• 한국농공학회지
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• 제38권3호
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• pp.112-126
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• 1996

This study was conducted to develop an optimal runoff bydrograph model by comparison of the peak discharge and time to peak between observed and simulated flows derived by four different models, that is, linear time-invariant, linear time-variant, nonlinear time-invariant and nonlinear time-variant models under the conditions of heavy rainfalls with regionally uniform rainfall intensity in short durations at nine small watersheds. The results obtained through this study can be summarized as follows. 1. Parameters for four models including linear time-invariant, linear time-variant, nonlinear time-invariant and nonlinear time-variant models were calibrated using a trial and error method with rainfall and runoff data for the applied watersheds. Regression analysis among parameters, rainfall and watershed characteristics were established for both linear time-invariant and nonlinear time-invariant models. 2. Correlation coefficients of the simulated peak discharge of calibrated runoff hydrographs by using four models were shown to be a high significant to the peak of observed runoff graphs. Especially, it can be concluded that the simulated peak discharge of a linear time-variant model is approaching more closely to the observed runoff hydrograph in comparison with those of three models in the applied watersheds. 3. Correlation coefficients of the simulated time to peak of calibrated runoff hydrographs by using a linear time-variant model were shown to be a high significant to the time to peak of observed runoff hydrographs than those of the other models. 4. The peak discharge and time to peak of simulated runoff hydrogaphs by using linear time-variant model are verified to be approached more closely to those of observed runoff hydrographs than those of three models in the applied watersheds. 5. It can be generally concluded that the shape of simulated hydrograph based on a linear time-variant model is getting closer to the observed runoff hydrograph than those of three models in the applied watersheds. 6. Simulated hydrographs using the nonlinear time-variant model which is based on more closely to the theoritical background of the natural runoff process are not closer to the observed runoff hydrographs in comparison with those of three models in the applied watersheds. Consequently, it is to be desired that futher study for the nonlinear time-variant model should be continued with verification using rainfall-runoff data of the other watersheds in addition to the review of analyical techniques.

• 수산해양기술연구
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• 제40권1호
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• pp.29-36
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• 2004

선망의 침강 저항 특성을 해명하기 위한 기초 연구로서, 망지의 재료가 다르고 침자량이 동일한 선망 모형의 침강특성을 해석하였다. 실험에 사용한 선망은, 그물실의 직경 및 발의 길이가 같은 폴리프로피렌系 (밀도 0.91g/cm$cm^3$), 폴리아미드系 (밀도 1.14g/cm$cm^3$) 및 폴리에스터系 (밀도 1.38g/cm$cm^3$)의 매듭 없는 망지를 사용하여, 뜸줄의 길이 420cm, 그물의 폭 86cm가 되도록 제작하였다. 이 그물들의 발줄에 침자를 25g, 45g, 60g 의 3 단계로 바꾸어 9종류의 모형그물을 만들고, 각각 PP-25, PA-25, PES-25, PP-45, PA-45, PES-45, PP-60, PA-60 및 PES-60그물이라고 이름을 붙였다. 회류수조의 수로 위에 투망장치를 설치해서 정지 상태의 수중에 투망하고, 관측부 전면에 설치한 비디오 카메라를 이용하여 촬영 녹화하였다. 그리고, 그물에 표시한 측정점의 좌표를 화상해석장치로 읽고 실험치를 구하였다. 여기서, 선망의 수직방향의 침강운동을 나타낸 이론식을 이용하여 수치해석을 행하였는데, 그 결과는 다음과 같다. 1. 침자량이 60g일 때, 아랫자락의 평균 침강속도는 PES그물 12.2 cm/sec로 가장 빠르고, PA그물 11.4 cm/sec, PP 그물 10.7cm/sec 순으로 늦게 나타났다. 2. 망지의 저항계수 $K_D$는, 계산결과 $K_D=0.09(\frac{\rho}{\rho_w})^4$의 관계식으로 나타낼 수 있었다. 3. 그물다발의 저항계수 $C_R$은, 계산결과 $C_R=0.91(\frac{\rho}{\rho_w})$의 관계식으로 나타낼 수 있었다. 4. 선망 투망후 경과시간에 따른 그물 아랫자락의 도달수심에 대한 실험치와 계산치의 관계는 상관성이 매우 높아, 침자량이 25g일 때 meas.=1.04 cal., 45g일 때 meas.=0.99cal.였으며, 60g일 때 meas.=0.98cal.의 관계를 나타냈다.