• The Journal of Engineering Geology
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• v.18 no.2
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• pp.167-176
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• 2008

The variation characteristics of groundwater level with distance from shoreline at Jeju Island was investigated using groundwater level data monitored from 257 wells for dry season (December 1998) and wet season (July 1997), respectively. Groundwater levels of the dry season were $7.46{\sim}203.8\;m$ with an average of 60.49 m, while those of the wet season were $4.01{\sim}204.10\;m$ with an average of 57.66 m. Groundwater level of the dry season was higher than that of the wet season, which was caused by heavy rains between June and October, 1998 at the Jeju Island. Correlation coefficients between altitude and groundwater level for dry and wet seasons were above 0.86, and those between dry season and wet season groundwater levels were very high above 0.95. 257 groundwater level data were classified at an interval of 500 m. Average values for altitude, groundwater levels and distance from shoreline were calculated for 17 intervals. Altitude and groundwater level fur dry and wet seasons at $0{\sim}4\;km$ intervals were increased with distance from shoreline, but those at $4{\sim}9\;km$ intervals were irregularity. Linear functions of the groundwater level for dry and wet seasons as distance from shoreline were estimated, and the coefficient of determinant at $0{\sim}4\;km$ interval data was higher than it at $0{\sim}9\;km$ interval data. Increasing rate of groundwater level at $0{\sim}4\;km$ intervals was more 2 times than it at $0{\sim}9\;km$ intervals. This results are caused by linear increase of groundwater level to 4 km from shoreline and by irregularity of groundwater level at the $4{\sim}9\;km$ intervals.

• Journal of Educational Research in Mathematics
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• v.24 no.3
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• pp.333-357
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• 2014

This study resulted from a study regarding creative STEAM System based upon an experiment with the center of gravity. The results of the study are constructed by a fusion of mathematics and physics, showing that they are the same as mathematical calculations. Also, students can find that center of gravity of an object is in equilibrium on a metal rod when the center of gravity exactly is placed on the rod. The fact that an experimental results are correspond to calculations can maximize the effectiveness of teaching. And also this study has the following effectiveness. First, the exact construction and calculations arouses good competition among students. Second, this experiment can give students a motivation for study and increase their thinking in classes because the theoretical background of center of gravity experiment is basically attributed to math and science classes in school. This study includes three different types of center-of-gravity experiments. One is a simple type of experiment in which center of gravity exists inside of an object. Another is a complicated one in which the center of gravity is also inside of an object. However, the third type is an experiment in where the center of gravity is outside of an object. Therefore, it gives students an opportunity to discuss how to confirm equilibrium on a metal rod when the object has its center of gravity outside. Having discussions in class will allow students to have a critical way of thinking. In addition, searching for a way to solve a problem will increase creativity of students as well. And the last type is finding the center of gravity of a big acrylic panel where multiple objects are on the panel. According to the survey and interview conducted by students who participated in this program, teaching based on creative STEAM system helps students to get a better understanding and more fast acquisition of knowledge. We can expect that a well-planned creative STEAM system through a continuous study will be both effective and efficient in educating critical and creative students.

• Journal of Embryo Transfer
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• v.30 no.1
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• pp.45-50
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• 2015

The purpose of this study is to produce wanted sex progeny of genetically confined White Hanwoo (albinism) with preselected sex sperm. One bull of White Hanwoo was chosen for semen donor and X sperm was sorted by MoFlo XDP cell sorter. To compare the pregnancy and birth rates, KPN straw was used as control, total number of unsorted sperm was $20{\times}10^6/straw$. Sexed X frozen semen with $20{\times}10^6$ cells or $4{\times}10^6$ cells per straw were in seminated twice on Hanwoo heifers. The abnormality of the sexed X semen was $24.9{\pm}7.31%$ and distal reflex abnormality of mid piece was significantly (p<0.05) higher (11.7%) compared with that of KPN 768 (5.6%). There were no differences on the pregnancy and birth rates between $2{\times}10^6$ cells or $4{\times}10^6$ cells of X-sperm but KPN semen showed significant differences (p<0.05). The pregnancy rates of KPN 768, $2{\times}10^6$ cells and $4{\times}10^6$ cells X-sperm of White Hanwoo cattle were 85.0%, 26.3% and 50%. The birth rates were 80.0%, 15.8% and 21.4%, respectively. The female offspring rates of KPN 768, $2{\times}10^6$ cells and $4{\times}10^6$ cells X-sperm of White Hanwoo cattle were 43.8%, 100% and 100% (p<0.05). These results indicated that sex sorted White Hanwoo could be used for the production of wanted progeny with $2{\times}10^6$ cells/straw for AI. To increase the efficiency of calf production, the sperm number of sex sorted semen will be optimized for sex selection of White Hanwoo progeny.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.27 no.3
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• pp.183-192
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• 1982

The variability of rice productivity during last 2 decades (1961-1980) of ten years before and after the introduction of"Tongil" was reviewed from the epochal, regional and varietal points of view. During that period the cultivated area of paddy rice have remained almost unchanged, while the total rice production have got elevated from 3, 463 million metric tons in 1961 to 6.006 million metric tons in 1977, recording 73.4% increase. This remarkable increase in rice production is considered to be attributable much to the development and release of new high yielding variety, "Tongil", coupled with the amelioration of cultural techniques. However, in 1978 Tongil type varieties experienced the epidemic outbreak of blast disease due to the shifted race population of blast fungus and in 1980 recorded poor rice production as low as in 1960's due to the unfavorable weather stress throughout the rice growing season, giving rise to many problems awaiting solutions for securing the stabilized high production of rice. The rice yield has continued the gradual increase during last two decades but its difference between farmer and research organization have got wider from 79kg/10a during 1960 to 1971 to 101kg/l0a during 1972 to 1980, and also the inter-regional differences have been increased from 50-60kg/10a to 80kg/10a during those periods. Therefore, this proves that we have raised the upper boundary of rice yield by increasing the yield potential of rice variety but have not changed those absolute deviations. Estimates indicate that the increased rice production during that period was indebted 40 percent to the varietal improvement and 13 percent to the ameliorated agro-technologies, and the rest, 47 percent, could be ascribed to the other factors besides varieties and cultural technologies such as the improved agricultural environments, etc. Of course, even though it cannot be expected to unify the cultural environments and the cultural technologies, provided that much efforts are to be endeavored to minimize the yield difference of 20 percent between farmer and research organizations and the inter-regional yield difference of 20 percent, much increased rice production can be expected to be achieved with the current level of cultural technology and the yielding potential of the present rice varieties. In order to expedite the above effects on rice production the followings are to be put into practices consitently and steadfastly. 1. Reinforcement of breeding for varieties with high yielding potential and less susceptible to climatic-stress and pests, and of basic physicoecological studies of rice plant for improving the cultural technologies. 2. Continuous endeavor to secure the stabilized cultural environments by improving the soil fertility and increasing the drainage and irrigation facilities. 3. Political back-up to encourage the farmers' incentives for production 4. Precise surveys for agricultural statistics to facilitate the long-term planninge long-term planning.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.42 no.6
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• pp.666-672
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• 1997

Twenty years' daily mean air temperature data was used to calculate the critical early seeding date(CESD), the optimum heading date(OHD), the critical late heading date for stable ripening(CHDR) and the critical late ripening date(CLRD) for rice seeded on dry paddy in different agroclimatic zones in Korea. The CESD was defined as the first day with mean air temperature of 13$^{\circ}C$, and the OHD as the first day of the 40 consecutive days with mean air temperature of 22$^{\circ}C$ or above after heading. The CHDR was defined as the date after which the cumulative daily mean air temperature would be at least 76$0^{\circ}C$. Lastly, the CLRD was defined as the last day when daily mean air temperature remains above 15$^{\circ}C$. This information was used for the estimation of periods from the earliest date of seeding to optimum heading date, the latest possible date of heading and the latest possible date of ripening in respective regions. For instance, in Suwon, those respective periods mentioned were found to be 104days, 124days, and 165days.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.61 no.2
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• pp.124-130
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• 2016

In this study, agronomic characteristics and fatty acid composition of 121 flax (Linum usitatissimum L.) germplasms were analyzed. The flax germplasms had a fairly short growth period of 75-95 days. The plant height at maturity varied from 52 to 124 cm. The flower color varied from white to lilac and even purple. Early flowering flax germplasms had white flowers and were resistant to lodging. In early flowering flax germplasms, all agronomic characteristics, including growth period, plant height, branch number per plant, stem diameter, number of capsules per raceme, seed number per capsule, 1000-seed weight, and seed yield, were decreased. The average fatty acid composition of 121 flax germplasms comprised palmitic acid (5.3%), stearic acid (4.3%), oleic acid (29.7%), linoleic acid (13.1%) and linolenic acid (46.4%). The total content of unsaturated fatty acids ranged from 84~94% with an average of 88%. Among the fatty acids, linolenic acid (omega-3) content was the highest with a range of 36~54%. In five selected flax germplasms (Hollandia 1803, Red son, C & F Res Br 1767, Wiera, and Ireland 1657) with high linolenic acid (${\geq}51%$), total lipid and protein contents were 30~36% and 5.4~6.9%, respectively. Overall, flax can practically be adoptable into cropping systems in South Korea and utilized as a scenery crop, since flax has a short cultivation period with diverse flower colors.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.57 no.1
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• pp.51-59
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• 2012

Contents of phenolics and flavonoids, antioxidant activity and cytotoxicity were investigated in the methanol extracts of three different $Taraxacum$ species, $Taraxacum$ $coreanum$, $Taraxacum$ $mongolicum$, and $Taraxacum$ $officinale$. Total phenolics content at $1000mg\;kg^{-1}$ was more present in shoot parts than in roots, and was highest in $T.$ $mongolicum$ shoot and root extracts (76.8 and $40.0mg\;kg^{-1}$, respectively), followed by $T.$ $coreanum$ and $T.$ $officinale$ ($p$ < 0.05). Total flavonoid level had same tendency to total phenolics among $Taraxacum$ species, showing lower amounts ($6.5{\sim}36.4mg\;kg^{-1}$) than total phenolics. The antioxidant activity of the methanol extracts from all the species dose-dependently increased. DPPH free radical scavenging activity at $1,000mg\;kg^{-1}$ was highest in shoot and root extracts from $T.$ $mongolicum$ by 89.6 and 83.4%, respectively. According to MTT assay, cell viability of Calu-6 (human pulmonary carcinoma) was lowest in the $T.$ $mongolicum$ shoot and root extracts ($IC_{50}$ values=83.4 and $66.4mg\;kg^{-1}$, respectively), and followed by $T.$ $coreanum$ and $T.$ $officinale$ (lowest). Calu-6 was more sensitive to the extracts than SNU-601 (human gastric carcinoma). Antioxidative and anticancer activities in three different $Taraxacum$ species was more correlated with total phenolics content ($r^2$=0.0097 to 0.6213) than with total flavonoids level ($r^2$=0.0027 to 0.4627). The results showed total phenolics content and total flavonoids level were highly correlated with anticancer activity and antioxidant activity, and their content and activities were different depending on species.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.55 no.2
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• pp.119-125
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• 2010

This study was carried out to compare the physicochemical characteristics of Korean traditional wine fermented from proso millet and nuruk at different mixing rate. The alcohol contents of the fermented wine ranged from 12.36 to 13.21%. Two kinds of nuruk, SH and BS nuruks were used. The brix degrees of proso millet wine fermented by SH and BS nuruks were 21.6 and 22.4 $^{\circ}Bx$, respectively. The pH, total acidity, and turbidity the wines fermented by SH and BS nuruks were 3.74 and 3.40, 1.40 and 1.51%, and 0.441 and 0.149, respectively. With increasing the addition amount of proso millet, brix degree, pH, turbidity L-value decreased, and total acidity and avalue increased. Total color difference (${\Delta}Eab$) parameter of the wine fermented by SH nuruk were 4.33, 6.63 and 26.13, and by BS nuruk were 4.08, 5.29 and 10.59 in 30, 70 and 100% addition rates of proso millet. With increasing the addition amount of proso millet, glucose content decreased. The organic acids such as lactic acid and acetic acid were predominantly detected in the fermented wine. Finally, based on sensory evaluations, the wine fermented by SH nuruk showed the best overall quality at 30% addition rate of proso millet.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.53 no.4
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• pp.394-400
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• 2008

Crop characteristics of 137 common millet (Panicum miliaceum L.) resources collected in Korea were investigated in order to establish basic data for the improvement of crop breeding. Spike types of 137 plant resources were classified as 4 types of oblate, spreading, oblate-compact (intermediary type between oblate and compact) and oblate-spreading (intermediary type between oblate and compact) type, of which oblate spike type was the highest percentage of 66.4% (91 plant resources) of 137 germplasm. Seed color was classified as 5 colors of dark brown, yellow, brown, yellowish brown, and yellowish white, of which yellowish white was the highest percentage of 66.4% (54 plant resources) among them. Seed type was classified as 2 types of pyramid shape and short pyramid shape, which showed 62.8% and 37.2% respectively. Days from seeding to heading date showed the range from 68 to 85 days with 73.7 days in the average and the highest frequency proportion of it was the group from 70 to 75 days, which occupied 46.7% (64 plant resources) of 137 germplasm. Days from seeding to physiological maturity showed the range from 109 to 124 days with 112.0 days in the average and the highest frequency proportion (60.6%) of it was the group from 111 to 115 days, while there were also occupied with 6.6% below 110 days and 5.1% over 120 days among 137 germplasm. Group from 181 cm to 190 cm of culm length showed the highest frequency proportion of 47.4%, whereas below 160 cm was the lowest occupancy of 2.9%. Spike length showed the range from 181 to 190 cm with 181.4 cm in the average and the highest frequency distribution of it was the group from 31 to 35 cm with the proportion of 54.0%. Number of grains per spike showed the range from 432 to 2,665 grains with 1,429.5 grains in the average and group from 1,200 to 1,400 grains per spike was the highest frequency distribution with the proportion of 20.4%. There were also occupied with 13.1% below 1,000 grains and 8.6% over 2,000 grains per spike among 137 germplasm.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.58 no.1
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• pp.1-7
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• 2013

The purpose of this study was to provide basic information for breeding cowpeas (Vigna unguiculata L.) by investigating the crop characteristics of 245 accessions of cowpea collected in Korea and abroad. All specimens flowered within 41 to 50 days (51.5%) or 51 to 60 days (43.7%) of sowing and matured 21 to 30 days (53.9%) or 31 to 40 days (23.7%) from flowering. Thus, the total time from sowing to maturity was either 71 to 80 days (26.9%) or 81 to 90 days (23.4%) for all specimens. The accessions were classified into indeterminate type (72.7%), intermediate type (25.7%) and determinate type (1.6%) based on growth; prostrate type (78.8%) and erect type (21.2%) based on plant type; heart shape (98.4%) and lanceolate (1.6%) based on leaflet shape; and purple (85.2%), white (13.6%) and light green (1.2%) based on corolla color. The accessions were classified into brown (54.7%) and yellowish brown (37.6%) based on color at pod maturity; and downward (90.6%), middle (5.7%) and standing upright (3.7%) based on pod setting position. Seed coat color varied as 25.3% were brown, 23.3% were black, and 20.8% were white. Seed shape also varied as 66.9% were egg-shaped, 24.9% were rectangular and 8.2% were kidney-shaped. Pod lengths ranged from 10.1-20.0 cm and from 20.1-30.0 cm in 89.0% and 8.6% of specimens, respectively. There were 12.1-15.0, 9.1-12.0, and 15.1-18.0 seeds per pod in 62.0%, 25.7% and 9.1% of specimens, respectively. The weight of one hundred seeds ranged from 15.1-20.0 g (37.6%) and 10.1-15.0 g (28.6%). Seed yields per plant were 100.1-200.0 g (52.7%), less than 100 g (22.9%), and 200.1-300.0 g (15.9%). The starch content in the seeds of the seven selected resources ranged from 44.1 to 57.0% while the protein content ranged from 23.3 to 27.5% with significant differences. The sucrose content ranged from 1.46 to 2.03%, also with significant differences.