• Solar Energy
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• v.17 no.1
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• pp.93-102
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• 1997

The numerical study on the natural convection inside the L-shaped enclosure having a protrusion of which left wall is maintained at $T_c$. Right wall and part of the bottom and 2nd floor are at $T_h$ has been performed numerically for aspect ratio A=1, geometrically different cases and for $Ra=5{\times}10^5{\sim}2{\times}10^6$. As the L-shaped of the enclosure goes thicker horizontally and the smaller 2nd floor's length, the mean Nusselt number at the left cold wall becomes smaller for same Ra, and there is little influence of the increase of Ra on mean Nusselt number.

• Journal of Environmental Science International
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• v.20 no.12
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• pp.1521-1531
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• 2011

This study was carried out to determine the characteristics of the marine environment, including nutritional content, in order to clearly understand the outbreaks of Gonyaulax polygramma in the southern coastal areas in August, 2009. Samples were collected at 13 sites and water temperature and salinity were measured using a CTD. Field surveys were twice: the first between August 5-7, the second between August 22-24. The cell density of G. polygramma was 6,500-10,000 cells $ml^{-1}$ during the $1^{st}$ survey, whereas during the $2^{nd}$ survey the range of the cells was recorded from 8,000 to 12,500 cells $ml^{-1}$. Cochlodinium polykrikoides ranged from 0 to 105 cells $l^{-1}$ during the field survey. In water environments, the majority stations during the $1^{st}$ survey showed a nearly homogeneous water column below $1^{\circ}C$ in temperature, as well as similar profiles of salinity. However, the stratification between the surface and bottom was observed in the $2^{nd}$ survey. Regarding nutrients, Dissolved Inorganic Nitrogen (DIN) in the surface ranged from 0.144 to 0.236 mg $l^{-1}$ during the $1^{st}$ survey, and 0.082-0.228 mg $l^{-1}$ during the $2^{nd}$ survey. DIP (Dissolved Inorganic Phosphorus) did not show any difference in concentration between the $1^{st}$ and $2^{nd}$ survey. During August of 2009, the wind speed in the southern waters remained at around ${\leq}2\;m\;s^{-1}$ for about 60% of time, and there was very little precipitation during the month. Irradiance of ${\geq}10$ hr was shown in the late of August. It is thought that a low level of DIN and salinity play an important role as an essential factor for rapid growth, wide distribution and longer duration of red tide in G. polygramma.

• Proceedings of the Optical Society of Korea Conference
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• 1997.08a
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• pp.85-85
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• 1997

Czochralski 방법에 의해 육성된 Nd:YAG 단결정으로부터 CW mode의 1064nm laser를 발진시켰다. 육성된 단결정은 직경 50mm, 길이 120mm 이었으며, Nd 이온 농도는 O.2~0.9at% 이었다. 육성된 단결정 boule로 부터 결정학적 결함부위인 core 및 facet가 없는 양질의 단결정 부위를 Twyman-Green interferometer로 선빌하였다. 추출핀 부위는 절단, 가공, 연마공정 및 코팅 공정을 통해 직경 6.35mm, 길이 lOOmm의 laser rod를 제작하였다. 절단은 core drill, 또는 원통 연삭기를 사용하여 rod 형태로 가공하였으며, 상$\cdot$하면 polishing은 평행도 10", 직각도 5', 평활도 $\lambda$/10 수준까지 실험실에서 자체 가공하여 일반적인 laser 발진용 rod의 spec.을 만족시킬 수 있었다.

• Educational Technology International
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• v.17 no.1
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• pp.1-37
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• 2016

The purpose of this study was to develop a MOOC design model that would improve the current practice of MOOC development in Korea by specifying easy-to-use course development procedures and guiding strategies. Following Richey and Klein (2007)'s conceptual model development procedure, the first step was to perform critical review of relevant literature and observe typical MOOC development processes. As a result, the initial model was developed. The second step was to conduct the expert review with five educational technology and MOOC researchers to secure the internal validity of the model. Based on the experts' suggestions, the model was revised and once again reviewed by the same experts. This process resulted in the development of the 2^nd version of model. The third step was to carry out external validation research in order to test the effectiveness, efficiency, and usability of the model. A basic model may be confirmed or corrected based on examination of its results. Consequently, the model was elaborated as the final model. In the final model, 6 procedural phases and 9 specific steps were included. The six procedural phases are: Analysis (1st Iteration), Design, Development (Course Development), Implementation, Evaluation, and Analysis (2nd Iteration), a slight variation of ADDIE model. The specific steps include: 1) Goal Setting, 2) Environment Analysis, 3) Content Design, 4) Style Design, 5) Course Development, 6) Implementation Plan, 7) Course Implementation, 8) Summative Evaluation, and 9) Need Reflection. The study concluded with suggestions for further research and application of the MOOC design model.

• Journal of Ginseng Research
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• v.14 no.2
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• pp.157-161
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• 1990

We have been isolating various physiologically active substances from non-saponin fraction of Korean Red Ginseng. These are adenosine, pyre-glutamic acid, dencichine and acidic polysaccharide. Adenosine and pyre-glutamic acid are known to inhibit epinephrine-induced lipolysis in fat cells and stimulate the insulin-mediated lipogenesis. In addition to these actions, adenosine was found to inhibit both norepinephrine- and histamine-induced aorta constriction, and pyre·glutamic acid inhibits angiotensin-converting enzyme. Dencichine stimulated histamine-induced aorta constriction. Finally, acidic polysaccharide was found to inhibit both lipolytic and anorexigenic actions of Toxohormone-L. Based on these experimental results, I presented a briefreview on these compounds isolated from non-saponin fraction of Korea Red Ginseng.

• 한국도로학회:학술대회논문집
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• 2004.10a
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• pp.61-66
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• 2004

• Journal of Korean Society of Environmental Engineers
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• v.28 no.7
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• pp.776-781
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• 2006

Perchlorate ion($ClO_4^-$), which is present in the solid propellant for rocket, herbicide and some fertilizers. Perchlorate inhibits iodide uptake by the human thyroid gland. Impairment of thyroid function in expectant mothers may impact the fetus and result in effects including cerebral palsy, give rise to thyroid gland cancer. The US EPA(Environmental Protection Agency) adopted a reference dose(RfD) for perchlorate 0.0007 mg/kg-day, and this guidance lead to a Drinking Water Equivalent Level(DWEL) of 24.5 ${\mu}g/L$. The studies about perchlorate are actively performed in foreign countries, especially in USA but there is no study which surveyed the perchlorate contamination in Korea. Therefore, this study was done to investigate perchlorate contamination in Nak-dong river and tap water. The perchlorate was detected in Nakdong river and ranged from ND to 278.4 ${\mu}g/L$. The highest concentration was observed in Kumichon. The perchlorate concentration was decreased with the down stream of Nakdong river. The perchlorate concentration in tap water was varied with the cities and the concentration levels were $ND{\sim}34.1$ ppb. The highest perchlorate concentration was observed in DalsuGoo in Daegu and the similar concentration($9{\sim}11$ ${\mu}g/L$) was detected in most of the districts in Busan. The result of this study suggests that there is a perchlorate source near the Nakdong river and the urgent policy is needed to control perchlorate for the cities which are supplied from Nakdong river as for their tap water.

• Environmental Analysis Health and Toxicology
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• v.24 no.4
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• pp.341-350
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• 2009

This study involves a relationship between butyltins concentrations and histopathological changes of the digestive gland in the equilateral venus, Gomphina veneriformis exposed to TBTCl of 0.4, 0.6 and 0.8 ${\mu}g/L$ for 36 weeks. In the sediment, total butyltin (${\sum}BT$) concentration was detected ND~7.54 (0.4 ${\mu}g/L$), ND~9.76 (0.6 ${\mu}g/L$), 1.22~13.13 ${\mu}g/L$ (0.8 ${\mu}g/L$), respectively. Especially, TBT level in 0.8 ${\mu}g/L$ group was the highest for 36 weeks. In the soft tissue, total butyltin (${\sum}BT$) concentration of the exposure group was 10.14~12.75 (control), 479.29~1,286.56 (0.4 ${\mu}g/L$), 563.32~2,154.82 (0.6 ${\mu}g/L$) and 1,317.70~2,132.60 ${\mu}g/L$ (0.8 ${\mu}g/L$), respectively. Ratio of TBT to ${\sum}BT$ of the tissue of 0.8 ${\mu}g/L$ kept the lowest level for 36 weeks. The ${\sum}BT$ concentrations of sediment were correlated with ${\sum}BT$ concentrations in the tissue. In the exposure groups, necrosis and atrophy of columnar epithelial cell and collapse of epithelial layer in the digestive tubule. And there was a reduction in stain affinity of basophilic cell. Such histological degenerations was more severe in digestive tubule of 0.8 ${\mu}g/L$ group.

• Journal of the Korean Wood Science and Technology
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• v.37 no.6
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• pp.578-584
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• 2009

We investigated acid hydrolysis characteristics of yellow poplar woodmeal with concentrated sulfuric acid for high concentration of monosaccharides production. Woodmeal to 72% sulfuric acid ratio (w/w), $2^{nd}$ hydrolysis temperature and time were main variables for finding optimum reaction condition. Optimum woodmeal to 72% sulfuric acid ratio was 1 : 2.61 (w/w) and $2^{nd}$ hydrolysis temperature and time was $105^{\circ}C$ and 40 min as 44.8 g/L of glucose and 25.2 g/L of xylose in hydrolysis solution. In this acid hydrolysis solution, furfural, 5-HMF, low molecular weight phenolic compounds were identified. Furfural and 5-HMF concentration were increased as increasing $2^{nd}$ hydrolysis time. More than 40 min of $2^{nd}$ hydrolysis at $110^{\circ}C$, xylose concentration was decreased but glucose concentration was leveled out because xylose to furfural reaction was faster than xylan to xylose, but cellulose to glucose reaction was similar rate with glucose to 5-HMF at that $2^{nd}$ hydrolysis reaction condition.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.12 no.2
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• pp.94-101
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• 2007

Analysis of population structure of Oncorhynchus keta, the most abundant salmon in the East Sea of Korea, has not been much carried out despite its importance as a fishery resource in the North Pacific. Currently, molecular methods are being applied to stock identification and a method of using single nucleotide polymorphisms (SNPs) is getting more popular. In this study, we analyzed the 720 bp long sequence of the mtDNA COIII-ND3-ND4L region in order to examine genetic similarity-dissimilarity among the Korea chum salmons of each stream and their relationship with the Japan chum salmons. A total of 152 individuals were analyzed, 108 from 3 locations of Korea and 44 from 2 locations of japan, which resulted in as many as 29 different haplotypes. Pairwise $F_{ST}$ and AMOVA tests of the populations show that there is no significant population-level genetic difference among the chum salmons analyzed ($F_{ST}<0.07$). On the other hand, haplotype relationships among the individuals reveal that approximately 25% of the Korea salmons consist genetic lineages independent of Japan salmons and also that a genetic lineage exists in the Puk river and the Namdae river salmons independent of the Wangpi river salmons of Korea.