• Title/Summary/Keyword: Discharge coefficients

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Diagnosis of Transform Aging using Discrete Wavelet Analysis and Neural Network (이산 웨이블렛 분석과 신경망을 이용한 변압기 열화의 전단)

  • 박재준;윤만영;오승헌;김진승;김성홍;백관현;송영철;권동진
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2000.07a
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    • pp.645-650
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    • 2000
  • The discrete wavelet transform is utilized as processing of neural network(NN) to identifying aging state of internal partial discharge in transformer. The discrete wavelet transform is used to produce wavelet coefficients which are used for classification. The mean values of the wavelet coefficients are input into an back-propagation neural network. The networks, after training, can decide if the test signals is aging early state or aging last state, or normal state.

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An Experimental Study for Drainage Capacity Increment at Surcharged Square Manholes (과부하 사각형 맨홀의 배수능력 증대에 관한 실험적 연구)

  • Kim, Jung Soo;Song, Ju Il;Yoon, Sei Eui
    • Journal of Korean Society of Water and Wastewater
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    • v.22 no.6
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    • pp.619-625
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    • 2008
  • Urban sewer systems are designed to operate in open-channel flow regime and energy loss at square manholes is usually not significant. However, the energy loss at surcharged manholes is considered as one of the major causes of inundation in urban area. Therefore, it is necessary to analyze the head loss associated with manholes, especially in surcharged flow. Hydraulic experimental apparatus which can change the manhole inner profile(CASE I, II, III, and IV) and the invert types(CASE A, B, C) were installed for this study. The experimental discharge was $16{\ell}/sec$. As the ratio of b/D(manhole width/inflow pipe diameter) increases, head loss coefficient increases due to strong horizontal swirl motion. The head loss coefficients for CASE I, II, III, and IV were 0.46, 0.38, 0.28 and 0.37, respectively. Side covers increase considerably drainage capacity at surcharged square manhole when the ratio of d/D(side cover diameter/inflow pipe diameter) was 1.0. The head loss coefficients for CASE A, B, and C were 0.45, 0.37, and 0.30, respectively. Accordingly, U-invert is the most effective for energy loss reduction at surcharged square manhole. This head loss coefficients could be available to evaluate the urban sewer system with surcharged flow.

A Study on Auto-Classification of Acoustic Emission Signals Using Wavelet Transform and Neural Network (웨이블렛 변환과 신경망을 이용한 음향방출신호의 자동분류에 관한연구)

  • Park, Jae-Jun;Kim, Meyoun-Soo;Oh, Seung-Heon;Kang, Tae-Rim;Kim, Sung-Hong;Beak, Kwan-Hyun;Oh, Il-Duck;Song, Young-Chul;Kwon, Dong-Jin
    • Proceedings of the KIEE Conference
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    • 2000.07c
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    • pp.1880-1884
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    • 2000
  • The discrete wavelet transform is utilized as preprocessing of Neural Network(NN) to identify aging state of internal partial discharge in transformer. The discrete traveler transform is used to produce wavelet coefficients which are used for Classification. The statistical parameters (maximum of wavelet coefficients, average value, dispersion, skewness, kurtosis) using the wavelet coefficients are input into an back-propagation neural network. The neurons whose weights have obtained through Result of Cross-Validation. The Neural Network learning stops either when the error rate achieves an appropriate minimum or when the learning time overcomes a constant value. The networks, after training, can decide if the test signal is Early Aging State or Last Aging State or normal state.

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Flood Analysis in the Tidal Reaches of the Nakdong River (낙동강 하류부의 감조구간에 대한 홍수해석)

  • Lee, Joo-Heon;Lee, Eun-Tae;Lee, Do-Hun;Kim, Nam Won
    • Journal of Korea Water Resources Association
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    • v.31 no.3
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    • pp.235-242
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    • 1998
  • The objective of this study is to develope a predictive model for flood forecasting in the tidal reaches of the Nakdong river and to analyze the tidal effects of major flood forecasting station of the Nakdong river by using the hydraulic flood routing. In the calibration process the optimum roughness coefficients as functions of channel reach and discharge were determined and the calibration results suggest that the unsteady hydraulic flood routing model simulated with the optimum roughness coefficients showed close agreement between the calculated and observed stage.

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Estimation of Discharge Coefficients of Overflow Formula for Submerged Structures (수중구조물 월류공식의 유량계수 산정)

  • Yoon, Sung-Bum;Lee, Sang-Min;Kwon, Kab-Keun;Bae, Jae-Seok
    • Proceedings of the Korea Water Resources Association Conference
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    • 2006.05a
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    • pp.408-412
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    • 2006
  • 단면평균 1차원 수치모형의 수중구조물 표현방식으로 흔히 사용되는 월류공식의 유량계수를 범용 난류유동 수치모형인 FLUENT를 사용하여 완전월류와 불완전월류의 전구간에 걸쳐 구하고 공식화한 결과를 제시한다. 수중구조물은 고무댐과 Ogee형 월류보의 2가지를 대상으로 하였다.

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A Study on discharge gas of Fluorescent Induction Lamp (무전극 램프의 방전가스 연구)

  • Kim, Keun;Jeon, Byung-Hoon
    • Proceedings of the KIEE Conference
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    • 2009.07a
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    • pp.1481_1482
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    • 2009
  • Pure Xe, Kr and Ne atoms and Mixures of Xe-Ne used in fluorescent induction lamps(FILs). However standard regulation of FILs is not made up until now. Therefore, the electron transport coefficients, the electron drift velocity W, the longitudinal diffusion coefficient NDL and the ionization coefficient $\alpha$/N in pure Xe, Kr, Ne gases and Xe-Ne mixtures(1:9, 5:5, 7:3) were calculated over the wide E/N range from 0.01 to 500 Td at 1 Torr by two-term approximation of the Boltzman equation.

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Valve Dynamic Analysis of a High Pressure Reciprocating Compressor (고압 왕복동 압축기의 밸브 거동해석)

  • 이안성;홍용주;정영식;변용수
    • Proceedings of the Korean Society of Marine Engineers Conference
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    • 2002.05a
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    • pp.107-111
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    • 2002
  • A complex valve dynamic analysis has been performed with a high Pressure reciprocating gas compressor. Valve dynamic equations, which take into account the flow continuity and cylinder pressure fluctuation, have been derived. Flow coefficients of valves has been analyzed, using CFD models. Results have shown that both of the suction and discharge values behave favorably without any fluttering motions.

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Determination of Resistance Coefficients Using Field Measurements in Natural Rivers (자연하천 현장자료를 이용한 저항계수의 결정)

  • Lee, Jong-Seok
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.32 no.2B
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    • pp.139-147
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    • 2012
  • This study is derived relationships of the resistance coefficients of Darcy-Weisbach and Manning for flow resistance and the dimensionless velocity using many field measurements for 1,875 rivers consist of sand 179, gravel 992, cobble 651 and boulder 53 channels in natural rivers, respectively. The relationships of power law forms are developed as a function of flow discharge, friction slope, and relative submergence by the regression and the semi-empirical method. The measurements distribution of Manning resistance coefficients by the Box-Whisker Plots show the values which ranges from 0.004~0.151 for sand, 0.008~0.250 for gravel, 0.015~0.327 for cobble, 0.023~0.444 for boulder in natural rivers, respectively. Relationships of these semi-empirical and resistance coefficients will be useful to give information in hydraulic engineering.

An Experimental Study for Drainage Capacity Increment at Surcharged Manholes with a 90° Bend (과부하 90° 접합맨홀의 배수능력 증대에 관한 실험 연구)

  • Kim, Jung Soo;Song, Ju Il;Yoon, Sei Eui
    • Journal of Korean Society of Water and Wastewater
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    • v.23 no.4
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    • pp.447-458
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    • 2009
  • Energy loss at manholes, often exceeding friction loss of pipes under surcharged flow, is considered as one of the major causes of inundation in urban areas. Therefore, it is necessary to analyze head loss at manholes, especially in case of surcharged flow. Hydraulic experiments were conducted with three cases. Case A is to test whether the shapes of the manholes influence head loss coefficients. Case B and C were proposed to further reduce head losses by improving the manhole hydraulic efficiency. In case B, the joining part of the pipe at both shapes of manholes is shifted from central part to side part. The test in case C is to check the average head loss coefficient by installing the side benching in square manhole, based on shifted joining part model. The average head loss coefficient for circular and square manhole on case A was 1.6. This did not show much difference of the head loss coefficients in spite of the discharge variation in this case. However, case B and C show large difference between head loss coefficients due to the strong oscillation of water surface and the horizontal swirl motion. The circular and square manholes in case B reduced the head loss by 30% and 6% than ones in case A, respectively. The average head loss coefficient for circular manhole in case B was 1.1. Case C reduced average loss coefficients of the square manhole in case A from 1.6 to 1.1. Accordingly, the circular manhole in case B and the square manhole in case C showed the effective way to reduce the head loss. These head loss coefficients could be available to apply to the urban sewer system with surcharged flow.

Development of Runoff Hydrograph Model for the Derivation of Optimal Design Flood of Agricultural Hydraulic Structures(II) (농업수리구조물의 적정설계홍수량 유도를 위한 유출수문곡선 모형의 개발(II))

  • 이순혁;박명근;맹승진
    • Magazine of the Korean Society of Agricultural Engineers
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    • v.38 no.3
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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.

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