• Resources Recycling
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• 제2권4호
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• pp.1-9
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• 1993

A study on the recovery of nitric and hydrofluoric acids is carried out with pulsed column extractor in order to the industrial application of this process. Firstly, from the continuous experiments about the recovery of acids using domestic stainelss steel pickling solution, it is found out that the free nitric and hydrofluoric acids are only extracted by 70% TBP and the heaby metals such as Fe, Cr and Ni are not extracted. The effectiveness of extraction and stripping generally improves as the pulse velocity(product of amplitude and frequency) is increased, optimum performance typically occuring slightly below an amplitude-frequency product which results in flooding the column because of excessive emulsification. When the pickling solution is treated by 70% TBP at a phase ratio of A/O=1/2 in the extraction and by distilled water at a phase ratio of O/A=1 in the stripping, the concentration of refined acides are 102g/$\ulcorner$ $HNO_3$and 8.8g/$\ulcorner$ HF, respectively and the recovery of $HNO_3$and HF are 90.7% and 75.2%, respectively.

• Journal of the Korean Society for information Management
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• 제18권4호
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• pp.103-125
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• 2001

The study is to analyze correlation between 12 factors related to the collection development and the collection size by the type of materials of university libraries in Korea. The results of this study are summarized as follows. The result of the correlation analysis: the number of volumes and serials titles showed the positive correlation, except 1∼2 factors by the founder, but there was no correlation between most of factors and the number of nonbok materials. And as the result of Spearman correlation analysis, the rank between correlation coefficients of the national university libraries and those of the private ones showed the coincidence of 61% only in the case of serials. The results of the bring out the significant differences only in total volumes. By the type of materials, between total volumes and added ones, most of factors revealed the higher correlation with total volumes; between added volumes and serial titles, 2∼3 factors brought out the higher correlation with serial titles; between total volumes and serial titles, most of factors showed the higher correlation with total volumes.

• Proceedings of the Korea Water Resources Association Conference
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• 한국수자원학회 2011년도 학술발표회
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• pp.233-233
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• 2011

필요한 수자원을 추가확보하기 위한 댐 건설이 갈수록 어려워짐에 따라 이미 건설된 댐을 최대한 활용하는 과학적 저수지운영 방안이 필요하다. 또한 댐운영자가 쉽게 실무에 적용할 수 있는 방법이어야 한다. 본 연구의 목적은 댐관리자가 이해하기 쉽고 사용하기 쉬운 장기 저수지운영 방안을 개발하고자 하는 것이다. 수위구간별 저수지운영을 위한 운영률을 구성하고 이에 따른 순단위 저수지운영 모형을 구축하였다. 다변량 추계학적 모의발생기법을 사용하여 댐 유입량을 모의 발생하였다. 저수지운영의 수위구간을 결정하기 위한 최적화 방법으로 메타휴리스틱 방법으로 차원변화 탐색기법을 선정하였다. 안동댐의 단독운영을 위한 수위구간별 저수지운영률을 도출하여 저수지 모의운영을 수행하고 기존의 운영실적과 모의결과를 저수지운영 평가기준에 따라 비교하여 평가하였다. 안동댐의 단독운영 결과 모의된 저수위는 실적 저수위보다 전반적으로 높게 유지되었고, 모의 발전량이 실적 발전량보다 평균적으로 높음을 볼 수 있었다. 안동댐의 실적 발전량 평균값은 124.81 GWh이며, 모의결과의 발전량은 131.01 GWh이었다. 모의 발전량이 전반적으로 높은 이유는 방류량이 적은 상황에서 저수위를 높게 유지하여 발전효율을 높게 한 것이 주된 이유라고 사료된다. 안동댐의 실적과 모의 결과를 3 가지 저수지운영 평가기준으로 평가한 결과, 실패한 횟수는 실적이 554 회, 모의결과는 426 회이었다. 또한 2 순 연속하여 실패가 발생한 횟수는 각각 71회, 48 회이었고, 최대 연속 실패는 각각 52 순, 51 순이었다. 또한 총운영 기간에 대한 성공 횟수의 비율을 나타내는 신뢰도는 실적은 0.53, 모의된 결과는 0.64로 약 9 %의 차이를 보였다. 취약도는 실적이 $12.69\times10^6\;m^3$, 모의된 결과가 $5.14\times10^6\;m^3$로 $7.55\times10^6\;m^3$의 차이를 보였다. 회복도는 실적이 0.21, 모의 결과가 0.13으로 모의결과가 0.08 낮은 것으로 나타났다. 도출된 장기 저수지운영률을 안동댐의 단독운영에 적용한 결과 실적보다 본 연구에서 개발한 방법론에 의한 모의운영이 공급량, 발전량, 저수지 운영평가 통계량에서 나은 결과를 보였다.

• The Korean Journal of Applied Statistics
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• 제31권1호
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• pp.139-153
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• 2018

This paper investigates solar power forecasting based on several time series models. First, we consider weather variables that influence forecasting procedures as well as compare forecasting accuracies between time series models such as ARIMAX, Holt-Winters and Artificial Neural Network (ANN) models. The results show that ten models forecasting 24hour data have better performance than single models for 24 hours.

• Journal of Korea Water Resources Association
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• 제30권4호
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• pp.401-409
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• 1997

This study aims to predict the bed elevation change of river and reservoir by compound water model, two-dimensional jet model and one-dimensional density current model, assuming that the river has a single channel and the reservoir has multiple channels. In numerical model, discharge and water level changes is obtained by flow continuity equation and flow momentum equation through double-sweep method, and then applied to sediment continuity equation to predict the scour and deposit of channel bed. The span ranged from the Bosung Dam to Mundueok Bridge at the upstream of Juam Dam, which is approximately 31km long (13km of river and 18km of reservoir), is taken as survey area.

• Economic and Environmental Geology
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• 제36권3호
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• pp.159-170
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• 2003

Heavy metals are extracted from Chonju stream sediment, roadside soils and sediments along Honam expressway, soils and tailings from mining area using three different methods (partial extraction in Standard Method, partial extraction method with maintaining 0.1 N of extraction solution and Sequential Extraction Method). In samples having buffer capacity against acid, pH 1 (0.1 N HCl) of extraction solution can not be maintained and pH of extraction solution increases up to 8.0 when partial extraction in Standard Method is used. The averages and ranges of HPE(heavy metals extracted using partial extraction in Standard Method)/HPEM(heavy metals extracted using partial extraction method with maintaining 0.1 N of extraction solution) values are 0.479 and 0.145~0.929 for Cd, 0.534 and 0.078~0.928 for Zn, 0.432 and 0.041~0.992 for Mn, 0.359 and 0.011~0.874 for Cu, 0.150 and 0.018~0.530 for Cr, 0.219 and 0.003~0.853 for Pb, and 0.088 and 1.73${\times}$10$^{-5}$~0.303 for Fe. These data indicate that the difference between HPE and HPEM is large in the order of Fe, Cr, Pb, Cu, Mn, Cd and Zn. The amounts of heavy metals extracted decreases in the follow order; Sum III(sum of fraction I, II, III in sequential extraction)>HPEM>Sum III (sum of fraction I and II)>HPE for Zn, Cd and Mn and Sum III>HPEM>HPE for Cr and Fe. In the case Cr, Sum II is lower than HPEM and higher than HPE. In case of Cu, extracted heavy metals is large in the order Sum IV>HPEM>Sum III HPE. HPE/HPEM value decreases with increasing the amount of HCl used for maintaining 0.1 N of extraction solution. For samples with high buffer capacity, HPE/HPEM value in all elements is lower than 0.2. On the other hand, for samples with low buffer capacity, HPE/HPEM value are over 0.2 and many samples have values higher than 0.6 for Zn, Cd Mn and Cu due to the small difference between Sum II and Sum III, and relatively higher mobility. However, for Fe and Cr, HPE/HPEM value is below 0.2 even for samples with low buffer capacity due to their low mobility and big difference between Sum II and Sum III. This study indicates that the partial extraction method in Korean Standard Method of soil is not suitable for an assessment of soil contamination in area where buffer capacity of soil can be decreased or lost because of a long term exposure to environmental damage such as acidic rain.

• Journal of Wetlands Research
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• 제19권1호
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• pp.132-143
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• 2017

It is essential to obtain periodic sediment discharge data in a river in order to minimize problems that may arise from the erosion, transport, and deposition of sediment. However, it is difficult to estimate sediment discharge by the sediment discharge measurement plan in Korea at present, and empirical fomulas or numerical models are used to replace them. This paper has applied the K-DRUM model, a grid-based rainfall-runoff-sediment model, to estimate sediment discharge and ensure the continuity of the data in the watershed. Discharge and sediment load in 17 watersheds were estimated and the applicability of the model was analyzed through comparisons with measured data. For quantitative evaluation, NSE, PBIAS and RSR items were used, and discharge results reflected the tendency of rainfall and showed high statistical value. In case of sediment discharge, the soil erosion process of the watershed is physically well reflected. When the calibration was performed using the measure data, the applicability seems to be excellent in estimating the continuous sediment discharge data in the real watershed.

• Journal of the Korea Organic Resources Recycling Association
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• 제16권2호
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• pp.47-56
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• 2008

The objective of this research is to evaluate the optimum recycling methods for the sewage sludge cakes at different microwave power-settings and for different periods of time. The dehydrated sewage sludge cakes used in this study was obtained from N wastewater treatment plan in the P City. The beginning drying processes were carried out in a microwave oven with 2,450 MHz frequency and power ranges of 1kW to 4 kW. The continuous conveyer drying system was also operated with 2,450 MHz frequency and power setting, ranging from of 1 kW to 6 kW. Initial moisture content of the sewage cake is 78~80%, and the moisture content decreased rapidly up to 0.2~2(wt%) within short periods due to breaking the cell walls. This study is also conducted to evaluate the characteristics of sewage sludge cakes with respect to important physical parameters effect on the thermal kinetics for evaporation water in the sludge which are operation times, moisture contents, drying rates, input amounts, flow rates and calorific values. It takes 60 minutes and 120 minutes to reach the critical moisture contents with power setting of 4 kW for 3kg/min and 6kg/min of the flow rates respectively. It takes 120 minutes and 110 minutes to reach the critical moisture contents with flow rates of 2.5 cm/min and sludge input of 6kg/min for the power settings of 4 kW and 6 kW respectively. The most effective value of the power for drying the sludge is 4 kW. Operation with 6kg/min and 4kW on 2cm of the sludge thickness can be effectively and inexpensively to reach the critical moisture contents, when you compare 2cm of the sludge thickness with 1cm and 3cm of the sludge thickness.

• Communications for Statistical Applications and Methods
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• 제15권6호
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• pp.977-991
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• 2008

This study is about the k-nearest neighbor-based approach for the estimation of mutual information when the type of target variable is categorical and continuous. The results of Monte-Carlo simulation and experiments with real-world data show that k=1 is preferable. In practical application with real world data, our study shows that jittering and bootstrapping is needed.

• Proceedings of the Korea Society for Simulation Conference
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• 한국시뮬레이션학회 2002년도 추계학술대회 논문집
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• pp.125-130
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• 2002

본 연구는 DEVS를 기반으로 개발된 교통류 시뮬레이션 시스템인 $\ulcorner$I$^3$D$^2$ 교통류 시뮬레이션 시스템$\lrcorner$(이하 I$^3$D$^2$)의 검증을 그 목적으로 한다. I$^3$D$^2$는 본 연구진이 DEVS를 기반으로 개발한 범용 시뮬레이션 도구로써, 이미 서울시 강남 신호교차로와 내부순환로를 대상으로 하여 개발된 내용을 발표한 바 있다. I$^3$D$^2$는 헌재 단속류에서의 최적신호 생성 및 대기행렬 예측 문제, 그리고 연속류 시설의 용량 산정 문제등을 시뮬레이션 할 수 있다. 하지만 아직 문헌자료나 현장 데이터를 토대로 한 충분한 검증이 수행되지 못한 문제가 있다. 따라서 본 연구에서는 문헌자료를 토대로, I$^3$D$^2$를 검증한다. 이를 위하여 고속도로 또는 도시고속도로와 같은 연속 교통류의 대표적인 효과척도인 $\ulcorner$교통량 - 밀도 - 평균주행속도 (시간)$\lrcorner$ 간의 상관관계를 이용하여 미국 HCM과 우리나라의 도로용량편람에 정의되어 있는 기준을 토대로 I$^3$D$^2$ 검증을 수행하였다. 모델링은 서울시 올림픽대로의 양화대교 - 성산대교 - 가양대교 구간을 대상으로 했으며, 검증은 교통량에 따라 크게 3가지 교통류 상태(random, intermediate, constant)를 기준으로 시뮬레이션이 각각의 교통상태에서 예측한 평균주행시간의 정확도를 측정하면서 수행하였다. 검증 결과 random 상태에서는 문헌자료에 부합되는 예측결과를 보여주었으나, intermediate와 constant 상태에서는 문헌보다 다소 낮은 속도를 보여주었다 이러한 속도차는 추후 현장 데이터를 수집하여 보다 실질적인 검증을 통하여 조정되어야 할 것으로 판단된다.