가중회귀분석(加重回歸分析)에 의한 지역화왜곡계수(地域化歪曲係數)의 추정(推定)

조국광 ( Cho Kuk Kwang ),권순국 ( Kwun Soon Kuk ) 한국농공학회 1990 韓國農工學會誌 : 전원과 자원 Vol.32 No.1

The application of the Log-Pearson Type m distribution recommended by Water Resources Council, U. S. A. for flood frequency analysis requires the estimation of the regionalized skew coefficient. In this study, regionalized skew coefficients are estimated using a weighted regression model which relates at-site skews based on logarithms of observed annual flood peak series to both basin characteristics and precipitation data in the Han river and the Nakdong river basin. The model is developed with weighted least squares method in which the weights are determined by separating residual variance into that due to model error and due to sampling error. As the result of analysis, regionalized skews are estimated as - 0.732 and - 0.575 in the Han river and the Nakdong river basin, respectively.

경사지(傾斜地)에서의 토양유실(土壤流失) -지형인자(地形因子)를 중심으로-

조국광 ( Kuk Kwang Cho ),박성우 ( Sung Woo Park ) 한국농공학회 1981 韓國農工學會誌 : 전원과 자원 Vol.23 No.2

土壤流失은 降雨의 性質, 土壤의 特性, 傾斜度 및 傾斜長, 栽培方法에 따라 달라진다. 따라서 土壤流失을 正確하게 豫測하기 爲해서는 위의 6個 因子에 對한 究明이 必要하다. 지금까지 우리 나라에서는 Wischmeier의 土壤流失量 公式(USLE)을 效率的으로 適用하기 爲하여 6個 因子中 降雨因子, 土壤浸蝕性 因子, 作物因子 및 土壤保全因子에 對해서만 硏究가 있는 實情이다. 따라서 本 硏究에서는 傾斜地에서의 傾斜長가 傾斜度가 土壤流失에 미치는 영향을 究明하여 LS 方程式을 誘導하고자 하였다. 京畿道 驪州郡 梁巨里에 있는 農業振興公社 農地保全 試驗圃에서 10個의 裸地 試驗區에 對한 土壤流失量을 測定하여 分析하였다. 10個의 試驗區中 9個는 傾斜度 10%, 20% 및 30% 各各에 對해 10m, 20m 및 30m의 傾斜長으로 되어 있으며, 나머지 1個의 試驗區는 다른 試驗區와의 比較를 爲한 標準區로서 15%의 傾斜度, 20m의 傾斜長으로 되어 있다. 土壤은 禮山統에 속하며 60%의 砂質, 24%의 微砂質 및 16%의 粘土質로 구성되어 있다. 20回의 土壤流失量 測定記錄中 12.7mm以上의 降雨에 依한 9回分의 流失量 測定資料를 回歸分析한 結果 다음과 같은 LS方程式이 유도되었다. 卽, 그러나 傾斜度와 傾斜長因子(LS)는 다른 여러 因子들과의 相互作用(interaction)을 內包하고 있기 때문에 앞으로의 LS因子에 對한 硏究는 여러種類의 土壤에서 傾斜의 條件을 多樣하게 變化시켜 長期間 實驗을 한다면 韓國의 土壤特性에 一般的으로 適用할 수 있는 LS方程式을 誘導할 수 있으리라 思料된다.

有限要素法을 이용한 海水流動解析 (II)

권순국,고덕구,조국광,김준현,Kwun, Soon-Kuk,Koh, Deuk-Koo,Cho, Kuk-Kwang,Kim, Joon-Hyun 한국농공학회 1992 韓國農工學會誌 : 전원과 자원 Vol.34 No.2

The TIDE, finite element model for the simulation of tidal flow in shallow sea was tested for its applicability at the Saemangeum area. Several pre and post processors were developed to facilitate handling of the complicated and large amount of input and output data for the model developed. Also an operation scheme to run the model and the processors were established. As a result of calibration test using the observed data collected at 9 points within the region, linearlized friction coefficients were adjusted to be ranged 0.0027~0.0072, and water depths below the mean sea level at every nodes were changed to be increased generally by 1 meter. Comparisons of tidal velocities between the observed and the simulated for the 5 stations were made and obtained the result that the average relative error between simulated and observed tidal velocities was 11% for the maximum velocities and 22% for the minimum, and the absolute errors were less than 0.2m/sec. Also it was found that the average R.M.S. error between the velocities of observed and simulated was 0.119 m/sec and the average correlation coefficient was 0.70 showing close agreement. Another comparison test was done to show the result that R.M.S. error between the simulated and the observed tidal elevations at the 4 stations was 0.476m in average and the correlation coefficients were ranged 0.96~0.99. Though the simulated tidal circulation pattern in the region was well agreed with the observed, the simulated tidal velocities and elevations for specific points showed some errors with the observed. It was thought that the errors mainly due to the characteristics of TIDE Model which was developed to solve only with the linearized scheme. Finally it was concluded that, to improve the simulation results by the model, a new attempt to develop a fully nonlinear model as well as further calibration and the more reasonable generation of finite element grid would be needed.

유한요소법(有限要素法)을 이용한 해수유동(海水流動) 해석(解析) (I)

권순국 ( Kwun Soon Kuk ),고덕구 ( Koh Deuk Koo ),조국광 ( Cho Kuk Kwang ),김준현 ( Kim Joon Hyun ) 한국농공학회 1991 韓國農工學會誌 : 전원과 자원 Vol.33 No.4

A numerical simulation of a 2-dimensional tidal flow in a shallow sea was performed using the frequency domain finite element method. In this study, to overcome the inherent problems of a time domain model which requires high eddy viscosity and small time steps to insure numerical stability, the harmonic function incorporated with the linearized function of governing equations was applied. Calculations were carried out using the developed tidal model(TIDE) in a rectangular channel of 10m(depth)×4km(width)×25km(length) under the condition of tidal waves entering the channel closed at one end for both with and without bottom friction damping. The predicted velocities and water levels at different points of the channel were in close agreement with less than 1% error between the numerical and analytical solutions. The results showed that the characteristics of the tidal flow were greatly affected by the magnitude of tidal elevation forcing, and not by on surface friction, wind, or the linear bottom friction when the value was less than 0.01. For the optimum size of grid to obtain a consistent solution, the ratio between the length of the maximum grid and the tidal wave length should be less than 0.0018. It was concluded that the finite element tidal model(TIDE) developed in this study could handle the numerical simulation of tidal flows for more complex geometrical conditions.

유한요소법(有限要素法)을 이용한 해수류동해석(海水流動解析)(II)

권순국 ( Kwun Soon Kuk ),고덕구 ( Koh Deuk Koo ),조국광 ( Cho Kuk Kwang ),김준현 ( Kim Joon Hyun ) 한국농공학회 1992 韓國農工學會誌 : 전원과 자원 Vol.34 No.2

The TIDE, finite element model for the simulation of tidal flow in a shallow sea was tested for its applicability at the Saemangeum area. Several pre and post processors were developed to facilitate handing of the complicated and large amount of input and output data for the model developed. Also an operation scheme to run the model and the processors were established. As a result of calibration test using the observed data collected at 9 points within the region, linearlized friction coefficients were adjusted to be ranged 0.0027~0.0072, and water depths below the mean sea level at every nodes were changed to be increased generally by 1 meter. Comparisons of tidal velocities between the observed and the simulated for the 5 stations were made and obtained the result that the average relative error between simulated and observed tidal velocities was 11% for the maximum velocities and 22% for the minimum, and the absolute errors were less than 0.2m/sec. Also it was found that the average R.M.S. error between the velocities of observed and simulated was 0.119m/sec and the average correlation coefficient was 0.70 showing close agreement. Another comparison test was done to show the result that R.M.S. error between the simula-ted and the observed tidal elevations at the 4 stations was 0.476m in average and the correla-tion coefficients were ranged 0.96~0.99. Though the simulated tidal circulation pattern in the region was well agreed with the observed, the simulated tidal velocities and elevations for specific points showed some errors with the observed. It was thought that the errors mainly due to the characteristics of TIDE Model which was developed to solve only with the linearized scheme. Finally it was concluded that, to improve the simulation results by the model, a new attempt to develop a fully nonlinear model as well as further calibrations and the more reasonable generation of finite element grid would be needed.

寡雨連續日數의 頻度解析

朴成宇,趙國光 서울大學校 農科大學 1983 서울대농학연구지 Vol.8 No.1

旱魃이 發生할 경우 반드시 旱害가 있는 것은 아니다. 그러나 旱害는 旱魃로 因하여 發生하게 된다. 따리서 旱魃은 旱害의 必要條件일 뿐 充分條件은 되지 않는다. 旱魃과 旱害와의 關係式은 다음과 같이 表示될 수 있다. 卽, A=f(加旱害能, 耐旱害能) 위式에서 加旱害能은 地點에서의 寡雨現象인 乾燥連續日數(dry-day sequence)로써 나타낼 수 있고 耐旱害能은 農業的인 側面에서 볼 때 用水施設, 土壤의 保水能, 및 土壤水分含有量, 植生의 種類 및 根群域의 狀況 等의 因子가 考慮될수 있다. 따라서 加旱害能과 耐旱害能의 各種 因子들을 組合하므로써 農業的 旱害의 指標가 될 수 있는 作物生産量의 減少로서 나타나는 A의 값을 推定할 수 있다. 本 硏究에서는 加旱害能의 指標가 될 수 있는 確率乾燥連續日數를 算定하였다. 30年 以上의 日降雨記錄을 保有하고 있는 54個 地點을 選定하여 5-8月의 日降雨 記錄으로부터 每月에 對해 累加雨量이 0.0, 5.0, 10.0, 15.0, 20.0, 30.0mm가 되는 最大連續日數를 調査하고 月別, 累降雨量別로 6個의 確率分布函數를 適用하여 適合한 分布型을 찾아낸 후 3,5,10,15,20,30年의 期待年에 該當되는 確率乾燥連續日數(probable dry-day sequence)를 算定하였다. 또한 81個 地點에 對해 4-8月의 月降雨量을 分析하여 確率月寡雨量을 算定하였다. 그러나 本 硏究結果로서는 各 月間에 亘하여 發生되는 旱魃에는 適用하기가 어려운 點이 있으므로 次後의 硏究에서는 月別로 區分을 하지 않고 全期間內에서 必要한 小期間에 發生할 確率乾燥連續日數를 推定할 수 있는 方法이 模索되어야 할 것이다. 또한 앞으로의 旱魃硏究는 流域을 單位로하여 물收支 system을 充分히 把握하고 用水利用 體制에 따른 水源工의 耐旱能力을 究明할 수 있는 綜合的인 물管理 模型을 開發하여 廣域的 農業旱魃의 豫測 및 그 對策을 樹立하는 方向으로 行해져야 할 것으로 思料된다. Drought is not always responsible to drought damage but the latter is caused by the former. Therefore drought is not sufficient condition but only necessary to its damage. The relationship between drought and its damage can be expressed by the following equation. A=f(droughsivity, droughdibility) In the above equation,droughsivity can be delineated by the dry-day sequence which is caused by point little rainfall and in the agricultural fields droughdibility includes the factors of water use facilities, water potential in the soil,soil moisture contents, kinds of cropping system,condition of root zone and so forth. Therefore A-value, which is expressed in the form of reduction of crop yields and indicate the agricultural drought damage, can be estimated by the combination of droughsivity and droughdibility factors. In this study,the probability of dry-day sequence which can be the drought index was estimated. After 54-stations of daily rainfall records more than 30 years were selected,max,dry-day sequence according to the cumulative rainfall of 0.0, 5.0, 10.0, 15.0, 20.0, 30.0mm in each month was checked up making use of the records from May, to Aug. Six kinds of probability distribution function were applied in order to select good-fitted distribution function,and then probable dry-day sequenccs of 3, 5, 10, 15, 20, 30 year recurrence intervals were estimated. Also,by the analysis of monthly rainfall from April to Aug. at 81-stations probable monthly little rainfall was estimated. However, owing to the difficulty of applying the results of this study to the drought occured continuously from one month to the next,in the future research the method which within the total duration of rainy season probable dry-day sequence of short duration can be estimated should be developed. For the drought study in future, it is considered that synthetic Water Management Model that water budget system of watershed unit and drought resisting capability of reservoirs for agricultural use can be evaluated should be developed for the prediction of wide areal agricul tural drought and setting up preventive measure of it.