• Water for future
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• v.29 no.5
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• pp.161-172
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• 1996

Studied are the existing equations of Hazen-Williams and Colebrook-White, and the equations of Yoo's (1995) mean zero velocity point and mean friction factor developed for the estimation of commercial pipe friction factor. Simple arrangements of pipe network are devised by changing the diameter, flow discharge and length, and the characteristics of four equations are investigated by comparing the computed results of pressures at each node. Three groups of pipe diameter, small, medium, large, are considered in the comparison, and various problems of existing equations are discussed based on the computed results of pressures and velocities.

• Journal of Korea Water Resources Association
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• v.31 no.3
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• pp.327-335
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• 1998

The distribution network is an essential part of all water supply systems. The cost of this portion of any sizable water supply system may amount to most of the entire cost of the project. This study tried to reduce the cost of the distribution system through optimization in system design. To determine pipe diameter considered in water distribution system design, a iterative procedure linked the flow analysis model and optimization model was used. Linear theory was introduced to analyze flowrate and revised-simplex method based on linear programming is used to optimize pipe diameter. This model was applied to wter distribution system with 22 and 35 pipes, and rapidly determine optimized commercial pipe diameters. Keywords : water distribution system, revised simplex method, optimum pipe diameters.

• Proceedings of the Korea Water Resources Association Conference
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• 2015.05a
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• pp.97-97
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• 2015

최근 몇 년간 발생한 도시홍수 피해의 주요 원인은 배수관망의 통수능 부족 때문이다. 2010년과 2011년에 연이어 발생한 서울시 침수피해의 주된 원인도 통수능 부족이라는 것을 관련된 보고서 등에서 확인할 수 있다. 따라서 현재 진행중이거나 계획중인 주요 침수지구의 '하수관거 종합정비 사업'은 주로 합류식 우수관거의 통수능 확보를 위한 사업으로 진행되고 있다. 하지만 침수지역의 관거 통수능 확보를 위한 관경확대는 관거확대 공사비용, 공사에 따르는 교통정체, 주거지역 시민의 피해, 제한된 공사비 등 여러 측면에서 제한될 수 있다. 배수망의 평면계획은 배수망의 유출반응과 밀접한 관련이 있다. 따라서 이 경우 관경확대 이외의 다른 대안으로 합류식 우수관거의 평면계획을 새로이 검토할 수 있다. 본 연구에서는 여덟 방향 깁스모형을 개발하여 기존의 네 방향 깁스모형과 비교하여 배수관망을 더욱 정확히 표현하도록 하였으며, 개발된 깁스모형을 활용하여 신월지구의 배수망 특성을 분석하였다. 또한 깁스모형을 이용하여 분석한 신월지구의 최적 배수관망 평면계획을 SWMM 모델에 적용하여 기존 배수관망 시스템과 최적 배수관망 시스템의 효율성을 검토하고 도시유역 적용성을 검토하였다. 따라서 본 연구의 결과는 깁스모형의 도시 배수망에의 적용성을 높임과 동시에 배수망의 평면계획을 이용하여 유출량 저감을 도모할 수 있는 새로운 대안을 제시할 수 있을 것으로 기대된다.

• Journal of Korea Water Resources Association
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• v.32 no.1
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• pp.71-81
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• 1999

The objective of this study is to develop a model which can design an optimal pipe network system of least cost while satisfying all the design constraints including hydraulic constraints using a genetic algorithm technique. Hydraulic constraints interfaced with the simulation program(KYPIPE) checked feasible solution region. Genetic algorithm(GA) technique is a relatively new optimization technique. The GA is known as a very powerful search and optimization technique especially when solving nonlinear programming problems. The model developed in this study selects optimal pipe diameters in the form of commercial discrete sizes using the pipe diameters and the pumping powers as decision variables. The model not only determines the optimal diameters and pumping powers of pipe network system but also satisfies the discharge and pressure requirements at demanding nodes. The model has been applied to an imaginary and an existing pipe network systems. One system is adopted from journal papers which has been used as an example network by many other researchers. Comparison of the results shows compatibility of the model developed in this study. The model is also applied to a system in Goyang city in order to check the model applicability to finding of optimal pumping powers. It has been found that the developed model can be successfully applied to optimal design of pipe network systems in a relatively simple manner.

• Journal of Korea Water Resources Association
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• v.49 no.5
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• pp.399-410
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• 2016

In case of the application of Hazen-Williams C for design, operation or maintenance of water supply system, field situations always should be reflected on the factors. In this study, the relationships between C factors and influencing factors are analyzed using statistical techniques with 174 measured C factor data collected in periodic inspection for safety diagnosis in multi-regional water supply systems. To analyze their relationships, cross analysis, one-way ANOVA, correlation analysis were conducted. Analysis results showed that C factors had high correlations with both of elapsed year and pipe diameter and were relatively highly affected by coating material among influencing factors with the categorical type. On the other hand, elapsed year, pipe diameter and water type were meaningful influencing factors according to the results of multiple regression analysis. The Cluster analysis revealed that C factors had a tendency of being fundamentally classified on the basis of the elapsed year of about 20 years and the pipe diameter of 1500mm. Although C factors were generally greatly affected by elapsed year, size of pipe diameter relatively had an large influence on values of them in case of large diameter pipes. Lastly, It can be suggested that C factor estimation formulas using multiple regression analysis and clustering analysis in this study, can be applied as decision standards of C factor in multi-regional water supply systems.

• Journal of the Korean GEO-environmental Society
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• v.24 no.12
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• pp.47-52
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• 2023

In order to efficiently maintain heat pipes operated by district heating operators, the facility history and damage history data built by the operator are used to identify key independent variables that are related to the occurrence of damage. Afterwards, the correlation with the frequency of damage was analyzed, and a basic model for estimating the frequency of damage was derived. Considering the correlation with the estimation model based on the use time currently being used by domestic and foreign district heating operators, a simple regression analysis basic model was presented as the independent variable with the highest correlation between continuous variables such as the use time, pipe diameter, burial depth, and insulation level of monitoring system, and the frequency of damage. The remaining independent variables were reflected as factors that modify and supplement the basic model. As a result of the analysis, as in previous research cases, it was confirmed that the analysis model between use time and frequency of damage had the highest correlation between the two variables and could be used as a basic model. Pipe diameter, burial depth, and insulation level of monitoring system information have also been confirmed to have a correlation with the frequency of damage, so they can be used as factors to supplement the basic model.

• 전기의세계
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• v.16 no.4
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• pp.6-10
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• 1967

The deionization behavior in plasma during arc discharge of mercury arc rectifier depends on ambipolar diffusion. It is shown here in the quantitative analysis that a diameter of arc path which affects the mercury arc rectifier characteristics is related with the density of charged particles in plasma, the particle number of extruguish ion, the deionizing time and the recovering time of grid controlled ability. The conclusion would he useful for designing a diameter of arc path of mercury arc rectifier by quantitative method. And it could be applied to the designing of electrical apparatus using arc discharge phenomena.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.11a
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• pp.502-505
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• 2002

본 논문에서는 냉음극 형광램프의 구조 및 동작원리를 파악하고 램프의 특성을 알아본다. 램프의 특성에 영향을 주는 요소인 관경, 관길이, 가스압, 전극등을 최적화 하여야 하고 CCFL(cold cathode fluorescent lamp) 의 휘도가 관선류, 주파수, 가스압력, 주위온도에 의한 영향에 따른 전기적 및 광학적인 특성을 분석하고자 한다.

• The Magazine of the Society of Air-Conditioning and Refrigerating Engineers of Korea
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• v.28 no.4
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• pp.257-264
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• 1999

96년판 NSPC(National standard plumbing code)의 내용 중 급수 및 배수 관경을 결정하는데 사용하는 기구 급배수부하 단위표가 이전에 발행된 것과 내용이 많이 수정되어 소개코져 한다. 주된 변경 내용은 절수형 위생기구 사용에 따른 급배수 부하 단위 변경, 건물용도별 상세한 내용 분류 및 새로운 위생기구의 추가 등이다.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.20 no.5
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• pp.510-521
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• 2008

In the study, experiments are performed in the interaction region combined with wave and current to investigate the characteristics of local scour around submarine pipelines. Wave generator and current generator are used for the experiments and two current directions were used; co-direction and counter direction to the wave. The local scour depths around the pipeline are obtained according to the various pipe diameters(D), wave periods(T), wave heights(H), and current velocities(V). The experiments show that the maximum equilibrium local scour depth increases with pipe diameter, wave period, wave height, and current velocity. Using the experimental results, the correlations of scour depth and parameters such as Shields parameter($\theta$), Froude number(Fr), period parameter, Keulegan-Carpenter number(KC), Ursell number($U_R$), modified Ursell number($U_{RP}$) and ratio of velocities($U_{c}/(U_{c}+U_{m})$) are analyzed. In the interaction region combined with waves and currents, Froude number and Shields parameter are found the main parameters to cause the local scour around the submarine pipelines and this means that current governs the scour within any limits of the currents.