• Korean Journal of Remote Sensing
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• v.34 no.2_1
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• pp.237-248
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• 2018

The vertical distribution of hydrometeor before precipitation near the cloud base has been analyzed using a scanning lidar, rawinsonde data, and Cloud-Resolving Storm Simulator (CReSS). This study mostly focuses on 13 Desember 2016 only. The typical synoptic pattern of lake-effect snowstorm induced easterly in the Yeongdong region. Clouds generated due to high temperature difference between 850 hPa and sea surface (SST) penentrated in the Yeongdong region along with northerly and northeasterly, which eventually resulted precipitation. The cloud base height before the precipitation changed from 750 m to 1,280 m, which was in agreement with that from ceilometer at Sokcho. However, ceilometer tended to detect the cloud base 50 m ~ 100 m below strong signal of lidar backscattering coefficient. As a result, the depolarization ratio increased vertically while the backscattering coefficient decreased about 1,010 m~1,200 m above the ground. Lidar signal might be interpreted to be attenuated with the penetration depth of the cloud layer with of nonspherical hydrometeor (snow, ice cloud). An increase in backscattering signal and a decrease in depolarization ratio occured in the layer of 800 to 1,010 m, probably being associated with an increase in non-spherical particles. There seemed to be a shallow liquid layer with a low depolarization ratio (<0.1) in the layer of 850~900 m. As the altitude increases in the 680 m~850 m, the backscattering coefficient and depolarization ratio increase at the same time. In this range of height, the maximum value (0.6) is displayed. Such a result can be inferred that the nonspherical hydrometeor are distributed by a low density. At this time, the depolarization ratio and the backscattering coefficient did not increase under observed melting layer of 680 m. The lidar has a disadvantage that it is difficult for its beam to penetrate deep into clouds due to attenuation problem. However it is promising to distinguish hydrometeor morphology by utilizing the depolarization ratio and the backscattering coefficient, since its vertical high resolution (2.5 m) enable us to analyze detailed cloud microphysics. It would contribute to understanding cloud microphysics of cold clouds and snowfall when remote sensings including lidar, radar, and in-situ measurements could be timely utilized altogether.

• Asian Journal of Turfgrass Science
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• v.24 no.2
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• pp.106-116
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• 2010

This research was conducted to determine the effect of interruption layer for capillary rise on the sand based growing media when growing Kentucky bluegrass (Poa pratensis L.) on soil reclamation and saline water irrigation. Growing media profile consists of three layers as top soil of 30 cm, 20 cm of the interruption layer for capillary rise and 10 cm of reclaimed paddy soil. Growing media profile was packed in 30 cm diameter column pots. The top soil was a mixture of sand dredged up from Lake Bhunam Tae Ahn, Korea and peat at the ratio of 95:5 by volume. Bottom part of column was covered with plastic net and the pots were soaked into 5 cm depth saline water reservoir with salinity $3-5\;dS\;m^{-1}$. Kentucky bluegrass was established by sod and irrigated using $2\;dS\;m^{-1}$ saline water ($5.7\;mm\;day^{-1}$) in 3 days interval. The results showed that the largest accumulation of salt in the spring with electrical conductivity in saturated extract (ECe) of $5.4\;dS\;m^{-1}$ and sodium absorption ratio (SAR) 34.0 in growing media without the interruption layer for capillary rise and ECe of $4.6\;dS\;m^{-1}$ and SAR 8.24 at growing media using gravel as the interruption layer for capillary rise material. The interruption layer for capillary rise of gravel and coarse sand reduced the accumulation of Na by 16% and 25%, ECe by 7% and 13% in the growing media. Visual quality of Kentucky bluegrass was higher in growing media with the interruption layer for capillary rise of gravel than no interruption layer by 8.3 compared to 7.9 in rates. The interruption layer for capillary rise of gravel and coarse sand enhanced the visual quality by 4.1 and 4.0%, root length by 50 and 38%, and root dry weight by 35 and 17% of Kentucky bluegrass, and reduced the accumulation of Na by 16% and 25%, ECe by 7% and 13% in the growing media.

• Journal of Korean Society of Environmental Engineers
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• v.36 no.4
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• pp.286-294
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• 2014

The purpose of this study is to investigate the effects of applying density current generator (hereafter referred to as DCG to large lakes on the operating conditions of DCG, de-stratification, water quality improvement and inhibition of algae occurrence. As a result of a survey conducted to derive the optimum operating parameters of DCG in a condition to minimize eco-toxicity, the following conclusions were obtained. During the survey period, a marked stratification appeared in September to October 2011 and May 2012. At this time, the average depth of water to form thermocline was found to be $5{\pm}2$ m, so the location of discharge port for the operation of DCG was determined to be about 5 m below from the surface. To minimize the adverse effects of benthos and obtain the effect of water mixture at the time of water circulation, the mixing ratio of surface water and deep water was designed to be 3:1 by means of ecotoxicological assessment on the DCG operating characteristics. To select the appropriate operating hours for DCG, DCG was operated by 12 hr, 24 hr, 36 hr and 48 hr. As its result, the formation of thermocline did not occur during the operation of 36 hr. Also, It was effected that start reoperating from 3rd day after stop 2days under the condition of operated during 36 hr with calculated power consumption. Under the above conditions, the results of DO and water temperature analysis during the operation of DCG showed that the stratification, which was distinct previously, appeared to be weak, and relatively lower levels than those before operation were found as a result of water quality analysis on COD and chlorophyll-a, which leads to the conclusion that the water body is maintained at a stable condition due to the circulation of water by the occurrence of density current resulting from the operation of DCG.

• Journal of Wetlands Research
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• v.12 no.3
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• pp.1-13
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• 2010

Most of investigations about the effects of dam construction on the surrounding environments have focused mainly on the change of climate conditions and crop production. In order to research the effect of dam construction on the surrounding vegetation, we chose the Soyanggang dam whose storage capacity is the largest in Korea, and was built 33 years ago. We surveyed and analyzed the surrounding vegetation by using quadrat method and measured the soil moisture content among floodplain (FP), 5m above the flood plain (AFP) and control group (CG) which is 3km far from the lake through ridge. The largest value of mean importance percentage of the canopy~understory layer at FP was Salix koreensis (87.9%) and those of AFP and CG was Quercus mongolica (38.9% and 40.4% respectively) and the largest important percentage of the herb layer at FP was Artemisia capillaris (34.2%) and those of AFP and CG was Oplismenus undulatifolius var. undulatifolius (9.4% and 24.6% respectively). The Shannon-Wiener diversity index of shrub~canopy layer at FP (0.26) was lower than AFP (2.34) and CG (2.23) and there was not any significant difference in the herb layer among three groups. The S${\o}$rensen similarity index between FP and AFP, FP and CG was 0, and that of AFP and CG was relatively high. The highest density of tree and subtree with the DBH level of FP was S. koreensis of 5~10cm (240/ha), and that of AFP and CG was Quercus spp. of 15~20cm (400/ha and 466/ha respectively). And the highest density of seedlings of FP was Pinus densiflora (7,040/ha), and that of AFP and CG was Quercus spp. (720/ha and 400/ha respectively). The soil water content of FP (6.28%) was relatively lower than AFP and CG (11.13% and 10.14% respectively; p<.01). These results indicated that construction of Soyanggang dam changed the vegetation of the floodplain, without showing a change in its upland areas.

• Korean Journal of Ecology and Environment
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• v.41 no.spc
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• pp.50-60
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• 2008

We performed the experiment to evaluate the effect of different DO concentrations (0.5, 4.5 and 9.0 $mgO_2L^{-1}$) and water depths (20, 50 and 80 cm) on the filtering rate, mortality, and pseudifeces production of Unio douglasiae against the cyanobacterial bloom (mainly Microcystis aeruginosa). A solitary-living bivalve U. douglasiae was collected in the upstream region of the North Han River (Korea). The harvested mussels were carefully transferred to the laboratory artificial management system, which was controlled temperature $(18{\pm}2^{\circ}C)$, flow rate (10L $h^{-1}$), food $(Chlorella^{TM})$, sediment (pebble and clay), light intensity (ca. $20{\mu}mol$ photons), and photocycle (12 L : 12 D). In the field observation, the mussel mortality was significantly correlated with water temperature, pH and DO concentration (P<0.05). The mortality was decreased with water depth; 65, 90, 80% of mortality at 20, 50, 80 cm water-depth, respectively. Filtering rate (FR) showed the highest value at 50 cm water depth, and thereby the concentration of chlorophyll-${\alpha}$ decreased continuously by 94% of the control at the end of the experiment. In contrast, FR decreased by 34% of the initial concentration at 20 cm water depth. Over the given water-depth range, the mussel FR ranged from $0.15{\sim}0.20L\;gAFDW^{-1}hr^{-1}$ during the 18hrs of experiment, and thereafter, they appeared to be approximately 0.11, 0.26 and 0.30 L $gAFDW^{-1}hr^{-1}$ at 20, 50 and 80cm water depth, respectively. FR was highest with the value of 0.46L $gAFDW^{-1}hr^{-1}\;at\;0.5mgO_2 L^{-1}$ at the early stage of the experiment, while it increased with DO concentration. Maximum pseudofaeces production was 11.2 mg $gAFDW^{-1}hr^{-1}\;at\;9.0mgO_2L^{-1}$. Our results conclude that U. douglasiae has a potential to enhance water quality in eutrophic lake by removing dominant cyanobacteria, but their effects vary with environmental parameters and the water depth at which they are located.

• Proceedings of the Turfgrass Society of Korea Conference
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• 2011.02a
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• pp.5-8
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• 2011

This research was conducted to determine the effect of capillary rise interruption layer on the sand based growing media when growing Kentucky bluegrass under soil reclamation and saline water irrigation. Rootzone profile consists of three layers as top soil of 30 cm, 20 cm of capillary interruption layer and 10 cm of reclaimed paddy soil. Rootzone profile was packed in column pots. The top soil was a mixture of sand dredged up from Lake Bhunam Tae Ahn, Korea and peat at the ratio of 95:5 by volume. Bottom part of column was covered with plastic net and the pots were soaked into 5 cm depth saline water reservoir with salinity $3-5dsm^{-1}$. Kentucky bluegrass was installed by sod and irrigated using $2dSm^{-1}$ saline water(5.7mm $day^{-1}$)in 3days interval. The results showed that the largest accumulation of salt in the spring with ECe of $5.4dSm^{-1}$ and SAR34.0 in rootzone with out capillary rise interruption layer and ECe of $4.6dSm^{-1}$ and SAR8.24 at rootzone using gravel as capillary rise interruption layer material. Kentucky bluegrass grown in growing media with gravel as capillary rise interruption layer resulted in the average visual quality rate of 8.1and clipping dry weight of $24.8gm^{-2}$, while Kentucky bluegrass grown in the growing media with out capillary rise interruption layer showed the visual quality rate of 7.9 and clipping dry weight of $34g.m^{-2}$. Capillary rise interruption layer of gravel and coarses and enhanced the visual quality by 4.1and 4.0%, root length by 50 and 38%, and root dryweight by 35and 17% of Kentucky bluegrass, and reduced the accumulation of Na by 16% and 25%, ECe by 7% and 13% in the rootzone.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.33 no.4
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• pp.348-355
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• 2000

This paper described the relationship between the behavior of the Israeli carp, Cyprinus carpio and the environmental noise level due to the dynamite explosion work. The experiment was conducted in the cage ($L10{\times}W4{\times}D4 m$) of aquaculture located at Chungjoo Lake, Chechon, in 1997. The fish trajectory was obtained by the telemetry system in which a pulsed ultrasonic pinger ($50 kHz, {\phi}16{\times}L70 mm$) attached to the fish was tracked three dimensionally, and the underwater noise levels were measured. The results of the study were as follows: 1. The underwater noise levels in the normal blasting measured at a distance of 400 m from the source of noise increased by $40 dB (re 1 {\mu}Pa)$ compared to the levels before explosion. The dominant frequency and the increased power spectrum level of the underwater noise by the explosion work were $75 to 100 Hz and 22.9 to 35.3 dB$, respectively. 2. The underwater noise levels in the test blasting measured at a distance of 350 m from the source of noise increased by average $49.5 dB (re 1 {\mu}Pa)$compared to the levels before explosion. 3. The swimming area of the fish was reduced with the time after explosion, and after more than one hour the fish represented the similar swimming area and behavior to the status of right before explosion. 4, The swimming depth layer of the fish was most of the case at the sea surface less than 1,0 m except during explosion or right after of it. But the fish swam downward when an external stimulus like the explosion noise was given to the fish. 5. The average swimming speeds of the fish before, during and after the works were about 1.2 times, 1.9 times and 1.0 times of the body length, respectively, and the speed of the fish with explosion was faster 1.6 times than the speed without of that. Consequently, the explosion noise levels measured by this study were sufficiently high to affect the fish, and the heavy shock by the explosion works could produce a considerable unfavorable effects to the fish.

• Restorative Dentistry and Endodontics
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• v.26 no.4
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• pp.263-272
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• 2001

The aim of this study was to investigate the influence of four different light curing modes on the marginal leakage of Class V composite resin restoration. Eighty extracted human premolars were used. Wedge-shaped class Y cavities were prepared on the buccal surface of the tooth with high-speed diamond bur without bevel. The cavities were positioned half of the cavity above and half beyond the cemento-enamel junction. The depth, height, and width of the cavity were 2 mm, 3 mm and 2 mm respectively. The specimens were divided into 4 groups of 20 teeth each. All the specimen cavities were treated with Prime & Bond$^{R}$ NT dental adhesive system (Dentsply DeTrey GmbH, Germany) according to the manufacturer's instructions and cured for 10 seconds except group VI which were cured for 3 seconds. All the cavities were restored with resin composite Spectrum$^{TM}$ TPH A2 (Dentsply DeTrey GmbH, Germany) in a bulk. Resin composites were light-cured under 4 different modes. A regular intensity group (600 mW/${cm}^2$, group I) was irradiated for 30 s, a low intensity group (300 mW/${cm}^2$, group II) for 60 s and a ultra-high intensity group (1930 mW/${cm}^2$, group IV) for 3 s. A pulse-delay group (group III) was irradiated with 400 mW/${cm}^2$ for 2 s followed by 800 mW/${cm}^2$ for 10 s after 5 minutes delay. The Spectrum$^{TM}$ 800 (Dentsply DeTrey GmbH, Germany) light-curing units were used for groups I, II and III and Apollo 95E (DMD, U.S.A.) was used for group IV. The composite resin specimens were finished and polished immediately after light curing except group III which were finished and polished during delaying time. Specimens were stored in a physiologic saline solution at 37$^{\circ}C$ for 24 hours. After thermocycling (500$\times$, 5-55$^{\circ}C$), all teeth were covered with nail varnish up to 0.5 mm from the margins of the restorations, immersed in 37$^{\circ}C$, 2% methylene blue solution for 24 hours, and rinsed with tap water for 24 hours. After embedding in clear resin, the specimens were sectioned with a water-cooled diamond saw (Isomet$^{TM}$, Buehler Co., Lake Bluff, IL, U.S.A.) along the longitudinal axis of the tooth so as to pass the center of the restorations. The cut surfaces were examined under a stereomicroscope (SZ-PT Olympus, Japan) at ${\times}$25 magnification, and the images were captured with a CCD camera (GP-KR222, Panasonic, Japan) and stored in a computer with Studio Grabber program. Dye penetration depth at the restoration/dentin and the restoration/enamel interfaces was measured as a rate of the entire depth of the restoration using a software (Scion image, Scion Corp., U.S.A.) The data were analysed statistically using One-way ANOVA and Tukey's method. The results were as follows : 1. Pulse-Delay group did not show any significant difference in dye penetration rate from other groups at enamel and dentin margins (p>0.05) 2. At dentin margin, ultra-high intensity group showed significantly higher dye penetration rate than both regular intensity group and low intensity group (p<0.05). 3. At enamel margin, there were no statistically significant difference among four groups (p>0.05). 4. Dentin margin showed significantly higher dye penetration rate than enamel margin in all groups (p<0.05).

• Korean Journal of Ecology and Environment
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• v.37 no.3 s.108
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• pp.332-343
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• 2004

This study was conducted to test a possibility of water quality improvement using a filter-feeding bivalve (Corbicula leana). In mesocosm scale (width ${\times}$ length ${\times}$ depth: 3 m ${\times}$ 3 m ${\times}$ 0.5 m), we investigated the changes of dissolved nutrient and particulate matter including both abiotic and biotic seston. Short term (16 days) mesocosm experiment was conducted in two stages: the first stage for 8 days and consecutive 8 days of the second stage. Both treatment and control mesocosm were switched over by translocating mussels from the treatment mesocosm to the control, at 8th days since the start of the experiment. This design made it possible to compare mussel effect on the water quality change more clearly. The high mortality of mussel was observed in the treatment of the first stage, but it decreased rapidly and stabilized on the 8th day to less than< 4 ind $day^{-1}$. Chl. a concentration in the treatment mesocosm of the first and second stage decreased to 71 and 88% of initial concentration, respectively, and suspended solids decreased to 70 and 77%. At those times, average filtering rate were 0.46 and 0.61 mL AFDW $mg^{-1}$ $hr^{-1}$, respectively. Both $NH_3-N$ and dissolved total phosphorus (DTP) concentrations increased with the mussel mortality. $NH_3-N$ concentration was positively correlated with the mussel mortality, while DTP concentration showed negative correlation with it. After translocating mussel from the treatment to the control, $NH_3-N$ concentration significantly increased compared with that of initial control. Although DTP concentration also increased, there was no significant difference relative to that of initial control. These results suggest that application of this filter-feeding bivalve in a eutrophic reservoir could be a potential tool to improve water quality if mussels could acclimatize successfully in early stage of the introduction.

• Korean Journal of Ecology and Environment
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• v.48 no.2
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• pp.108-114
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• 2015

Single - and combined effects of a domestic freshwater bivalve Unio douglasiae (7.6~8.6 cm in shell length) and zooplankton Daphnia magna (1~2 mm in body size) were examined to understand whether they inhibit the growth of harmful cyanobacterial bloom (i.e. Microcystis aeruginosa) in a eutrophic lake. The experiments were triplicated with twelve glass aquaria (40 L in volume); three aquaria without mussel and zooplankton, served as a control, three zooplankton aquaria (Z, density=40 indiv. $L^{-1}$), three mussel aquaria (M, density=0.5 indiv. $L^{-1}$), and three mussel plus zooplankton aquarium (ZM, density=40 indiv.Z $L^{-1}$ plus 0.5 indiv.M/L), respectively. Algal growth inhibition (%) calculated as a difference in the concentration of chlorophyll-a (Chl-a) before and after treatment. Chl-a in all aquaria decreased with the time, while a greatest algal inhibition was seen in the ZM aquaria. After 24 hrs of incubation, Chl-a concentration at the mid-depth (ca. 15 cm) in ZM aquaria reduced by 90.8% of the control, while 63.2% and 79.8% in Z and M aquaria, respectively. Interestingly, during the same period, the surface Chl-a was diminished by 51.9% and 65.4% relative to the control in Z and ZM aquaria, while 27.4% of initial concentration decreased in M aquarium, respectively. These results suggest that 1) this domestic freshwater filter-feeding bivalve plays a significant role in the control of cyanobacterial bloom (M. aeruginosa), and 2) the combination with zooplankton and mussel has a synergistic effect to diminish them, compared to the single treatment of zooplankton and mussel.