• Transactions of the Korean Society of Mechanical Engineers B
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• v.36 no.3
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• pp.309-314
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• 2012

Flame flickering occurs mainly because of the buoyancy force for pool fires under ambient air. The cup-burner flame was used for experimental investigation of the effect of the oxidizer velocity on the gravitational instability. The results showed that the flickering frequency decreased with increasing oxidizer velocity. The frequency-buoyancy relation with nondimensional variables coincided with that of the buoyant flume and pool fires when the characteristic velocity was defined as the difference between the fuel and oxidizer velocities, which implies that the origin of the gravitational instability is the Kelvin-Helmholtz instability in the shear layer. The effect of the oxidizer composition on the instability was also examined through nitrogen dilution in the oxidizer stream. As the concentration of inert gas increased, the length of the blue flame increased and lift-off behavior was observed. The oscillation frequency was independent of the dilution ratio, but was related to the local flame structure.

• Proceedings of the Plant Resources Society of Korea Conference
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• 2022.09a
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• pp.52-52
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• 2022

제주도 서귀포시와 경북 안동시에서 사마풀속(Murdannia Royle)에 속하는 미기록 외래식물인 Murdannia nudiflora (L.) Brenan를 발견하여 보고하고자 한다. Murdannia nudiflora는 열대 아시아 원산으로 아프리카, 아메리카 대륙뿐만 아니라 우리나라와 가까운 일본에도 도입되어 있다. 종소명인 'nudiflora'는 본종의 조락하는 소포엽의 특징을 지칭하는 것으로 추정되며, M. nudiflora는 소포엽 외에 국내 자생하고 있는 사마귀풀[M. keisak (Hassk.) Hand.-Mazz.]과 뿌리, 꽃, 열매 및 종자의 외부형태로 쉽게 구분할 수 있다. M. nudiflora는 사마귀풀과 달리 뿌리줄기가 없고, 말단 혹은 액생하는 화서에 여러 개의 꽃이 피며, 꽃은 수술 2개, 헛수술 2-4개를 가지고, 열매는 자실 당 2개의 종자를 가지며, 종자는 작은 구멍이 있는 망상형 표면을 가진다. M. nudiflora는 닭의장풀과(Commelinaceae)에 속하는 분류군 중에서도 병해충을 유발하여 작물의 생산성을 감소시키는 잡초로 악명이 높으며, 주로 목화, 벼, 참깨 등과 같이 주요 작물이 재배되는 경작지에서 발견되는 것으로 알려져 있다. 본 종의 발견지들은 모두 해당 작물을 재배했던 것으로 추정되는 경작지로 M. nudiflora는 수입된 재배종 종자와 섞여 비의도적으로 도입된 것으로 보인다. 본 연구에서는 M. nudiflora의 화상자료 및 형태적 기재와 함께 국내 근연 분류군과 구별할 수 있는 검색표를 제시하고자 한다.

• Fire Science and Engineering
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• v.19 no.3 s.59
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• pp.58-63
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• 2005

Experimental measurements of flames and the product properties were performed for small kerosene pool fires. which is widely used as a fire source of laboratory scale experiments with scaling modeling. The flame length and flickering frequency were investigated for the flame structures, and compared with the theory. Three measurement methods were introduced to clarify the smoke characteristics, i.e. various gas concentrations, smoke density and thermophoretic sampling with transmission electron microscopy (TEM). The yield of carbon dioxide and the consumption of oxygen were proportional to the heat release rate of pool fires, but there is no trend on carbon monoxide emission. Smoke density of turbulent flames was exponentially increased with the heat release rate. The morphology of the soot particle was investigated to address the degree of soot maturing. The results show that the similar smoke morphology between an inverse jet flame and a pool fire exists despite of different combustion controlling mechanisms.

• School Mathematics
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• v.10 no.2
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• pp.181-197
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• 2008

Bertrand's Paradox is known as a paradox because it produces different solutions when we apply different method. This essay analyzed diverse problem solving methods which result from no clear presenting of 'random chord'. The essay also tried to discover the difference between the mathematical calculation of three problem solvings and physical experiment in the real world. In the process for this, whether geometric statistic teaching related to measurement and integral calculus which is the basic concept of integral geometry is appropriate factor in current education curriculum based on Laplace's classical perspective was prudently discussed with its status.

• Proceedings of the Korean Society of Computer Information Conference
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• 2020.01a
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• pp.243-244
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• 2020

본 논문에서는 SIM(Soft Island Model)을 통해 소집단 정보를 이동시키기 위한 KSDE라고 하는 수많은 전략을 제안한다. 먼저, 전체 모집단은 k- 평균 군집 알고리즘에 의해 k 개의 하위 모집단으로 분리된다. 둘째, 소집단에 돌연변이 조작을 수행하기 위해 전략 풀에서 돌연변이 전략을 무작위로 선택한다. 마지막으로, 이 알고리즘의 모집단 다양성을 개선하기 위해 하위 집단 정보가 SIM을 통해 마이그레이션 된다.

• Microbiology and Biotechnology Letters
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• v.42 no.1
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• pp.51-57
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• 2014

In this study, the antioxidative effects and component analysis of Polygonum aviculare (P. aviculare) extracts were investigated. The ethyl acetate and the aglycone fraction from P. aviculare extracts were more active than (+)-${\alpha}$-tocopherol and $\small{L}$-ascorbic acid, which are known as strong antioxidants for their antioxidative activity by the DPPH method and chemiluminescence assay. The cellular protective effects of fractions of P. aviculare on the rose-bengal sensitized photohemolysis of human erythrocytes, increased in a concentration dependent manner ($1-10{\mu}l$). In particular, the ethyl acetate fraction at a concentration of $10{\mu}l$ showed the most prominent protective effect among all the extracts (${\tau}_{50}$, 314.70 min). TLC and HPLC chromatogram of the ethyl acetate fraction of P. aviculare extracts revealed 3 main bands (PA8, PA5, PA6) and peaks (peak 1, peak 2, peak 3), which were identified as myricetin-3-O-rhamnoside (myricitrin, PA8, peak 1), quercetin-3-${\alpha}$-rhamnoside (quercitrin, PA6, peak 3) by LC/ESI-MS/MS and $^1H$-NMR respectively. These results indicate that fractions from P. aviculare could be applicable to new functional cosmetics as antioxidants.

• The Journal of the Korea Contents Association
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• v.16 no.2
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• pp.332-343
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• 2016

With the advance of digital technology, new methods which acquire color information and combine it with various contents are emerging. Color has some effect on emotion while it gives some information as component of an image. In addition, change in emotion and sensation from color stimulus makes some change in cognition. This research investigate the effect of color overlay on cognition depending on emotional state. With this goal, subjects consisting of 10 men and 10 women solved some problems with color overlay of red, orange, and green after watching short video clips which intend to induce target emotion. Experimental results show that red color overlay under positive emotion significantly reduces the average score of solving problems, while green overlay under negative emotion significantly increases it. It is also analyzed that there is not statistically significant difference in cognitive function with color overlay while it is significantly better under positive emotion than negative emotion without color overlay.

• Communications of Mathematical Education
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• v.33 no.3
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• pp.377-394
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• 2019

The purpose of this study is to scrutinize the characteristics of a teacher's discursive competence on the basis of mathematical competencies. For this purpose, we observed all semester-long classes of a middle school teacher, who changed her own teaching methods for the last 20 years, collected video clips on them, and analyzed classroom discourse. Data analysis shows that in problem solving competency, she helped students focus on mathematically important components for problem understanding, and in reasoning competency, there was a discursive competence which articulated thinking processes for understanding the needs of mathematical justification. And in creativity and confluence competency, there was a discursive competence which developed class discussions by sharing peers' problem solving methods and encouraging students to apply alternative problem solving methods, whereas in communication competency, there was a discursive competency which explored mathematical relationships through the need for multiple mathematical representations and discussions about their differences. These results can provide concrete directions to developing curricula for future teacher education by suggesting ideas about how to combine practices with PCK needed for mathematics teaching.

• Journal of Life Science
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• v.33 no.5
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• pp.406-413
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• 2023

In this study, the various physiological and anti-inflammatory activities of Sanguisorba officinalis L. roots (SR) were assessed for potential use as functional cosmetic materials. As a result of measuring electron-donating abilities to determine the antioxidant ability of SR extract, activity increased as the concentration increased, showing an excellent antioxidant capacity of 93.8% at a 1,000 ㎍/ml concentration. Further, the antioxidant power of SR extract, which was determined using an ABTS⁺ assay measurement, was more than 99% at concentrations of 50 ㎍/ml or more, while the tyrosinase inhibition rate was 37.7% at the highest concentration of 1,000 ㎍/ml. Consequently, the elastase and collagenase inhibition of SR extract measured 84.9% and 90.3%, respectively, at a 1,000-㎍/ml concentration. As a result of confirming the survival rate of Raw 264.7 cells, the cell survival rate was determined to be 80% or more below a 100 ㎍/ml concentration, and subsequent cell-related experiments were conducted at concentrations below 100 ㎍/ml. Furthermore, after applying a NO assay to identify anti-inflammatory activity, it was confirmed that SR extract had an inhibitory rate of 50.8% at a concentration of 500 ㎍/ml, and it was excellent at suppressing the inflammatory expression. As a result of verifying protein expression by treating SR extract in Raw 264.7 cells, it was confirmed that expression was inhibited concentrated in all factors. Therefore, it is judged that SR can be used as a functional cosmetic material with antioxidant, whitening, and wrinkle-improving physiological effects and anti-inflammatory activities.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.6 no.2
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• pp.21-26
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• 2003

The purpose of this study was to investigate morphological characteristics of 153 wild grown Poa pratensis collected from various areas of Korea and to see correlation among morphological characteristics and visual rating. Morphological characteristics such as plant height, leaf length, leaf width were measured. The collected Poa pratensis plants showed various morphological differences. The plant height of Poa pratensis ranged from 4.5 to 40.0cm. Poa pratensis leaf length ranged 3.0 to 30.2cm and leaf width ranged 1.0 to 5.0mm. The mean values of Poa pratensis height, leaf length and leaf width were 18.2cm, 13.1cm and 2.7mm respectively. The Poa pratensis plots were also visually rated 1 to 9 scale throughout the growing season for their overall characteristics as turfgrass. The height, leaf length, leaf width and visual rating had significant positive correlations. Especially the height and leaf length had a highly significant positive(r=0.74) correlation.