• 한국수자원학회논문집
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• 제36권6호
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• pp.1097-1107
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• 2003

개념적 집중형 일 유출모형인 DAWAST모형을 선정하여 용수수요를 고려할 수 있는 가능성을 검토하였다. 기존 모형에 의한 모의 유량을 자연유량으로 보았고, 농업용수, 생활용수, 공업용수 등 회귀수량을 더한 값을 하천유량으로 가정하였다. 농업용수의 수요량은 회귀수량이 논으로부터만 발생하는 것으로 보아 논 용수량만을 고려하였으며, 수정 Penman공식에 의한 증발산량, 침투량, 재배관리수량, 유효우량 등을 고려한 일별 감수심에 의해 일별로 계산하였다. 생활용수, 공업용수 수요량은 일 평균값에 월별 변동계수를 고려하여 일별로 계산하였다. 신뢰도가 높은 대청댐 운영실적의 유입량 자료를 이용하여 용수수요를 고려한 DAWAST 모형의 적용성을 평가하였다. 농업용수의 회귀율은 35%, 생공용수의 회귀율은 65% 적용하였으며, 1983년∼2001년 연평균하여 강우량 1184.6 mm 관측 유입량 667.3 mm 모의 유입량 652.6 mm 로 용수수요를 고려하지 않은 경우의 모의 유입량 606.8 mm에 비해 45.8 mm 가 높게 나타났으며, 모의/관측 유입량 비율도 90.9 % 에서 97.8% 로 개선되는 결과를 얻었다.

• 한국농공학회:학술대회논문집
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• 한국농공학회 2003년도 학술발표논문집
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• pp.503-506
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• 2003

The DAWAST model was originally developed to consider daily variation in the unsaturated soil water storage and it is a conceptual lumped model. Return flows from agricultural, domestic and industrial water were included to the original result of model simulation to calibrate model parameter. Daily inflow to the Daechung multipurpose dam was applied to verify the DAWAST model considered return flows. Simulation results were comparable to the inflows of dam operation reasonably.

• 한국경영과학회지
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• 제11권1호
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• pp.12-23
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• 1986

The minimum attractive rate of return (MARR) has been used for many years as a decision criterion in engineering economic analysis. Typically, inflation has been either ignored in such studies or considered by adjusting each of the individual cash flows associated with a project for inflation, frequently a lengthy process. This research investigates a new decision criterion for economic analysis, the comparative rate of return (CRR). The CRR is defined to be the minimum rate of return earned on uninflated cash flows of proposed expenditures is simplified, since the analysis can be performed on the uninflated cash flows. The research presents a derivation of the CRR and investigates its relationships to the MARR, inflation rate project cash flows and project life.

• 한국농공학회논문집
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• 제46권7호
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• pp.71-80
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• 2004

A system for estimating daily paddy irrigation water requirements was developed to simulate daily stream flows that reflect various upstream and downstream return flows from river basin. Evapotranspiration in paddy fields was estimated using the modified Penman equation. Daily irrigation water requirements of paddy fields were calculated by multiplying the paddy area and the daily decrease in ponding depth. The system was constructed almost completely using images, grids, etc. in Visual Basic 6.0. The developed model was verified in the Damyang dam, and was used to estimate daily paddy irrigation water requirements at 12 small watersheds in Geum river basin for 20 years, from 1983 to 2002, covering paddy field areas of $3,332\~26,422$ ha. The results on the runoff analysis on the inflow to the Daecheong multi-purpose dam with various return flows were satisfactory. They were reasonable compared to the scenario where return flows were not considered.

• 한국농공학회지
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• 제29권3호
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• pp.138-144
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• 1987

This study was conducted to pursue the normalization of frequency distribution by making approach the coefficient of skewness to nearly zero tbrough SMEMAX transformation and to get probable minimum flows can be acquired by means of transforrnation equation which has been derivated by SMEMAX method to the annual minimum flow series of five watersheds along Geum river basin. The results obtained through SMEMAX method were compared with probable minimum flows according to return periods by Type III extremal distribution which has been determined as the best fitted one among probablility distributions for the analysis of minimum flow. All the results obtained through this study are summarized as follows. 1.SMEMAX transformation based on median value was proved to be the best method when the coefficient of skewness has less reliability because of the short duration for the observation and were not affected by accidental outliers. 2.SMEMAX transformation has found to be the best one for the coefficient of skewness to be made nearly zero in comparison with log and cubic root transformation. 3.Probable minimum flows according to the return periods were derivated by transformation equations obtained through theoretical analysis of SMEM AX transformation. 4.In general, probable minimum flows by SMEMAX method were appeared as higher values in the range of five and twenty years and as lower ones in the range of below than five and more than fifty years in return periods respectively, in comparison with the results of type III extremal distribution. 5.Relative errors in the probable minimum flows of SMEMAX method to the results of type III extremal distribution were shown to be within ten percent except those of one hundred years in return periods. 6.SMEMAX method was also confirmed to be useful for the analysis of minimum flow frequency as well as flood frequency analysis.

• 한국농공학회지
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• 제34권4호
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• pp.39-47
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• 1992

Derivation of reasonable design low flows was attempted by comparative analysis of design low flows was derived by Power and SMEMAX transformations for the normalizations of skewed distribution and by Type m extremal distribution presented in the first report of this study with annual low flows in the five watersheds of main river basins in Korea. The results were anslyzed and summarized as follows. 1.Basic statistics of annual low flows for the selected watersheds were calculated by using Power and SMEMAX transformations. 2.Power thansformation has found to be the best for the normalization of skewed distribution among others including log, square root and SMEMAX transformations. 3.Design low flows for the selected watersheds were derived by the Power and SMEMAX transformations. 4.Judging by the relative suitabilities of the Type III extremal distribution, Power and SMEMAX transformation, it was found that design low flows of all methods are closer to the observed data within 10 years of the return period and those of Power transformation can be acknowledzed as a reasonable one among others from the viewpoint of the median between values of Type m extremal distribution and SMEMAX transformation in addition to closing the observed than others over 10 years of the return period.

• 한국농공학회지
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• 제28권3호
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• pp.69-78
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• 1986

This studies were established to find out the characteristics of frequency distributiom for the number of occurrence and magnitude, probable flood flows according to the return periods, design floods, and design frequency factors for the studying basins in relation to the risk levels which can be correlated with design return period and the life of structure in the non-annual exceedance series. Eight watersheds along Han, Geum, Nak Dong and Seom Jin river basin were selected as studying basins. The results were analyzed and summarized as follows. 1. Poisson distribution and Exponential distribution were tested as a good fitted distributions for the number of occurrence and magnitude for exceedance event, respectively,at selected watersheds along Han, Geum, Nak Dong and Seom Jin river basin. 2.Formulas for the probable flood flows and probable flood flows according to the return periods were derivated for the exponential distribution at the selected watersheds along Han, Geum, Nak Dong, and Seom Jin river basin. 3.Analysis for the risk of failure was connected return period with design life of structure in the non-annual exceedance series. 4.Empirical formulas for the design frequency factors were derivated from under the condition of the return periods identify with the life of structure in relation to the different risk levels in the non-annual exceedance series. 5.Design freguency factors were appeared to be increased in proportion to the return periods while those are in inverse proportion to the levels of the risk of failure. Numerical values for the design frequency factors for the non-annual exceedance series ware appeared generally higher than those of annual maximum series already published by the first report. 6. Design floods according to the different risk levels could be derivated by using of formulas of the design frequency factors for all studying watersheds in the nor-annual exceedance series.

• 한국농공학회지
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• 제37권E호
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• pp.1-9
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• 1995

It is shown that two step power transformation is more efficient for the normalization of frequency distribution with the coefficient of skewness of zero in comparison with others including SMEMAX and power transformations. It is confirmed that the design low flows calculated using power and two step power transformations used in this study are generally nearer to the observed data as compared with those of SMEMAX transformation at all return periods in the applied watersheds of the Kum, Naktong and Yongsan rivers in Korea.

• 한국산학기술학회논문지
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• 제16권10호
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• pp.6534-6542
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• 2015

본 연구에서는 4개 뮤추얼펀드 유형을 대상으로 한국시장에서의 펀드 성과와 펀드 현금흐름 간의 관계를 분석하였다. 주별 및 월별 자료를 사용한 분석결과는 다음과 같다. 첫 번째, 양자 간의 관계는 펀드의 유형에 따라 다르게 나타나고 있으며, 같은 주식형 펀드인 일반주식형 펀드와 인덱스형 펀드 역시 다른 결과를 보여주고 있다. 두 번째, 양자 간의 관계는 펀드시장의 구조변화 이전/이후 기간에서 다른 양상을 보여 시장의 구조변화가 동 관계에 무시할 수 없는 영향을 미쳤음을 보여주었다. 세 번째, 수익률을 추구하는 현금흐름(return chasing flow)은 채권형 펀드에서 가장 강하게 나타났으며, 일반주식형펀드 및 MMF에서는 구조변화 이후 기간에서만 나타났다. 그러나 인덱스형 펀드에서는 전혀 관측되지 않았다. 네 번째, 펀드현금흐름이 향후의 펀드 성과에 미치는 영향은 오직 MMF에서만, 그리고 구조변화 이후의 기간에서만 관측되었다.

• 전기학회논문지
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• 제61권5호
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• pp.698-704
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• 2012

Electric power used in electrical vehicles flows into the substation through the feedback circuit, track circuit. Due to these power conversion equipments in electrical railroads, return current contains harmonics, and it should not affect other communication lines. In this paper, based on the return currents, we measured harmonics and analyzed an influence in railway equipments due to the harmonics. For analysis, we utilize the measured values of return currents measured in track circuits, and predictive values of those compared to the earth methods between the existing electrified sections. Applying the regulations used for Gyeongbu HSL(High Speed Line), the results of measured harmonics have found to be acceptable.