural gas. The computer model was calibrated by comparing it with the experimental results obtained from diesel engine like combustion bomb tests. In the pre-mixed natural gas combustion, the fuel burning was highly reliant on the injection condition and subsequent burning nature of the pilot distillate.

• Elastomers and Composites
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• v.51 no.2
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• pp.106-112
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• 2016

Maleimidopropyltriethoxysilane grafted natural rubber (MISNR) was prepared by reaction of maleic anhydride grafted natural rubber and 3-aminopropyl triethoxysilane. MISNR was used as the compatibilizer of natural rubber/silica composites. The composites were prepared by two-step mixing procedures. The final mixtures were cured with optimum cure condition, which was established by a rheometer. Effects of the amounts of compatibilizer in the composites on the cure characteristics, morphology, thermal stability, and physical and mechanical behaviors were investigated. The composites having MISNR had shown cure characteristics and physical and mechanical properties superior to those without MISNR. Silica particles in the former appeared to be more uniform and reduced in size compared with the latter. The effects of the types of silica were also evaluated.

• Bulletin of the Korean Chemical Society
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• v.33 no.1
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• pp.76-82
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• 2012

A novel and efficient tetrahydrofuranyl ring opening method was developed using the highly reactive TFAT reagent in the presence of an acid scavenger, 2,6-di-tert-butyl-4-methylpyridine. Various acid sensitive groups are compatible with the reaction condition, making it generally applicable to many tetrahydrofuranyl steroids. Moreover, it is a synthetic equivalent of 'Marker degradation' affording an efficient synthesis of C17-OH rockogenin acetate.