• Korean Journal of Fisheries and Aquatic Sciences
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• v.45 no.4
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• pp.343-350
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• 2012

Even though the microalgal species of Isochrysis and Pavlova are widely used as live food in bivalve hatcheries, they are difficult to culture in mass during the summer season. Therefore, the present study was conducted to determine the optimum species or strains of Isochrysis and Pavlova to produce good growth and high contents of fatty acids at temperatures over $30^{\circ}C$. Four species of Isochrysis (I. galbana KMMCC12, I. galbana KMMCC214, I. aff. galbana, and Isochrysis sp.) and four of Pavlova (P. lutheri, P. gyrans, P. viridis, and Pavlova sp.) were cultured at $25^{\circ}C$, $29^{\circ}C$, and $33^{\circ}C$, and then analyzed for specific growth rate and fatty acid composition. Microalgae were cultured in f/2 medium at 23 psu and continuous light of $80{\mu}mol$ photons $m^{-2}s^{-1}$. For the I. galbana, growth rates were highest at $29^{\circ}C$ and decreased at $33^{\circ}C$ to the level observed at $25^{\circ}C$. I. galbana (KMMCC12) and Isochrysis sp. cultured at $29^{\circ}C$ and $33^{\circ}C$, respectively, exhibited the highest growth rates of all Isochrysis species. In terms of fatty acids, I. galbana (KMMCC12) contained higher contents of PUFA and n-3 HUFA at $33^{\circ}C$ than did Isochrysis sp. For species of Pavlova, growth rates of P. gyrans and P. viridis at $29^{\circ}C$ and $33^{\circ}C$, respectively, were higher than those of the other Pavlova species. In particular, P. viridis grew as well at $33^{\circ}C$ as it did at $29^{\circ}C$. However, P. lutheri and Pavlova sp. did not grow at $33^{\circ}C$. In terms of fatty acids, P. viridis cultured at $33^{\circ}C$ also exhibited higher contents of PUFA and n-3 HUFA, as compared to P. gyrans. Based on these results, we suggest that I. galbana (KMMCC12) and P. viridis are suitable species for mass culture during the high temperature season.

• Journal of Embryo Transfer
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• v.32 no.3
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• pp.177-182
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• 2017

This study was conducted to investigate the ovarian cycle changes of the mare according to the season. Twenty four Jeju crossbred horses(Thoroughbred ${\times}$ Jeju horse) raised in Subtropical Livestock Research Institute, National Institute of Animal Science, RDA were used to identify follicles and corpus luteum with ultrasonography once a week(May 2016~June 2017). Blood samples of experimental horses were collected twice a week for analysis of P4 hormone levels. The mares were considered to have resumed ovarian cyclicity on the day of ovulation if they followed by regular ovarian cycles. Only 13 cases(61.9%) of the total 21cases showed normal ovarian cycle, and 8 cases (38.1%) showed delayed ovarian cycle. Three cases(16.7%) in October, 5 cases(27.8%) in November and 5 cases(27.8%) in December(27.8%) ceased the heat and the remaining 5 cases(27.8%) showed that the estrus was maintained in winter. Horses that stopped estrus ceased the heat until March of next year, and 27.8% were continued the heat during non-breeding season. Eleven cases(61.1%) of 18 cases in April and 2 cases(11.1%) of 18 cases in May returned the estrus.

• Korean Journal of Ecology and Environment
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• v.51 no.4
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• pp.354-364
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• 2018

In this study, we surveyed the fish community at the four sites(St. 1, 3, 5, 7) in Jungrang Stream from 2008 to 2016. We found 37 species grouped into nine families. There were three exotic species; Cyprinus carpio, Carassius cuvieri and Micropterus salmoides after rainfall. Dominant species was Zacco platypus (57.3%) and subdominant species was Carassius auratus(10.4%) in a community. The water quality, surveyed at the six sites(St. 1, 2, 3, 4, 5, 6), based on eight factors(Water temperature, pH, DO, BOD, SS, EC, TN and TP), largely varied depending on each site and period. Minimum values in four factors(BOD, EC, TN and TP) were observed in rainy season, indicating an ionic and nutrient dilution of stream water by precipitation. In contrast, a maximum value in SS was occurred in rainy season at St. 2 and St. 5. The precipitation, Maximum value observed in July ($497.5{\pm}297.2mm$), minimum value in January ($12.9{\pm}8.6mm$). In July and August, the precipitation was divided into before and after the rainfall season in Jungrang stream. Using cluster analysis three fish sites (St. 1, 3, 5) were identified as significantly influence 11 fish species; Hemiculter eigenmanni, Squalidus japonicus coreanus, Hemibarbus labeo, Gnathopogon strigatus, Pungtungia herzi, Rhynchocypris oxycephalus, Pseudogobio esocinus, Pseudorasbora parva, Cyprinus carpio, Carassius auratus and Zacco platypus by rainfall.

• Proceedings of the Korea Water Resources Association Conference
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• 2011.05a
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• pp.373-373
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• 2011

Korean Government has been promoting Four River Restoration Project (i.e., Han, Geum, Nakdong, and Yeongsan rivers) since the second half of 2008. This project is expected to protect against floods and droughts by water resources management. Many researchers have study water resources management, but most studies were focused on direct runoff. However, in order to efficiently protect against floods and droughts, baseflow should be studied as well as direct runoff. Because baseflow has a great effect on streamflow, it needs to be correctly analyzed. For more accurate analysis of baseflow, direct runoff and baseflow from streamflow should be separated first. In this study, 12 flow gauging stations of four major rivers were selected, and flow data from them were obtained (2004-2010) through WAMIS and Web-based SWAT Bflow system (http://www.envsys.co.kr/~swatbflow) which was used to separate direct runoff and baseflow. Baseflow values of Pass 2 in SWAT Bflow system were used. As a result of this study, baseflow contribution was ranged from 23.4% to 68.6% and accounted for about 50% of streamflow. Through this study, it shows that in the case of the flow fluctuation, baseflow is more affected than direct runoff by changes in streamflow in a flood or dry season. Thus, baseflow estimation should not be overlooked for efficient water resources management. However, it has a limitation in this study that because this study used to select randomly 12 flow gauging stations, it did not show a common tendency on each watershed. It is important that flow gauging stations reflected on topographic characteristics of each watershed should be selected in a rigorous manner for further reliable and accurate baseflow estimation on four major rivers.

• Asian Journal of Turfgrass Science
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• v.22 no.1
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• pp.25-34
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• 2008

This study was conducted to determine the optimum dose ranges for a mutation breeding based on the observations of a seed germination and an early growth in turfgrasses. Three warm season (Zoysiagrass, Bermudagrass, and Seashore paspalum) and four cool season turfgrasses (Kentucky bluegrass, Tall fescue, Perennial ryegrass, and Creeping bentgrass) were used in this study. We investigated the percentage of a seed germination and a seedling growth after irradiating the turfgrass seeds with various doses of gamma-ray (50, 100, 150, 200, 250, 300, 400, and 500 Gy). After 24 h with a gamma irradiation, the seeds were sown on the wet filter paper in a petri dish and maintained for 3 weeks at 30$^{\circ}C$ for the warm season turfgrasses and at 25$^{\circ}C$ for the cool season turfgrasses. Data on a seed germination and a seedling growth with three replications were collected. The percentage of seed germination was decreased with an increase of the gamma-ray dose. Shoot and root growth, and the fresh weight were decreased significantly as the radiation dose was increased. A radiation dose indicating a 50% growth inhibition ($LD_{50}$) with a gamma irradiation was varied among those turfgrass species used, with the highest at about 500 Gy for bermudagrass and the lowest at 100Gy for tall fescue. The optimum dose for a gamma irradiation for a selection of turfgrass mutants was considered to be about 300, 150, 500, 150, 200, 100 and 200 Gy for zoysiagrass, seashore paspalum, bermudagrass, Kentucky bluegrass, perennial ryegrass, tall fescue, and creeping bentgrass, respectively.

• Journal of Aquaculture
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• v.18 no.1
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• pp.31-36
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• 2005

A feeding trial of two feeding rate (satiation and $80\%$ satiation) $\times$ four feeding frequency (three meals a day, two meals a day, one meal a day and one meal every two days) factorial design with three replications was carried out to investigate the optimum feeding frequency and rate for growth of flounder during the winter season. Juvenile flounder averaging 45 g were fed a extruded pellet for 60 days. Weight gain was affected by both feeding frequency (P<0.001) and feeding rate (P<0.01). The best weight gain obtained from fish fed two meals a day with satiation was not different from that of fish fed three meals a day with satiation and $80\%$ satiation. Feed efficiency and protein efficiency ratio of fish fed the diet three times daily were the highest among groups, but not different to other groups of fish except for one meal every two days with satiation and $80\%$ satiation feeding. Daily feed intake was affected by both feeding frequency and feeding rate (P<0.001), these values of fish fed two and three meals a day with satiation were the highest among the groups. Moisture, crude protein, crude lipid and ash contents of fish were not affected by both feeding frequency and feeding rate (P>0.05). The results of this study indicate that the optimum feeding frequency for the growth of juvenile flounder grown from 45 g to 53 g is two meals a day with satiation feeding during the winter season.

• Journal of Korean Society of Environmental Engineers
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• v.39 no.2
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• pp.89-96
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• 2017

This study analyzed the characteristics of water quality and the correlation between Chl-a and water quality factors among four weirs located in the middle and downstream of Nakdong River for five years. The concentration of nutrients and Chl-a from DS to CH was higher than that of GG, which is considered to be due to the influx of Kumho River located at upstream of DS. There was a significant correlationship between Chl-a and most of the water quality factors for all season data. Based on the comparison results between all season data and summer season data, a negative correlation between Chl-a and nutrients ($PO_4-P$, $NH_3-N$) was increased. Based on analysis on summer in 2015 with relatively low precipitation and high algal blooms, the correlation between Chl-a and $PO_4-P$ at all sites were increased. Therefore phosphorus is an important factor in the river on summer season. And PCA results showed the first factor was classified as T-N, $NO_3-N$ for all seasons, and the first factor was classified as T-P, $PO_4-P$ for summer seasons. Consequently, the middle and downstream of Nakdong River were most affected by nutrients, especially it was affected by phosphorous pollutants rather than nitrogen pollutants during summer seasons.

• Journal of Korea Water Resources Association
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• v.53 no.12
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• pp.1049-1057
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• 2020

This study aimed to develop a flow measurement method using drone in flood season. Measuring flow in all branches is difficult to conduct annually due to budget and labor limitation, safety and river works. Especially when heavy rain like storm comes, changes in stage-discharge relationship should be reviewed; however, it is usually impeded by the aforementioned issues. To solve the problem, it developed a simple measuring method with a minimum of labor and time. A numeric map and numeric orthophoto coordinate of South Korea are mostly based on Transverse Mercator Projection (TM) in accordance with rectangular coordinate system and use World Geodetic Reference System 1980 (GRS80) oval figure for conversion. Applying a concept of aerial photogrammetry, it located four visible Ground Control Points (GCP) near the river at Uijeongbu-si (Singok Bridge) and Yeongdong-gun (Youngdong 2nd Bridge) station and measured the coordinates using VRS DGPS. Hovering at a same level, drones took orthophoto of water surface at an interval of 3 seconds. It defined the pictures with GRS80 TM coordinate system, a rectangular coordinate system and then conducted an orthometric correction using GCP coordinates. According to X and Y coordinate analysis, it estimated the distance between the floating positions at 3 seconds-intervals and calculated the flow through the flow area according to the flow path. This study attested applicability of the flow measurement method using drone in flood season by applying the rectangular coordinate system based on the concept of aerial photogrammetry.

• Magazine of the Korean Society of Agricultural Engineers
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• v.30 no.4
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• pp.23-44
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• 1988

The evaportranspiration of upland crops was measured by four types of lysimeter and water consumption characteristics together with the optimum irrigation point by the crops was defind. Among the evapotranspiration estimation formulas, the constant of wind function in the modified Penman equation was corrected to agree with the meteorological conditions of Korea. The evapotranspiration of the crops in the project standard year was estimated according to the cropping system of the project area in Chungju, and from the estimated evapotras - spiration, net duty of water per one time and irrigation in tervals were investigated. The results obtained are summarized as follows: 1. The evapotranspiration of the same crop measured at the same plot was slightly different by the lysimetric methods, and among the four types of lysimeter, the accuracy of the floating lysimeter was the highest. 2. The yields among the watering treatments showed the significance of 5% in the expe- riment with red cabbage and Chinese cabbage, and significance of 1% in the crisphead lettuce, and the optimum irrigation point for the tested crops was defined ad pF 2.0 by the least squre difference test. 3. The evapotranspiration of the crops in the mid-season stage showed maximum among the growing stages, and the average daily evapotranspiration by the crops over the growing seasons of cabbage, crisphead lettuce, Chinese cabbage, summer cucumber, tornato, salary and autumn cucumber was 4.18mm, 4.77mm, 3.9qrnm, 5.68mnn, joonim, 4.26mm and 3.3qrnn, respectively. 4. From the investigated soil moisture extration pattern(SMEP) of the crisphead lettuce, cucumber and tomato, the proportion of the first layer in the initial stage showed over so%, and the SMEP of the lowest fourth layer during the late-season stage in the experiment cabbage and Chinese cabbage was 15.8% and 16.9, respectively, with showed that the root elongated th the lowest soil layer. 5. The total available moisture(TAM) of clay loam was 21.2-23.3mm and that of sandy loam was 16.1 - 19.0mm under the optimum irrigation point of pF. 2.0, and the total readily available moisture( TRAM) of the crops cultivated in the clay loam soil was larger than that cultivated in the sandy loam soil, and the TRAM during the mid-and late-season were larger than that of the inital and crop development stage. 6. The estimated evapotranspration by the corrected Pennam equation, whkh corrected the constant of the wind function in the modified Penman equation, was nearly agreed with the actually measured evaporanspiration of grass. 7. Among the several evaportranspiration estimation methods, the evapotranspiration es- timated by the corrected Pennam equation was closed to the actual evapotranspiration of reference crop (grass) evapotranspiration, therefore it is suggested to use the corrected Penman equation to determine the duty of water of corps. 8. The average crop coefficient (Kc) of cabbage by the corrected Penman equation was 0.94 and that of crisphead lettuce, summer cucumber, tomato, salary, Chinese cabbage and autumn cucumber was 1.07, 1.22, 1.02, 1.01, 1.35, 1.09, respectively 9. The estimated total evapotranspiration of cabbage in the project area( Chungju) by the corrected Penman equation was 223.9mm and that of crisphead lettuce, Chinese cabbage, summer cucumber, tomato, salary and auturun cucumber was 215.7mm, 205.9mm, 359.Omrn, 300.9mm, 332.lmm and 202.7mm, respectively. 10. The net duty of water per one time of the crops cultivated in the sandy loam soil, and the net duty of water per one time in the mid-season & late-season showed larger than that of the initial stage. 11. The shortest irrigation interval of cabbage in the project area was 4.2 days, and that of crisphead lettuce, Chinese cabbage, cucumber, tomato and salary was 1.2days, 2.3days, 1.8days, 2.2days and 2.7days, respectively.

• Korean journal of applied entomology
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• v.58 no.4
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• pp.313-317
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• 2019

Stink bugs (Hemiptera: Pentatomidae) are economically important pests of fruit trees in Korea. The aim of the present study was to survey the relative abundance of stink bugs on four stone fruits, maesil (Prunus mume Sieb. et Zucc), cherry (Prunus avium L.), plum (Prunus salicina Lindl), and peach (Prunus persica (L.) Batsch), from 2017 to 2019 in the field. Four stink bug species were observed, including Carbula putoni (Jakovlev), Dolycoris baccarum (L.), Halyomorpha halys (Stål), Plautia stali Scott. H. halys was the most abundant (65%), followed by P. stali (26%), C. putoni (7%), and D. baccarum (2%). H. halys was the dominant species in maesil, cherry, and peach fruits, whereas P. stali was the dominant species in plum fruits. Most (81%) of the stink bugs observed were adults, with nymphs accounting for only 19% of the observed specimens. More stink bugs were observed during the late season than during the early season. These finding suggest that control strategies should be developed for the management of H. halys and P. stali at harvest in stone fruit tree orchards in Korea.