• Journal of Korea Water Resources Association
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• v.54 no.2
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• pp.135-144
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• 2021

This paper attempted to find implications for water resource management and water quality improvement by analyzing the causal relationship among discharge, water temperature and pollution index, which were expected to have a great effect on water quality with the rise of water temperature and precipitation change as the warming effect in recent years. For this purpose, the unit root test, cointegration test, and Granger causal test were carried out for 10 multi-purpose dams in Korean major water systems using time series data on discharge, water temperature, BOD, COD and DO. It was analyzed that the fluctuation of water temperature affected the pollution index more than the fluctuation of discharge volume. Also, Hapcheon dam and Chungju dam were the best water quality management dams based on the high causal relationship between water quality and discharge. The second rank was Daecheong dam. The third-ranking group were Yongdam and Andong dam, whose causal relationships between water quality and discharge were low. The last group were the remaining five dams.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.22 no.5
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• pp.316-325
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• 2010

Harmonic analyses are carried out in order to obtain the major frequency components of the air temperature (AT) and surface water temperature (SWT) data monitored in the Middle Area of the Yellow Sea (Yellow Sea monitoring buoy). The analysis shows the annual and semi-annual components are predominant and the higher frequency components are relatively weak with contribution to the short fluctuations, i.e. below $0.2{\sim}0.5^{\circ}C$, in the AT and SWT. The standard deviation of the AT residual is 2.4 times larger than that of the SWT residual and the occurrence frequency distributions of the AT and SWT residual components are both closely fitted to a normal-distribution function. The variation pattern on the AT-SWT plane forms the clear continuous hysteresis loop in anti-clockwise direction which is composed of the AT-SWT rising period, AT-SWT falling period, and the constant SWT period in winter season.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.7 no.2
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• pp.43-50
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• 2002

This study focused on variability of the sea water temperatures observed off the Dangjin Power Plant in the central west coast of Korea for the period of 1998-1999. Spatial averaged temperature shows the annual range of $20.3^{\circ}C$, with minimum of $3.3^{\circ}C$ in February and maximum of $23.6^{\circ}C$ in August. Horizontal distribution patterns are seasonally reversing: The temperatures are increasing toward inshore of the period of April to October, while they are increasing toward of offshore for the rest of year. Spectral analyses of temperature records show significant peaks at M2 and S2 tidal periods, since the water movement in the study area is influenced by strong tide. The responses of temperature variations to tidal phase show different seasonal characteristics: The temperatures are increasing at flood phases in winter and ebb phases in summer. Amplitudes of the components at M2 and S2 periods are $0.8^{\circ}C\;and\;0.5^{\circ}C$, accounting for 70-80% of daily variation. Coherency analyses between non-tidal components of temperature and wind speed show that in summer, northerly wind components significantly coherent with temperature at 2.8 days period, while in winter, southerly wind component is coherent with 2.4 days period, with 0.6 and 0.7 day phase-lags, respectively.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.31 no.1B
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• pp.71-85
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• 2011

Saltwater intrusion effects of coastal aquifers in Korea peninsula were analyzed through trend analysis with groundwater level, seawater level, seawater temperature, and electrical resistivity(EC) data sets. Groundwater level and EC data sets from 27 coastal regions were collected and analyzed. Groundwater level was stable for all the regions however EC data showed stable or changing trends (9 increasing, 10 stable, and 8 decreasing regions). Seawater temperature was collected and analyzed for 14 regions and they are increasing for most regions (12 increasing and 2 stable regions). Seawater level was also collected and analyzed for 24 regions and is rising for most regions (18 rising, 3 stable, and 3 falling regions). Especially, west cost regions have stronger increasing tendencies of seawater level, seawater temperature, and EC than eastern and southern coastal regions. Therefore the saltwater intrusion problem can be serious for west cost regions in Korea peninsula and it is necessary to establish a plan to minimize the damages from saltwater intrusion.

• Korean Journal of Ichthyology
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• v.7 no.1
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• pp.43-55
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• 1995

Based on the reproductive cycle of Rhodeus uyekii, the reproductive control mechanism was examined under the several combinations of photoperiod and temperature regimes at different phases of their reproductive cycle. In early spring, the gonads developed rapidly under the warm temperature condition(above $8^{\circ}C$), regardless of the photoperiod. In late spring or early summer, gonads intensely regressed under the high temperature condition(above $24^{\circ}C$), regardless of the photoperiod. Thus, it is concluded that the spawning period of R. uyekii is initiated by the rising of water temperature in spring and is terminated by the high temperature in early summer. In autumn, the gonadal recrudescence occurs under the conditions of artificial long daylength with warm temperature(15L/9D, $12^{\circ}C{\sim}20^{\circ}C$), whereas the gonads remain in the existing condition under the short daylength. Therefore, in autumn the gonadal recrudescence is prevented by the short daylength although the temperature is still in favorable condition. In bitterling, the responsiveness of the gonads to photoperiod varies clearly with seasons, which was declined during the winter but increased during the autumn. The critical photoperiod for maturation ranges 12~13 hours of light per day. The results indicate that the proper ranges of temperature and photoperiod for gonadal maturation of this species are from $8^{\circ}C$ to $8^{\circ}C$ and from 13L to 15L, respectively.

• Journal of Aquaculture
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• v.3 no.1
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• pp.79-88
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• 1990

In order to obtain the basic data fir the effective seed production of sea squirt, Halocynthia roretzi(Drasche), the influence of water temperature and light intensity on spawning induction, egg development and seed settling were investigated during the Period from December 24, 1906 to February 24, 1987. The maximum number of eggs spawned was obtained at $14^{\circ}C$. The relationships between the water temperature (T, $^{\circ}C$) and the required time (h, hour) in each egg developmental stage were given as follows : Up to 8 cell 1/h =0.0147 T-0.0069(.=0.9816), Up to 32 cell 1/h =0.0100 T-0.0017(r=0.9672), Up to early tadpole 1/h =0.0043 T+0.0024(r=0.9913), Up to hatching larva 1/h =0.0021 T-0.0021 (r=0.9898). The highest rate of seed attachment was obtained at $14^{\circ}C$ of water temperature.

• Journal of fish pathology
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• v.23 no.1
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• pp.27-35
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• 2010

Pathogens on the cultured 579 rockfish, Sebastes schlegeli in the marine cage farms from Geoje and Tongyeong of the Southern sea were investigated from 2006 to 2008. The pathogens were detected throughout the year at 46.0~90.0% for 3 years and the detection rate was low with an average 58.1% in May and high with an average 81.5% in October. Bacteria only, bacteria-parasite mix and virus only were found in October and November as well as parasite only, whereas infection of parasite only was dominant in May when the temperature increased and in August when the temperature peaked. Of rockfish, Microcotyle sp. and Caligus sp. were dominant for parasitic disease, and Vibrio sp. and Streptococcus sp. were dominant bacteria. For virus, RSIV and VNNV were detected as dominant organisms. While no virus was detected in 2006, VNNV, VHSV and RSIV were detected in 2007 due to $1.5\sim2.0^{\circ}C$ higher temperature than 2006 in the summer season. For total prevalence by rockfish sizes, the highest was found at 50.0~87.1% in 11~15cm sizes and 50% was found in 30 cm size. Parasite showed a similar trend of 50.0~79.6% as the total prevalence. Prevalence for bacteria varied from 1.6% (for 10 cm group) to 23.8% (for 26 cm group) and higher virus prevalence of 21.5% was found from below 25 cm group.

• Journal of Korean Society of Environmental Engineers
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• v.31 no.11
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• pp.989-996
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• 2009

In this study, the effects of biofilter media type (three different activated carbons and anthracite), empty bed contact time (EBCT) and temperature on the removal of four aldehyde species (formaldehyde, acetaldehyde, glyoxal and methylglyoxal) in BAC filters were investigated. Experiments were conducted at three water temperature (5, 15 and $25^{\circ}C$) and four EBCTs (5, 10, 15, and 20 min). The experimental results indicated that the coal based BAC retained more bacterial biomass on the surface of the activated carbon than the other BACs, and increasing EBCT or increasing water temperature also increased the four aldehyde species removal in BAC filters. To achieve above 80% of removal efficiency for four aldehyde species in a BAC filter, above 15 min EBCT at $5^{\circ}C$ and 10 min EBCT at above $15^{\circ}C$ were required. The kinetic analysis indicated a first-order reaction rate for the biodegradation of four aldehyde species at various water temperatures. Data obtained from the BAC filters at various temperatures were also used to evaluate pseudo first-order rate constants for four aldehyde species. The half-lives evaluated for formaldehyde, acetaldehyde, glyoxal and methylglyoxal in the coal-based BAC ranging from 0.89 to 3.19 min, from 0.75 to 3.35 min, from 2.16 to 4.72 min and from 1.49 to 3.86 min, respectively, could be used to assist water utilities in designing and operating BAC filters.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.20 no.6
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• pp.489-500
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• 1987

Annual reproductive cycle of Bluegill, Lepomis macrochirus (RAFINESQUE) were studied in the natural population. Based on these informations, reproductive mechanism of the fish including activation, degeneration and remature were examined under the controlled conditions of temperature and photoperioe. In the natural populations, gonads began to grow with the temperature increase in March ana matured in June, and spawning occurred in July. With the onset of the shorter day-length and the maximum temperature condition in August, the gonads began to degenerate. Resting stage was continued during winter season. In the laboratory-reared population, activation of the gonads was initiated by the complex environmental factors including higher temperature$(>15^{\circ}C)$ and longer photoperiod $(>14L)$. For the maturation, photoperiod of more than 14 hours was critical. Under this condition higher temperature was the only compensative factor. Regeneration of the gonads was induced by higher temperature$(>25^{\circ}C)$ and the shorter photoperiod accelerated the regenerative processes. Even from the resting stage the gonads can be induced to matured stage by the longer photoperiod $(>15L)$. Based on these observations, the reproductive rhythm of this fish is supposed to be artificially controlled.

• Korean Journal of Remote Sensing
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• v.25 no.1
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• pp.1-10
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• 2009

We studied on the relationship between oceanic variation in the offshore and abnormal sea surface temperature rise in the coastal area of the Yellow Sea using a variety of satellite and in-situ data during winter 2004. In results of the satellite data, the average value of sea surface temperature in the Yellow Sea for 2003 was $10^{\circ}C$, and the average value of sea surface temperature for 2004 was $13^{\circ}C$. It was higher than those of the last year about $3^{\circ}C$. In results of the in-situ data, the average value of surface layer temperature in the Yellow Sea for 2003 was $9.85^{\circ}C$, and the average value of surface layer temperature for 2004 was $12.17^{\circ}C$. In the same satellite data, it was higher than those of the last year about $3^{\circ}C$. In results of the T-S diagram, we divided definitely into water mass of the Yellow Sea and the East China Sea in 2003. But we didn't divide definitely into water mass of the Yellow Sea and the East China Sea in 2004. The average values of air temperature and wind speed for 2003 were $5.23^{\circ}C$ and 4.81 m/s, respectively. And, the average values of air temperature and wind speed for 2004 were $5.61^{\circ}C$ and 4.52 m/s, respectively. So, These were similar. But the wind directions for 2003 were superior northwestern wind, and the wind directions for 2004 were various northern wind. The wind directions were different from each other. Therefore, the abnormal sea surface temperature rise in the coastal area of the Yellow Sea during winter 2004 were better related to oceanic variation in the offshore than influences of atmosphere. In the future, We will do in-depth study for these.