• The Transactions of the Korean Institute of Electrical Engineers
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• v.41 no.5
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• pp.445-458
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• 1992

As one of the forced cooling method of the underground power transmission system, external water cooled system with trough in tunnel was investigated. This study is performed on thermal analysis for a standard condition to determine the cable transmission current of the underground power transmission system about the cooling facility. A parametric study was performed for the inlet water temperatures, flow rates, the inlet air velocities, flow rates and the cooling spans. This study shows that the cable transmission current varies within the allowable limitation in compliance with the variation of inlet water temperatures and flow rates. It exhibits little variations for the most intervals in compliance with the variation of inlet air temperatures and flows. But, the cable transmission current fast reduces for a specified interval and consequently affects the underground transmission system. As a result, when the actual forced cooling system is designed, the design conditions of inlet air have to be considered as the most important parameters in determination of the cable transmission current.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.4 no.4
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• pp.263-276
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• 1992

The transmission current in a power cable is determined under the condition of separate pipe cooling. To this end, the thermal analysis is conducted with the standard condition of separate pipe cooling system, which constitutes one of the underground power transmission system. The changes of transmission current in a power cable with respect to the variation of temperatures and flow rates of inlet cooling water as well as the cooling spans are also determined. As a consequnce, the corresponding transmission current is shown to vary within allowable limit, resulting in the linear variation of the current for most of the cable routes. The abrupt changes of current, however, for the given flow rate of inlet cooling water in some cooling span lead to the adverse effects on the smooth current transmission within the underground power transmission system. In practice, it is expected that the desinging of the separate pipe cooling system in conjunction with the evaluation of system capacity should take into account the effects of design condition on the inlet cooling flow rate.

• Journal of Korean Society of Water and Wastewater
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• v.30 no.5
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• pp.491-500
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• 2016

Pressure monitoring is expected to be expanded in a water distribution system according to accelerated development of smart water network management technologies caused by appearances of affordable digital infrastructures like computing, storage and bandwidth. However, the placement of pressure sensors has been determined by engineer's technical decisions since there is no well-defined criteria for deciding a suitable location of pressure sensor. This study presents a placement method of pressure sensors based on the consideration of allowable error in calibrating water network analysis modeling. The proposed method is to find a minimum set of pressure sensors for achieving a reliable management of water transmissions main and increasing the efficiency of their real-time operation. In the case study in Y area's transmission main, the proposed method shows equally distributed pressure sensors in terms of hydraulics. It is expected that the proposed method can be used to manage transmission mains stably and construct a robust real-time network analysis system as a minimal criteria.

• Journal of the Society of Naval Architects of Korea
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• v.50 no.3
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• pp.153-159
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• 2013

The power transmission system has always been considered critical for a human powered boat(or water bike) since it first showed up at Human Powered Vessel Festival. Mechanical problems, such as abrasions and other damages of the gear system for the power transmission, lead to poor durability and low efficiency of a boat. This paper described mechanical problems and a design process of power transmission system and then suggested the method to solve the problems. It is selected a module and a type of gears that are structurally stable thus can transmit the power durable. Especially the lower gear box is applied to CRP(contra rotating propeller) system for improving the structural stability and the propeller efficiency as well. As the results, the upper and lower gear box are designed and manufactured. And from the trial test, it is confirmed that the power transmission system is reliable.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.28 no.11
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• pp.1322-1331
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• 2004

This paper presents studies on the design of water hydraulic system and components to replace oil with tap-water as the pressure transmission medium in hydraulic systems. In order to improve the performance of water hydraulic system, the thermal and hydraulic properties of tap-water are first investigated. Based on these characteristics, the design parameters, such as the clearances of the moving parts, the cross-sectional area of pipes and relative roughness, are proposed so that the performance of water hydraulic system is the same as that of oil. In addition, the operating ranges, which show the possibility of using water hydraulic system, are examined.

• Journal of Korea Water Resources Association
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• v.51 no.12
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• pp.1171-1180
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• 2018

Korea's water transmission system is operated by the nonpressure flow method that flows from highlands to lowlands due to the nature of Korea with many mountainous areas. In order to store water in the highlands, the water pumps are installed and operated. However, In this process, a lot of electrical energy is consumed. therefore, it is necessary to minimize the energy consumption by optimizing the size and operation schedule of the water pumps. The optimal capacity and operation method of the water pump are affected by the size of the tank (distributing reservoir). Therefore, in order to economically design and operate the water transmission system, it is reasonable to consider both the construction cost of the water pump and the tank and the long-term operation cost of the water pump at the step of determining the scale of the initial facilities. In this study, the optimum design model was developed that can optimize both the optimal size of the water pump and the tank and the operation scheduling of the water pump by using the genetic algorithm (GA). The developed model was verified by applying it to the water transmission systems operated in Korea. It is expected that this study will help to estimate the optimal size of the water pump and the tank in the initial design of the water transmission system.

• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 2005.10a
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• pp.85-90
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• 2005

A Water Level gauge which composes a water supply system for water demand, information transmission system and the solar storehouse electromotive floodgate, regarding the structure plan and a production of the nothing power automatic floodgate it described. The important point must solve but urgently will compare the water amount used from system establishment place or not one. and It must give proof the efficient characteristic of system, must solve the technical problem portion against revision of the accuracy of upper downstream canal which is information transmission system of the Self-controlled check gate. The solar floodgate is more economic with the base which will reach and the system construction which is accurate.

• Journal of Institute of Control, Robotics and Systems
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• v.13 no.2
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• pp.128-132
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• 2007

Thermal Imaging systems are reported to be crucial for fire fighting and beginning to be used by fire fighters. The performance of thermal imaging system is determined by both the radiation of infrared from the target and the attenuation of infrared signal in the optical path by the absorption, scattering, diffraction and reflection. In the scene of fire, water drops with various sizes such as vaporized water, wafer mist from sprinkler, and wafer to suppress the fire reside with various gas generated by burning. To measure the transmission of infrared radiation in the scene of fire, fire simulating system and thermal imagers with cooled detector which detects $3{\sim}5{\mu}m$ infrared and uncooled detector fabricated by the MEMS technology which detects $8{\sim}12{\mu}m$ infrared. are made. With thermal imagers and Ire simulating system, the change of thermal image with respect to the change of visibility controlled with the burned fas was measured. It was found that the transmission of infrared was not reduced by the burned gas, which could be explained by the long wavelength of infrared ray compared with visible ray. However, the transmission of infrared ray was largely reduced by the combination of burned gas and water mist supplied by sprinkler. This is contrary to the results of calculated transmission through the pure water mist and shows that the transmission of infrared ray is mostly affected by the compounds of water mist and burned gas. In this case, it was found that the uncooled detector which detects $8{\sim}12{\mu}m$ infrared ray is better than cooled detector which detects $3{\sim}5{\mu}m$ infrared ray for fire fighting.

• Journal of Korean Society of Water and Wastewater
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• v.27 no.1
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• pp.129-138
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• 2013

Water interruption is often caused by a rupture in the branch-like singular pipeline. This will cause critical complaints from household and may decrease public service quality. As an alternative of singular pipeline, additional parallel pipeline could be installed for sustainable water supply. This system is called double pipeline system and able to be utilized for water transmission line between treatment plant and distribution reservoir. Construction of double pipeline was thought to increase capital cost, which can be an issue to waterworks authorities. Reducing capital cost was possible by means of installing connectors between two parallel pipelines because of reduced diameter of each pipe. To obtain optimal design condition for connectors, it was necessary to compare water pressure according to accident location, to investigate flow according to connection pipe spacing, connection pipe diameter, and aging of pipe. Reliable and economical connection layouts were determined based on these results. The cost estimation for each design condition was carried out. Cost was approximately reduced by 20 ~ 30 % compared to the double pipeline without connections. In addition to this, connection between double pipelines could expect extra benefits for maintenance since the pipe could be repaired and rehabilitated without interruption.

• Journal of Bio-Environment Control
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• v.25 no.4
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• pp.270-276
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• 2016

This study analysed overall heat transfer coefficient, heat transmission, and rate of indoor air heating provided by water curtain in order to determine the heat transfer characteristic of double-layered greenhouse equipped with a water curtain system. The air temperatures between the inner and outer layers were determined by the water flow rate and inlet water temperature. Higher water flow rate and inlet water temperature resulted in the increased overall heat transfer coefficient between indoor greenhouse air and water curtain. However, it was found that with higher levels of water flow rate and inlet water temperature, indoor overall heat transfer coefficient was converged about $10W{\cdot}m^{-2}{\cdot}^oC^{-1}$. The low correlation of overall heat transfer coefficient between water curtain and air within double layers was likely because the combination of greenhouse shape, wind speed and outdoor air temperature as well as water curtain affected the heat transfer characteristics. As water flow rate and inlet water temperature increased, the heat transferred into the greenhouse by water curtain also tend to rise. However it was demonstrated that the rate of heat transmission from water curtain into greenhouse with water curtain system using underground water was accounted for 22% to 28% for total heat lost by water curtain. The results of this study which quantify heat transfer coefficient and net heat transfer from water curtain may be a good reference for economical design of water curtain system.