• The KSFM Journal of Fluid Machinery
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• v.9 no.3 s.36
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• pp.36-43
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• 2006

Recently, micro hydropower and it's useful utilization are taking a growing interest as a countermeasure of global worming by carbon dioxide and exhaustion of fossil fuel. The purpose of this study is to investigate the possibility of extracting micro hydropower wasted by a valve in water supply system using micro cross-flow hydraulic turbine. In order to fulfill the functions of controlling flow rate and pressure in substitute for the valve, air and water are supplied into an air suction hole which is installed on the side wall of micro cross-flow hydraulic turbine. The results show that in case of supplying a lot of air into the air suction hole, about 50% of flow rate and relatively high value of loss coefficient are controlled by the turbine. Moreover, including high possibility of applying the micro cross-flow turbine to water supply system, extended application of the turbine to the water discharge system of drainage and irrigation canal.

• Proceedings of the SAREK Conference
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• 2009.06a
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• pp.392-397
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• 2009

Gravity pressure vessels find their use in the wet oxidation of sewage sludge, which can be defined as the oxidation of organic and inorganic substances in an aqueous solution or suspension by means of oxygen or air at elevated pressures and temperatures. Numerical analyses were carried out for investigating the flow characteristics and wet air oxidation in the reaction vessel with various conditions such as supply oxidation and the supply positions of oxidation, etc. Wet air oxidation is promoted in the vicinity of bottom in the reactor with increase of oxygen supply. Also, it is the best condition to the oxidation supply position of 150 m and oxidation flow of 0.06 kg/s in the GPV reactor as the remnant of sludge and creation of organic acids.

• Proceedings of the SAREK Conference
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• 2008.11a
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• pp.151-156
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• 2008

Water flow characteristics of an apartment complex consisting of 12 buildings and 635 units in total have been investigated numerically. The complex incorporates two zone booster pump water supply system, and some units have pressure reducing valves in them. Input data to a commercial code Flowmaster7 include survey results on the water usage for the last three years, dimension of the water supply system and its operation condition, etc. Calculated static pressures at the inlet of all units are compared with their design and measured counterparts, and they agree quite well with each other. Then, the pressure distributions and volumetric flow rates at all 635 units are estimated. Flow balancing is also attempted by varying the ratio of angle valve of each unit to improve the non-uniformity of flows.

• Knowledge Management Research
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• v.19 no.4
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• pp.77-98
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• 2018

The purpose of this paper is examine the existing relations structure and IT use for collaboration activities on supply chain and their impacts on the performance of supply chain. This study made a design of the research model that was further constructed by integrating the relationship structure, IT exploration, IT exploitation, supply chain collaboration, absorptive capacity, and knowledge creation, efficiency and efficient. The survey data were collected from 378 companies, where firms are facing increased global competitive pressure and heavily utilize SCM to retain their competitive advantages. The authors validated a measurement model with structural equation modelling and tested eight hypotheses. As a result, the absorptive capacity was closely related to trust, IT exploitation and IT exploration, but supply chain collaboration. Examining the effect of supply chain collaboration with two types of absorptive capacity, the authors found positive effect on potential absorptive capacity, but a non-significant effect on realized absorptive capacity. This finding suggests that the improving performance of supply chain not only is related to the relations structure and IT use on supply chain, but also is closely related to the absorptive capacity.

• Journal of the Korean institute of surface engineering
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• v.9 no.3
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• pp.5-8
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• 1976

In this study, a ruture strength of epoxy resin film coated on the leaking spot in waterpipe line was determined, using water pressure, without interrupting water supply. This results could be used for the sealing of water leakage in large size waterpipe lines. An experimental equation {{{{P=Kt^m~ /R^n~ (m=2, n=3.5) }} was also obtained, where P is the rupture pressure, K is constant, t is the thickness and R is the radius of the resin film. From this results, the safe쇼 thickness of the film for a domestic use was calculated with various radii against the maximum pressure.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.30 no.1
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• pp.88-94
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• 2002

For the pressurized propellant supply system of liquid rocket, feed pressure is determined with respect to the chamber pressure of normal combustion state. However, during ignition period the initial chamber pressure is atmosopheric. This may cause overflow, hard-start and even critical damage for the engine. This paper proposes an improved propellant feed system for the stable combustion of liquid rocket. The proposed system utilizes the cavitating venturi to provide stable mass flow rate. Cavitating venturi offers unique flow control capabilities at normal and abnormal combustion state, because flow rate is soley dependent on the upstream absolute pressure and fluid properties, but independent on th downstream condition. Experimental variables are propellant feed pressure and chamber pressure. The effectiveness of cavitating venturi increased when the ratio of actual feed pressure to the cavitating venturi design pressure is increased. It is also found that Kerosene if more effective to supply stable mass flow rate than LOx.

• Journal of the Korean Institute of Gas
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• v.26 no.3
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• pp.38-44
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• 2022

As the supply of hydrogen charging stations for hydrogen supply accelerates due to the hydrogen economy revitalization policy, the risk of accidents is also increasing. Since most hydrogen explosion accidents lead to major accidents, it is very important to secure safety when using hydrogen energy. In order to utilize hydrogen energy, it is essential to secure the safety of hydrogen storage containers used for production, storage, and transportation of liquid hydrogen. In this paper, in order to evaluate the structural safety of a hydrogen-filled pressure vessel, the behavioral characteristics of gas pressure were analyzed by finite element analysis. SA-372 Grade J / Class 70 was used for the material of the pressure vessel, and a hexahedral mesh was applied in the analysis model considering only the 1/4 shape because the pressure vessel is axisymmetric. A finite element analysis was performed at the maximum pressure using a hydrogen gas pressure vessel, and the von Mises stress, deformation, and strain energy density of the vessel were observed.

• Journal of The Korea Institute of Healthcare Architecture
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• v.29 no.4
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• pp.69-77
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• 2023

Purpose: During the COVID-19 pandemic, there have been many cases of converting regular hospital wards into temporary negative pressure isolation wards. The purpose of this study is to evaluate the minimum airflow differences that satisfies the pressure difference criteria(-2.5 Pa) according to airtightness of switching type wards, in preparation for utilization of aging regular wards as negative pressure isolation wards. Methods: Visual inspection and field measurements were conducted using blower door to evaluate airtightness of 5 hospital wards. CONTAM simulation was used to assess the airflow differences when pressure difference between the corridor and wards met the criteria at various levels of airtightness. Results: The ACH₅₀ of evaluated wards ranged from 19.3 to 50.1 h^-1 with an average of 37.0 h^-1, indicating more than four times leakier than other building types. The minimum airflow differences increased as the airtightness of the wards decreased and the size of the wards increased. Implications: When operating rapidly converted negative pressure isolation wards, understanding airtightness is crucial for determining the minimum airflow differences to maintain the pressure differences. The analysis of this study suggests that improving the airtightness of aging rooms is essential and the minimum airflow differences should be suggested considering both the airtightness and size of rooms.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.50 no.5
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• pp.325-332
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• 2022

The vertical take-off and vertical landing (VTVL) function is essential to carry out exploration missions on the moon or Mars. For this, the engine of the exploration vehicle must have appropriate thrust control accuracy and response time. The hybrid rocket engine (HRE) is known to have a high level of thrust control capability that can satisfy these conditions. This study aims to first verify whether the thrust control performance of the developed HRE is suitable for VTVL. To this end, an oxidizer supply system that does not use a pressurization device was adopted, aiming for a mission time of about 10 seconds. In this study, the thrust control characteristics appearing under various supply pressure decreasing conditions were identified through experiments. Appropriate tank and charging conditions were set from the experimental results. In addition, the results of previous studies and current study's test were compared to confirm whether the developed HRE had adequate control performance for VTVL, and finally, the thrust control performance was verified through altitude control simulation.

• Proceedings of the Korea Water Resources Association Conference
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• 2005.09a
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• pp.250-251
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• 2005