• 제목/요약/키워드: Discharge coefficients

검색결과 260건 처리시간 0.022초

고주파 점등 형광램프의 비선형 저항 모델에 관한 연구 (A Study on the Nonlinear Resistance Model of a F/L Operating in High Frequency)

  • 지철근;장우진
    • 한국조명전기설비학회지:조명전기설비
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    • 제1권2호
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    • pp.49-56
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    • 1987
  • 에너지 절약을 위하여 방전등을 고조파 전원으로 동작시킨다. 방전등을 포함한 고조파 전원 회로를 설계할 경우, 램프의 특성을 알아야하며, 이에 많은 방법과 수식 모델이 제안되고 있다. 본 연구에서는, 에너지 절약 효과가 큰, 형광램프의 전압-전류 특성을 나타내기 위하여, 비선형 저항 모델을 제안하고, 이를 인덕터 및 커패시터 안정기를 사용한 회로에 적용, 그 유용성을 검증하였다. 이 수식 모델은 다른 모델과는 달리 비교적 쉽게 얻을 수 있다. 또한, 비교를 위하여, 수정된Francis 방정식을 이용한 방법을 검사하였다. 본 연구에 사용된 방법은 기본적으로 다른 방전등에도 적용이 될 수 있다. 결과로서, 1) 3차 다항식의 비선형 저항 모델로 좋은 결과를 얻을 수 있다. 2) 고조파 점등시, 상수 계수를 사용하는 수정된 Francis 방정식은 적용할 수 없다.

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심부지열 용 동축 열교환기 성능예측을 위한 열전달 실험 및 해석 (Heat Transfer Experiment and Analysis to Predict the Efficiency of Heat Exchanger for Deep Geothermal System)

  • 정국진;정윤성;박준수;이동현
    • 융복합기술연구소 논문집
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    • 제7권1호
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    • pp.1-6
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    • 2017
  • The Heat exchanger for deep geothermal system is very important to enhance the efficiency of the system. The co-axial heat exchanger is used due to the limitation of digging space. The heat transfer on the external surface of outer pipe should be high to receive a large amount of heat from the ground. However, the inner pipe should be insulated to reduce the heat loss and increase the temperature of discharge water. This study made experiment apparatus to describe the co-axial heat exchanger and measure the heat transfer coefficients on the internal and external surface. And the pin-fin was designed and fixed on the internal surface to increase the efficiency of heat exchanger. Finally, we calculated the temperature of discharge water using the heat transfer circuit of co-axial heat exchanger and heat transfer coefficient which from experimental results. The water temperature was reached the ground temperature at -500 m and following the ground temperature. When the water return to the ground surface, the water temperature was decreased due to heat loss. As the pin-fin case, the heat transfer coefficient on the internal surface was decreased by 30% and it mean that the pin-fin help to insulate the inner pipe. However, the discharge water temperature did not change although pin-fin fixed on the inner pipe.

관절경 수술환자의 불확실성에 미치는 영향요인 (Factors influencing of uncertainty on patients with arthroscopic surgery)

  • 정지영;김민숙;조유나
    • 한국융합학회논문지
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    • 제9권6호
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    • pp.311-319
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    • 2018
  • 본 연구는 관절경 수술환자의 불확실성, 불확실성평가, 자기효능감의 정도를 파악하고 불확실성에 미치는 영향요인을 파악하고자 시도되었다. 자료 수집은 관절경 수술 후 퇴원을 앞둔 대상자 중 연구에 동의하고 설문지를 완성한 131명을 대상으로 하였다. 자료 분석은 SPSS 18.0을 이용하여 t-test, ANOVA 및 Scheffe 사후검정, Pearson correlation coefficients 산출 및 다중회귀분석을 실시하였다. 연구결과는 교육수준, 배우자유무, 수술 전 한방치료경험, 자기 효능감이 불확실성에 의미 있는 영향을 미치는 것으로 나타났다. 본 연구결과를 통해 관절경 수술환자의 불확실성을 감소시키기 위해 입원 중, 퇴원 전 교육 프로그램 개발을 제언한다.

Non-Darcy 흐름특성을 고려한 최종체절 수리특성분석 (Hydraulic Characteristic Analysis of Final Closing considering Non-Darcy Flow)

  • 최흥식
    • 한국수자원학회논문집
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    • 제37권8호
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    • pp.613-622
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    • 2004
  • Non-Darcy 제체내 침투수 흐름과 배수갑문을 통한 흐름의 특성을 고려한 최종체절의 수리특성분석 모형에 의한 해석결과는 실측자료와 잘 일치하여 개발된 모형의 적용성이 있음을 보여주었다. 실측치와의 비교에서 본간(1985) 식에 의한 계산결과가 나정우(1987)에 의한 방법보다 비교적 정확함을 보여주었다. 아울러 완전 또는 불완전 월류의 구분이 없이 완전월류식에 잠수도를 이용한 유량계수식을 사용한 나정우 식의 사용성을 보여 주었다. 본간 식과 나정우 식에 의한 계산 값이 실측치보다는 유출입 특성이 크게 나타나 현장에서 체절구간의 불규칙적인 단면 양상을 감안한 유량계수의 조정이 필요할 것으로 판단된다. 일반적으로 최종체절의 수리특성 분석에서 제체구간의 침투수 흐름의 고려는 Darcy 흐름에 기초하여 분석하여왔다. 제체내 침투수의 유량과 개방구간을 통과하는 유량의 비가 체절구간이 좁을수록 크게 나타나, 제체내 침투수의 정확한 해석에 의한 체절구간의 수리특성을 분석해야할 필요가 있다.

수치해석모형에 의한 홍수추적 (Flood Routing Using Numerical Analysis Model)

  • 이용직;권순국
    • 한국농공학회지
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    • 제31권1호
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    • pp.117-130
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    • 1989
  • In this study, an implicit one-dimensional model, DWRM(Dynamic Wave Routing Model) was developed by using the four-point weighted difference method. By applying the developed model to the Keum River, the parameters were calibrated and the model applicability was tested through the comparison between observed and computed water levels. In addition, the effects of the construction of an estuary dam to the flood wave were estimated as a result of the model application. The results of the study can be summarized as follows; 1. The roughness coefficients were evaluated by comparison between observed and computed water level at Jindu, Gyuam and Ganggyeung station in 1985. The Root Mean Squares for water level differences between observed and computed values were 0.10, 0.11, 0. 29m and the differences of peak flood levels were 0.07, 0.02, 0. 07m at each station. Since the evaluated roughness coefficients were within the range of 0.029-0.041 showing the realistic value for the general condition of rivers, it can be concluded that the calibration has been completed. 2. By the application of model using the calibrated roughness coefficients, the R. M. S. for water level differences were 0.16, 0.24, 0. 24m and the differences of peak flood level were 0.17, 0.13,0.08 m at each station. The arrival time of peak flood at each station and the stage-discharge relationship at Gongju station agreed well with the observed values. Therefore, it was concluded that the model could be applied to the Keum River. 3. The model was applied under conditions before and after the construction of the estuary dam. The 50-year frequency flood which had 7, 800m$^3$/sec of peak flood was used as the upstream condition, and the spring tide and the neap tide were used as the downstream condition. As the results of the application, no change of the peak flood level was showed in the upper reaches of 19.2km upstream from the estuary dam. For areas near 9.6km upstream from the estuary dam, the change of the peak flood level under the condition before and after the construction was 0. 2m. However considering the assumptions for the boundary conditions of downstream, the change of peak flood level would be decreased.

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낙동강 유역에서의 확정론적 및 추계학적 수질해석 (Deterministic and Stochastic Water Quality Analysis in the Nakdong River)

  • 한건연;최현상;김상호
    • 한국수자원학회논문집
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    • 제35권4호
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    • pp.385-395
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    • 2002
  • 하천에서의 수질변동을 예측하기 위해 FOEA(First-Order Error-Analysis)와 Monte Carlo 모의를 적용한 추계학적 모형을 개발하였다. 영향메트릭스(Influential matrix)를 이용한 민감도 분석을 실시하여 주요 반응계수를 결정하였고, BFGS(Broyden-Fletcher-Goldfarb-Shanno) 최적화 기법을 사용하여 주요 반응계수 값을 산정하였다. 본 모형을 확정론적 수질해석과 동일한 실제 하도구간에 적용하여 추계학적 수질해석을 실시하였고, 그 결과는 확정론적 해석결과와 잘 일치하였다. 유량과 수질, 반응계수 등에 포함된 불확실도가 하류단의 불확실도에 끼치는 영향을 산정하기 위해 상류단과 지류의 유량 및 수질에 대한 불확실도, 그리고 반응계수의 불확실도에 대한 분석과정이 모형에 포함되었다. 모의수행 결과로부터 각 변수들이 가지고 있는 불확실도가 총 불확실도에 끼치는 영향에 대한 기여도를 산정 할 수 있었다.

산림소유역에서 MUSLE 유출에너지인자 계수값의 적용성 평가 (Evaluation on MUSLE Runoff Energy Coefficient in Small Forest Watershed)

  • 김재훈;최형태;임홍근
    • 한국환경복원기술학회지
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    • 제18권6호
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    • pp.191-200
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    • 2015
  • This study was carried out to investigate coefficient and exponent of runoff energy in MUSLE for small forest watershed, Hwachoen watershed in Gangwon-do. For 15 rainfall events, runoff volume, peak discharge and sediment yield were measured and these data were used to calculate coefficient and exponent of runoff energy. The results of this study showed that $LS{\bullet}K{\bullet}C{\bullet}P$ factors of MUSLE were affected by slope steepness. The coefficient and exponent of runoff energy were validated with coefficient of efficiency of 0.92 and these values were suggested to 0.002 and 0.81 respectively. The comparison of the coefficients and exponents between Hwacheon and other forest watersheds showed that these values would reflect the effect of forest management within watershed.

소형터보압축기 회전차와 볼류트의 상호작용 (Interaction of Impeller and Volute in a Small-size Turbo-Compressor)

  • 김동원;안병재;김윤제
    • 대한기계학회:학술대회논문집
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    • 대한기계학회 2001년도 춘계학술대회논문집E
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    • pp.807-812
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    • 2001
  • The effects of casing shapes on the interaction of the impeller and volute in a small-size turbo-compressor are investigated. Numerical analysis is conducted for the compressor with circular and single volute casings from inlet to discharge nozzle. In order to predict the flow pattern inside the entire impeller, vaneless diffuser, and casing, calculations with a multiple frame of reference method between the rotating and stationery parts of the domain are carried out. For incompressible turbulent flow fields, the continuity and three-dimensional time-averaged Navier-Stokes equations are employed. To predict the performance of two types of casings, the static pressure and loss coefficients are obtained with various flow rates. Also, static pressure distributions around casings are studied for different casing shapes, which are very important to predict the distribution of radial load.

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컴플라이언스 계수에 의한 노즐하중 하에서의 원심펌프의 축단변위에 관한 연구 (A Study on the Shaft End Displacement of the Centrifugal Pump under Nozzle Loads using Compliance Coefficients)

  • 최복록;박진무;김광은
    • 한국정밀공학회지
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    • 제17권4호
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    • pp.233-239
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    • 2000
  • Investigation results are presented fur the shaft end displacements due to the elastic deformation of the casing and support in double suction centrifugal pump. Suction and discharge nozzles of the pump are subject to external piping loads and, in API 610, maximum values of their components are specified. This means that each nozzle can be subject to various combinations of loading conditions. Considering upper and lower criteria of each load, we must perform for the 4,096 load cases, and assign the direction and range of the loads. So, this paper develops an efficient procedure(Compliance Coefficient Method) to calculate the shaft end displacements(@ coupling) to determine whether satisfying the pump's standard. Also, we analyzed the effects of the casing and support thickness on shaft end displacements.

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창원지역 지하수 수질과 DRASTIC에 의한 지하수 오염취약성 평가

  • 김무진;함세영;정재열;장성;차용훈
    • 한국지하수토양환경학회:학술대회논문집
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    • 한국지하수토양환경학회 2004년도 총회 및 춘계학술발표회
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    • pp.459-462
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    • 2004
  • This study assesses groundwater vulnerability to contaminants in 12 administrative districts of the city of Changwon, using DRASTIC technique. DRASTIC was originally applied to situations in which the contamination sources are at the ground surface, and the contaminants flow into the groundwater with infiltration of rainfall. However, groundwater contamination in urban areas can also be related to excessive pumping resulting in a lowering of the water level. The correlation coefficient between minimum DRASTIC indices and the degree of poor water quality for 10 districts is low as 0.40. The correlation coefficients between minimum DRASTIC indices and the groundwater discharge rate, and between minimum DRASTIC indices and well density per unit area are 0.70 and 0.87, respectively. Thus, to evaluate the potential of groundwater contamination in urban areas, it is necessary to consider other factors such as groundwater withdrawal rate and well density per unit area with ratings and weights as well as the existing six DRASTIC factors.

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