• Proceedings of the Korea Water Resources Association Conference
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• 2006.05a
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• pp.864-868
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• 2006

댐과 양쪽의 산 능선에 감싸이어 있는 저수지의 모습은 이렇다할만한 특징을 찾아보기가 쉽지 않다. 우리나라의 각지에 건설되어진 다목적댐으로 인해 형성되어진 저수지들을 둘러보아도, 역시 주변의 지형을 자세히 비교해 보기 전에는 구별하기 힘들만큼, 그만큼 외관상으로는 닮아있다. 하지만, 이러한 저수지들이 보여주는 자연현상은 실제로는 너무나도 다양하다. 잔잔한 물 표면의 안쪽에 저마다 눈에 보이지 않는 특성들을 감추고 있으리라 추측해 본다. 하지만, 그 특성을 정량적으로 파악 하기란 좀처럼 쉽지가 않다. 영양염분의 과다 유입으로 부영양화가 초래되면 여기저기서 녹조를 발생 시키고, 또한 홍수나 상류 유역의 토사 붕괴로 인하여 좀처럼 침강되지 않는 미세 입자가 과다 유입되면, 1년 내내 누런 탁수로 몸살을 앓는다. 이처럼, 인간의 눈에 보여 지는 저수지는 '매우 닮은 모습에서 너무나 다른 모습'으로 '계단의 층계변화'와 같은 극단적인 상태 변화만이 파악되어진다. 최근에 들어서, 장비의 발달과 환경에 대한 관심의 고조로 한 달에 한번 많으면 일주일에 한 번씩 현장 조사를 수행하고는 있지만, 지속적으로 저수지를 파악하기 위한 '선형적인 현상'을 보여주기에는 충분하지가 않다. 본 연구에서는, 저수지 수온을 모니터링 함으로서, 홍수와 가뭄과 같은 이벤트 및 계절 변화로 인한 수체의 온도분포를 조사 하였다. 그 방법으로, 자체 개발한 써미스터체인을 용담호의 댐축 지점과 댐축으로부터 상류방향으로 6.6km 떨어진 유입지점의 두 곳에 설치하였으며, 연 중 10분 간격으로 수온데이터를 로거에 저장한 후, 두 달에 한번 정도로 센서 정비 및 데이터 수거를 실시하였다. 그 결과, 우리가 눈으로나 현지관측만으로는 파악할 수 없었던 수체내의 많은 특징을 파악 할 수 있었다.. 중랑천 유역의 소배수구역을 대상으로 연중 발생하는 큰 호우사상에 대해 임의의 강우관측소를 결측지점으로 가정하고 주변의 강우관측소로부터 각각의 방법을 이용해 가중치들을 산정하여 결측지점의 강우량 값을 보정하고자 하였다. 또한 각각의 방법을 이용하여 얻어진 결과에 대해 실측값과 보정값의 오차정도를 평균절대오차법(Mean Absolute Error)과 제곱평균제곱근오차법(Root Mean Squared Error)에 의해 산정하여 보정 방법간의 효율성을 검토하고자 하였다.9년, 그리고 2010년${\sim}$2019년까지 총 4구간으로 나누어 결과를 도출하였으며 예상한 바와 같이 후반기 20년 동안에 세 가지 지표가 취약해 지는 것을 확인할 수 있었고, 특히 2000년부터 2009년까지 10년 동안에는 더욱 취약해짐을 확인할 수 있었다.를 보임에 따라 그 정책적 효과는 때로 역기능적인 결과로 초래하였다. 그럼에도 불구하고 이 연구결과를 통하여 최소한 주식시장(株式市場)에서 위탁증거금제도는 그 제도적 의의가 여전히 있다는 사실이 확인되었다. 또한 우리나라 주식시장에서 통상 과열투기 행위가 빈번히 일어나 주식시장을 교란시킴으로써 건전한 투자풍토조성에 저해된다는 저간의 우려가 매우 커왔으나 표본 기간동안에 대하여 실증분석을 한 결과 주식시장 전체적으로 볼 때 주가변동율(株價變動率), 특히 초과주가변동율(超過株價變動率)에 미치는 영향이 그다지 심각한 정도는 아니었으며 오히려 우리나라의 주식시장은 미국시장에 비해 주가가 비교적 안정적인 수준을 유지해 왔다고 볼 수 있다.36.4%)와 외식을 선호(29.1%)${\lrcorner}$ 하기 때문에 패스트푸드를 이용하게 된 것으로 응답 하였으며, 남 여 대학생간에는 유의한 차이(p<0

• Journal of Wetlands Research
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• v.15 no.4
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• pp.535-541
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• 2013

The urbanization affects significantly on a natural water circulation system by increasing the imperviousness rate. It is also negatively affecting on urban temperature, environmental pollution, water quality, and aqua-ecosystems. The Korea MOE (Ministry of Environment) adapted a new environmental policy in order to reduce the impact of urbanization, which is the Green Stormwater Infrastructure (GSI) program. The GSI can be achieved by protecting conservable green spaces, enlarging more green spaces, and constructing more permeable pavements. The GSI is including many different techniques such as bioretention, rain garden, infiltration trench and so on. Also It is the infrastructures using natural mechanisms of soils, microorganisms, plants and animals on a water circulation system and pollutant reduction. In this research, a multi functional GSI technology with infiltration-filtration mechanisms has been developed and performed lab-scale tests to evaluate the performances about infiltration rate restoration and pollutant reduction. The most of pollutants including metals, organics and particulates were reduced about 50~90% due to water infiltration and storage functions. The clogging was found when the TSS loading rate was reached on $8.3{\sim}9.0kg/m^2$, which value is higher than the values in literatures. It means the new technology can show high performances with low maintenances.

• Journal of Sericultural and Entomological Science
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• v.34 no.2
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• pp.26-31
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• 1992

Flacherie virus (FV) and Densonucleosis virus (DNV) of the silkworm, Bombyx mori, which give the most severest damage to the silk production in korea, were fed on the mulberry wild silkworm, Bombyx mori mandarina, the mulberry pyralid, Gryphodes phyloalis, and the American fall webworm, Hypantria cunea, to investigate cross infectivity by serological and histopathological at observation. By the Ouchterlony's double difusion test the mulberry wild silkworm was infected with both FV and DNV type 1 (DNV-1) and the mulberry pyralid with DNV-1, so those were confirmed the cross infection. But the American fall webworm was not recognized the cross infection by the same method. The infection and multiplication of the FV in the mulberry wild silkworm was observed in the cytoplasm of the goblet cell with the appearance of the virus-specific vesicle. In DNV-1 infection to the mulberry wild silkworm and the mulberry pyralid, the nuclei of columnar cell in the midgut of both insects was hypertrophied and the nuclei of midgut cell of the mulberry pyralid positively stained with the feulgen stain. Multiplication of DNV-1 in the midgut cell of the mulberry wild silkworm was replicated in two different patterens as linear arrays and large masses, while that of DNV-1 in the muberry pyralid was multiplied as virus masses in several portion of the nuclei of the midgut cell.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.2 no.2
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• pp.69-77
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• 1997

A 12-cm long sediment core was collected from a station in Lake Shihwa where high salinity-anoxic deep water is isolated from low salinity-oxic surface water by a strong halocline barrier. Unprecedented concentrations of porewater ammonia and lead are encountered: at 9 cm sediment depth ammonia builds up to 1420 ${\mu}M$ and at 3 cm lead to 1348 nM. As they are stable in anoxic condition, high concentrations of ammonia and lead suggest a development of notorious anoxic condition in the benthic environment of the lake. The degree of pollution of the deep water is likely to be directly proportional to the magnitude of benthic flux, because the deep water is isolated from the surface water by the halocline. Apparent coincidence of the ammonia residence time in the deep water with the elapsing time after the completion of the artificial lake construction, as about three years, suggests that the deep water pollution is being progressed entirely by benthic flux at least with respect to ammonia. The residence time for lead is such a short 20 days that it suggests a rapid return of the bottom water lead, which is originated from porewater by benthic flux, back to sediments probably as metal sulfide phases. The speculation on the return of lead as sulfide phases is likely to be supported by high concentration of hydrogen sulfide in the deep water and by high sinking rate of non-organic particles in Lake Shihwa.

• Applied Chemistry for Engineering
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• v.24 no.6
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• pp.656-662
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• 2013

The iron oxide ($Fe_3O_4$) particles in the coolant of the secondary system of a nuclear power plant reduce the heat transfer performance or induce corrosion on the surface of the heat transfer tube. To prevent these problems, we conducted a study to improve the dispersion stability of iron oxide using polymeric dispersant injection in simulated secondary system water. The three kinds of anionic polymers containing carboxyl groups were selected. The dispersion characteristics of the iron oxide particles with the polymeric dispersants were evaluated by performing a settling test and measuring the transmission, the zeta potential, and the hydrodynamic particle size of the colloid solutions. Polymeric dispersants had a significant impact on the iron oxide dispersion stability in an aqueous solution. While the dispersant injection tended to improve the dispersion stability, the dispersion stability of iron oxide did not increase linearly with an increase in the dispersant concentration. This non-linearity is due to the agglomerations between the iron oxide particles above a critical dispersant concentration. The effect of the dispersant on the dispersion stability improvement was significant when the dispersant concentration ratio (ppm, dispersant/magnetite) was in the range of 0.1 to 0.01. This suggests that the optimization of dispersant concentration is required to maximize the iron oxide removal effect with the dispersant injection considering the applied environments, the iron oxide concentration and the concentration ratio of dispersant to iron oxide.

• Journal of the Korean Ceramic Society
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• v.39 no.12
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• pp.1143-1148
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• 2002

Precipitated calcium carbonate is one of the most versatile mineral fillers and is consumed in an wide range of products including paper, paint, plastics, rubber, textiles, sealants, adhesives and printing ink and can be produced by several methods. Calcium carbonate has three isomorphism; vaterite, aragonite and calcite, with numerous variations of morphology in the natural mineral or organism. Formation process of vaterite in the reaction of system $Ca(OH)_2-CH_3OH-H_2O-CO_2$ were investigated by measuring the electrical conductivity, $Ca^{2+}$ ion concentration, pH in the slurries and by means of X-ray diffraction and electron microscopic observation. It was clearly established that the reaction temperature is important variable in the carbonation process; in general over 50${\circ}C$, the vaterite was precipitated with the calcite and aragonite. SEM and XRD observations revealed that the vaterite formation could be prepared the temperature range of 40 to 50${\circ}C$ and mean size of particles in this range is controlled from 0.5 to 0.8 ${\mu}m$.

• Korean Journal of Microbiology
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• v.30 no.5
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• pp.383-390
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• 1992

In the periods of July 31 to August 10. 1988 and March 9 to 13. 1989. sediment samples were collected from the South Sea stations (010] to 092]) located in the area from $N 32^{\circ}$/30' to $34^{\circ}$/30', of latitude and from E $123^{\circ}$ 30' to $128^{\circ}$30' of longitude. These samples were analyzed for the number of total heterotrophic bacteria and extracellular digesting enzyme activities. In the 1989 spring period the number of heterotrophic bacteria in the sediment surface layer was increased more than 100 times at the maximum compared to that in the 1988 summer period. The proportion of fresh water bacteria to total heterotrophic bacteria was also higher in the spring period than the summer period. The extracellular digesting enzyme activities were higher in spring season than summer. Although the water content of sediment in the spring period was lower than that the summer period. the ash weight indicating organic material content was higher. These results means that the diameters of sediment particles were larger in spring than summer but the input of organic material into the sediment was greater. Based on these results bacterial distributions in the sediment layer of South Sea depend greatly on the season due to the effect of fresh water. During the spring season plankton could grow extensively owing to the inorganic nutrients input by the vertical mixing in the water column, then be precipitated into the sediment. Organic nutrients supplied from enzymatic degradation of polymeric particle from plankton can increase the bacterial number, too.

• Journal of Korea Water Resources Association
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• v.47 no.5
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• pp.483-490
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• 2014

The design procedures for a biological reactor and a secondary settling tank (SST) of an activated sludge system are based on the steady state design method (Ekama et al., 1986; WRC, 1984) and the 1-D flux theory design method (Ekama et al., 1997), respectively. This study combined both of the design procedures, to determine the optimum sludge concentration in the reactor and the best design with the lowest cost. The best design of the reactor volume and the SST diameter at the optimum sludge concentration were specified with varying wastewater and sludge characteristics, temperature, sludge retention time (SRT) and peak flow rate. The effects of the influent wastewater characteristics, such as substrate concentration and unbiodegradable particulate fraction, were found to be considerable, but the effect of unbiodegradable soluble fraction was to be negligible. The effects of sludge settling characteristics, were also significant. SRT, as an operating parameter, was found to be an important factor for determining the optimum sludge concentration. However, the effect of temperature was found to be small. Furthermore, for designing a large scale wastewater treatment plant, the number of reactors or SSTs could be estimated, by dividing the total reactor volume or SST area. The new combined design procedure, proposed in this research, will be able to allow engineers to provide the best design of an activated sludge system with the lowest cost.

• The Journal of Engineering Geology
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• v.16 no.4 s.50
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• pp.403-409
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• 2006

This study was performed to assess the clay impact on alga growth which was a primary producer, in view of food chain in ecosystem. As clay minerals caused turbidity, a low sedimentation, high adsorption capacity with organic matter, adsorption - desorption effect with ionic chemicals, clay minerals were supposed to have a significant effect on the aquatic system. In study we tried to turn out NOAEL (No-observed-adverse-effect-level) of clay materials on the algae growth inhibition using such as kaolinite, sericite and montmorillonite. This study was indicated. (1) In both of kaolinite and sericite, the $72hr-EC_{50}$ of them shows 2,752 mg/L and 2,775 mg/L, respectively. (2) On the other hand, in the case of montmorillonite, the $72hr-EC_{50}$ is not shown a significant difference to that of control samples. (3) It can be explained that is also a very important parameter in an alga growth. Because an alga growth was increased when the permeability of W visible radiation was increased in all clay cases. (4) It is demonstrated alga growth was affected by the characteristics of clay materials. Hence we can assess the $\ulcorner$water environmental risk assessment caused clay materials$\lrcorner$ using the alga growth inhibition level indirectly.

• The Journal of Engineering Research
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• v.5 no.1
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• pp.73-87
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• 2004

The synthesis and crystallization of amorphous calcium carbonate($CaCO_3$.$nH_2 O$) obtained from gas-liquid reaction between aqueous solution of calcium hydroxide and carbon dioxide at 15~$50^{\circ}C$ are investigated by electrical conductometry, XRD and TEM. The results are as follows: The initial reaction products prior to the formation of precipitated calcium carbonate is amorphous calcium carbonate. The electrical conductivity values in the slurry are decreased during the formation of amorphous calcium carbonate which covers particle surface of calcium hydroxide and retard the dissolution of calcium hydroxide into the solution. that amorphous calcium carbonate is unstable in the aqueous solution and crystallizes finally to calcite by the through-solution reaction. While amorphous calcium carbonate crystallizes into chain-like calcite, the conductivity values are recovered rapidly and the apparent viscosity of slurry containing higher concentration of calcium hydroxide increase. At below pH 9.5, chain-like calcite separates into individual particles to form precipitated calcium carbonate. The formation and synthetic temperature range of amorphous calcium carbonate is most suitable a primary decreasing step(a-step) at $15^{\circ}C$ in the electrical conductometry.