• Proceedings of the Korea Water Resources Association Conference
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• 2005.05b
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• pp.1378-1382
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• 2005

여름철 집중강우시 유입되는 고탁수층은 저수지의 밀도성층으로 인하여 표수층 하부에 위치하며, 이를 적기에 배제하지 않을 경우에는 수평방향의 확산현상과 연직방향의 전도현상으로 인해 저수지 전역에 분포하게 되어, 탁수현상의 장기화를 유발한다. 이와 같은 탁수장기화에 대한 저수지내 대책의 하나로서 홍수유입후 탁도가 높은 물을 단기간동안 방류하고, 갈수기에는 탁도가 낮은 물을 방류하는 선택취수 기법을 적용할 수 있다. 임하댐의 경우, 2004년 태풍 '디앤무'와 태풍 '메기'로 인해 발생한 탁수를 선택취수를 통하여 조기에 배제함으로써 호내탁도를 저감시킨 바 있다. 그러나 이와 같은 고탁수 우선배제 기법은 반드시 하류하천의 영향범위를 사전에 분석검토하고, 하류하천의 수질현황을 고려한 합리적인 운영방안이 제시되어야 한다. 2004년 태풍 '디앤무' 발생직후의 댐방수로에서 170 NTU의 고탁수를 방류한 경우, 유하거리 250 km인 지점까지 30 NTU이상 유지된 바 있으며, 태풍 '메기'에 의한 고탁수 유입시, 임하댐 방류수 157 NTU, 안동댐 방류수 37 NTU인 경우에 임하댐 하류 113 km인 구미 선산 취수장까지 63 NTU의 탁도가 유지된 바 있다. 현재 임하댐의 경우, 하류하천으로의 방류수 수질을 모니터링할 수 있는 자동수질측정시스템이 발전취수탑 전면 1개소, 조정지댐 1개소에 설치되어 있다. 본 연구에서는 자동수질측정시스템과 연계하여 수질모형을 통하여 임하댐 하류하천인 낙동강 본류의 탁도관리시스템을 구축하고자 하였다. 환경부의 수질측정망 자료를 통하여 최근 3년간의 부유사농도의 변화양상을 분석하였으며, 태풍 직후의 낙동강 주요지점별 탁도측정자료를 이용하여 임하댐 고탁도방류에 의한 영향범위를 분석하였다. 또한 하천수질모형을 이용하여 탁수예측방법에 대하여 검토하였고, 이를 이용한 탁도관리시스템 구축을 위한 기본 방향을 제시하고자 한다.함께, 2단계에 (주)웹솔루스에서 자체적으로 설치 운영하고 있는 2개소의 하수관거 모니터링 관측시설, 그리고 안양시에서 운영하고 있는 5개소의 강우관측소와 7개소의 수위관측소를 모두 통합하여 실시간 자료를 제공하고 있다. 수위자료는 10분단위의 텍스트정보와 그래프형태로 지원되며, 검색기간 설정을 통해 원하는 기간내의 자료를 선별, 검색할 수 있다.. 또한 이와 같은 기초적인 정보를 바탕으로 하류하천의 탁수 피해를 최소화할 수 있는 선택취수탑의 운영방안을 수립할 수 있다 본 연구에서는 이를 위해 선택취수탑 주위의 성층흐름을 기존의 실험자료와 수치해석을 통하여 분석하였고, 온도성층구조나 취수구의 위치변화에 따른 방류수 수질특성을 조사하였다.쇄파대(artifical reef)와 같은 완충지대를 갖는 호안을 축조함으로써 월파량을 감소시키는 대안으로 제시하고자 한다. 본 연구 수행을 통해 태풍 내습시 발생 가능한 자연재해에 대한 사전 방지를 목적으로 태풍피해의 원인을 제시하고 이를 해결하여 현재의 방재대책이 항구적인 방재대책으로 전환될 수 있는 방안 마련의 기초 자료로 활용되기를 기대한다., L-arabinose, 및 D-galactose; 제3차(第三次) 가수분해물(加水分解物)(C)에서 L-rhamnose, D-xylose, L-arabinose 및 D-galactose, 비가수분해물(非加水分解物)(C')에서 D-xylose와 D-galactose를 검출(檢出)하였다. (4) 구성당(構成糖)의 형태(形態)와 구조(構造)를 밝히기 위(爲)해 polysaccharide C에 대한 periodate산화(酸化) 실험(實驗)을 하여 $C_5H_8O_4$당(當) periodate의 소비(消費)와 formic acid의 생성량(生成量)을 측정(測定)하였는데 periodate의 소비량(消費量)은 1.23 mole, formic acid의 생성량(生成量)

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.3
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• pp.1151-1156
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• 2011

Leveraged buyouts (LBO) means the acquisition of a company using bonds and loans. There are the prolific volumes of LBO transactions in the international M&A markets, and its influence to the financial market is increasingly huge. However, there are very few LBO transaction in the domestic M&A market and there are also few researches in this field due to the private nature of LBO transactions. Once a company is privatized through a LBO transaction, it is not so long before it is relisted on the stock exchange or it is resold to a third-party investor. In order to repay the borrowed money, an LBO investor may decide to end a company's private status through an exit via an initial public offering (IPO) or a takeover. In this paper, we expand Kaplan's study on the organizational status of post leveraged buyout (LBO) transaction. We find that there is a significant change starting 1986. Most notably, fewer LBOs remain private, the median holding period of the LBO was cut in half to 3.2 years and of those that exit, IPO exits had significantly shorter holding periods. Regression analysis shows that good market conditions lengthen the holding period of a LBO investment whereas the size of the transaction shortens it.

• Tunnel and Underground Space
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• v.12 no.1
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• pp.52-69
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• 2002

The WIPP (Waste Isolation Pilot Plant), located 42km east of Carlsbad, New Mexico (NM), in bedded salt 655m below the surface, is a mined repository constructed by the US DOE for the permanent disposal of transuranic (TRU) wastes generated by activities related to defence of the US since 1970. Its historical disposal operation began in March 1999 following receipt of a final permit from the State of NM after a positive certification decision for the WIPP was issued by the EPA in 1998, as the first licensed facility in the US for the deep geologic disposal of radioactive wastes. The CCA (Compliance Certification Application) for the WIPP that the DOE submitted to the EPA in 1966 was supported by an extensive performance assessment (PA) carried out by Sandia National Laboratories (SNL), with so-called 1996 PA. Even though such PA methodologies could be greatly different from the way we consider for HLW disposal in Korea largely due to quite different geologic formations in which repository are likely to be located, a review on lots of works done through the WIPP PA studies could be the most important lessons that we can learn from in view of current situation in Korea where an initial phase of conceptual studies on HLW disposal has been just started. The objective of this art report is an overview of the methodology used in the recent WIPP PA to support the US DOE WIPP CCA and some relevant results completed by SNL.

• Economic and Environmental Geology
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• v.42 no.6
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• pp.635-643
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• 2009

In this paper, a Quaternary fault is described, which is developed in the mid-eastern part of Ulsan Fault Zone, near the southern Gaegok-ri, Oedong-eub, Gyeongju, Korea. The Gaegok 6 fault is developed along the contact between Early Tertiary granite and Quaternary gravel deposit overlying unconformably the granite. The fault strikes $N02^{\circ}{\sim}22^{\circ}E$ and dips $45^{\circ}{\sim}80^{\circ}$ to the west. This fault has a 30~50 cm wide cataclastic shear zone with gouge zone, mixed with Quaternary sediments and fault breccia of granite. In the main Quaternary fault plane, the orientation of striation is $17^{\circ}$, $356^{\circ}$, indicating a dextral strike-slip faulting with some normal component. There is another striation ($78^{\circ}$, $278^{\circ}$ and $43^{\circ}$, $270^{\circ}$) with reverse-slip sense, developed on the subsidiary plane which cuts the main Quaternary fault plane. In brief, the fault has been developed between the granite in the western part and the Quaternary gravel deposit in the eastern part. The western block of fault is uplifted. The striations and movement senses of faults indicate multiple compressional stages in this region. The fault has a similar orientation, westward dipping geometric pattern, and reverse sensed kinematic pattern with Gaegok 1 fault developed in the north. Thus, the Gaegok 6 fault is probably a southern extension of Gaegok 1 fault.

• The Journal of Engineering Geology
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• v.25 no.2
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• pp.201-213
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• 2015

Site effects resulting in the amplification of earthquake ground motion are strongly influenced not only by the subsurface soil conditions and structure, but also by the surface topography. Yet, over the last several decades, most studies of site-specific seismic responses in Korea have focused primarily on the seismic amplification associated with geologic and soil conditions. For example, the effects of local geology are now well established and have been incorporated into current Korean seismic design codes, whereas topographic effects have not been considered. To help address this shortcoming, two-dimensional (2D) seismic site response analyses, using finite element (FE) ground modeling with three different slope angles, were performed in order to assess the site effects of surface topography. We then compared our results, specifically peak ground acceleration (PGA) and acceleration response spectrum, to those of one-dimensional (1D) FE model analyses conducted alongside our study. Throughout much of the upper slope region, PGAs and spectral accelerations are larger in the 2D analyses than in the 1D analyses as a result of the topographic effect.

• Journal of Korean Tunnelling and Underground Space Association
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• v.20 no.3
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• pp.575-592
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• 2018

Tunnelling is getting more important solutions for problems induced by the growth population in urban areas. Many studies on tunnelling below existing structure are carried out by many researchers. In general, however, ground water condition is ignored for most of researches using laboratory model test, so far. In case of ground behavior, error can occur if the result of effective stress related to hydraulic condition can't be taken into considerations. In this study, therefore, laboratory model test and the close range photogrammetry were conducted to investigate behaviour of ground and shallow foundation using newly device drainage system which is available to express the ground water condition. Also, numerical analysis was carried out to compare to results from the laboratory model test, and was performed with two methods, one is plastic and the other one is fully coupled analysis. Results from those two methods were compared to that of the laboratory model test.

• Journal of Korean Society of Environmental Engineers
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• v.38 no.5
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• pp.228-235
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• 2016

Nitrite accumulation is essential for constructing an anammox process. As the pH in the reactor exerts a complicated and strong influence on the reaction rate, we investigated its effects upon treatment of an ammonic wastewater (2,000 mgN/L) through modeling and experiment. The modeling results indicated that the reaction stability is strongly affected by pH, which results in a severe reduction of the 'stable region' of operation under alkaline environments. On a coordinate of the total ammonia nitrogen (TAN) concentration vs. pH, the maximal stable reaction rates and the maximal nitrite accumulation potentials could be found on the 'stability ridge' that separates the stable region from the unstable region. We achieved a stable and high ammonia oxidation rate (${\sim}6kgN/m^3-d$) with a nitrite accumulation ratio of ~99% when operated near the 'stability ridge'. The optimum pH that can be observed in experiments varies with the TAN concentrations utilized, although the intrinsic optimum pH is fixed. The direction of change is that the optimum operational pH falls as the TAN concentration increases, which is in excellent accordance with the observations in the literature. The optimum operational pH for 95% nitritation was predicted to be ~8.0, whereas it was ~7.2 for 55% partial nitritation to produce an anammox feed in our experimental conditions.

• Korean Journal of Agricultural and Forest Meteorology
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• v.7 no.1
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• pp.45-50
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• 2005

This study was conducted to measure and understand the exchange of CO₂ and water in a rice canopy. Eddy covariance system was installed on a 10m tower along with other meteorological instruments. CO₂ flux and surface energy balance were measured throughout the whole growing season in 2003 over a typical paddy field in Icheon, Korea. During the early growth stage in May and June, most of net radiation was partitioned to latent heat flux with daytime Bowen ratio of 0.3 to 0.7. Evapotranspiration (i.e., daily integrated latent heat flux) typically ranged from 3 to 4 mm d/sup -1/, with even higher rates on sunny days. Daily integrated net ecosystem exchange (NEE) of CO₂ increased with increasing solar radiation and leaf area index (LAI). The NEE was especially high during the stages of young panicle formation and heading. On 1 June 2003, when the rice field was flooded, it was a weak sink of atmospheric CO₂ with an uptake rate of 9.1 gm/sup -2/d/sup -1/. Despite frequent rainy and cloudy conditions in summer, maximum NEE of 36.2 gm/sup -2/d/sup -1/ occurred on 31 July prior to heading stage. As rice crop senesced after early September, the NEE decreased.

• Korean Journal of Agricultural and Forest Meteorology
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• v.13 no.2
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• pp.48-55
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• 2011

Solar radiation components reflected by the sea surface ($R_{ss}\uparrow$) are additional energy sources comprising the solar radiation regime. Previous studies, based on observational approaches, indicated that $R_{ss}\uparrow$ is an available climatological resource. However, an estimation process for $R_{ss}\uparrow$ has not been established. In this case study over Jeju Island in South Korea, we applied a new estimation process to solar radiation modeling and discussed the spatial distribution of $R_{ss}\uparrow$ and its seasonal variation. Our results showed that the illuminated area and the intensity of $R_{ss}\uparrow$ became greatest at the winter solstice and least at the summer solstice. We estimated the illuminated area of $R_{ss}\uparrow$ as it expanded over the southern slope of Jeju Island. At the winter solstice, on a daily basis, the area and intensity of illumination by $R_{ss}\uparrow$ were $182.3km^2$ and $0.41\;MJ\;m^{-2}\;day\;{-1}$, respectively. Comparing the daily accumulative and instantaneous values of $R_{ss}\uparrow$ intensity, the difference was about 20 times greater in daily cases than in instantaneous cases. On the other hand, for instantaneous values, the $R_{ss}\uparrow$ intensity accounted for up to 33% of the three components, i.e., direct, diffuse and reflected radiation in winter solstice. In addition, it was estimated that the sea surface reflectance depended on the wind speed. Therefore, in a practical use of this revised model, wind conditions should be considered as a critical factor in estimating $R_{ss}\uparrow$.

• The Korean Journal of Pesticide Science
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• v.4 no.4
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• pp.35-39
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• 2000

In order to develop the indicators of environmental impact of pesticide, its actual usage in paddy rice was surveyed, and usage trends of individual pesticides were evaluated. The tendency of pesticide use indicated insecticide 43%, herbicide 29%, fungicide 27% and top ranking item in insecticide, herbicide and fungicide was carbofuran, molinate + pyrazosulfuran-ethyl, IBP. The usage statistics of formulation types showed GR>DP>WP>EC>FG>SP. Pesticide usage(a.i.) per hectare was 7.13kg and total usage for paddy rice was estimated at 8,387 M/T. In the result of comparison of fact-usage with pesticide consumption reported in 1998, the fitness was 94.7% for fungicide, 84.3% for insecticide, 77.8% for herbicide. The result of monitoring pesticide residue of unpolished-rice sampled from farm house of survey indicated 0.14 ppm(BPMC), 0.16 ppm(Isoprocarb), 0.17 ppm(Isoprothiolane). In case of rice straw, the residue level was 0.27 ppm(Isoprothiolane), 0.28 ppm(IBP), 0.39 ppm(Carbofuran). The residue levels of pesticides were below MRLs.