• Journal of Korean Society of Water and Wastewater
• /
• v.34 no.5
• /
• pp.335-344
• /
• 2020

Due to global climate change, mega-droughts have occurred frequently. Since long-term droughts make it difficult to secure the water resources, water supply needs to be restricted in a reasonable manner. In the event of limited water supply, the waterworks need to develop a restricted water supply strategy. This study showed that analyzing daily water supply could be used to respond to the first stage of a drought. According to an analysis of Korea's major water authorities, there was about 7~21% of room for daily minimum water supply in case of a drought. Restricting the water supply by lowering pressure is a good strategy for local water authorities with high water leakage rate since leakage is inversely dependent with pressure. For this method, it is necessary to quantify water deficiency and pressure at each node using a simulation. Since DDA-based software is not possible to predict changes in demand at nodes with pressure reduction, WaterGEMS, a PDA software, was used to quantitatively predict water shortages and pressures at each node. Locations where water is deficient need to install booster pumps or to be dispatched with water tank truck and bottled water. Without these support, lowering pressure could not be an option for water works. This paper suggests a method for waterworks to plan a drought by lowering pressure to restrict water supply using daily water supply analysis and PDA based simulation.

• Journal of Power System Engineering
• /
• v.16 no.2
• /
• pp.60-65
• /
• 2012

Pneumatic actuators are clean, lightweight, and can be easily serviced, whereas low energy efficiency has been considered as a critical shortcoming compared with corresponding hydraulic and electrical actuators. This study describes a new design method of pneumatic cylinder driving apparatus by lowering a supply pressure. The simulation study demonstrates that the designed system with the proposed method can operate at the smaller energy consumption state compare to the designed system with the conventional method for the specified working conditions.

• 제어로봇시스템학회:학술대회논문집
• /
• 2005.06a
• /
• pp.1278-1282
• /
• 2005

Air mattress is now used widely to prevent the pressure ulcer by reducing the localized pressure peaks. In this paper an air-cell mattress and its pressure control method based on an approximate anthropometric model are presented. The air-cell mattress has eighteen cylindrical air cells made of porous material allowing air leakage to contribute in reducing the development of pressure ulcer by lowering the pressure peak, temperature and humidity. To determine an optimal air-cell pressure appropriate for each user, we divide the parts of the body into four sections such as head, trunk, hip, and leg. Then, the pressure of each section is independently calculated from the weight of each part based on the individual body height and weight and the approximate anthropometric model. Air supply system for the air-cell mattress is implemented by using four electronic solenoid valves and an air compressor, and it is driven by a real-time micro-controller. The experimental results with seven subjects shows that the proposed air-cell mattress is effective for the prevention of the pressure ulcer.

• Journal of Institute of Control, Robotics and Systems
• /
• v.11 no.7
• /
• pp.578-586
• /
• 2005

Air mattress is now used widely to prevent the pressure ulcer by reducing the localized pressure peaks. The pressure control method based on the anthrophometric model of an air-cell mattress developed in this study is presented. The air-cell mattress has 18 cylindrical air cells made of porous material allowing air leakage. Even though the air leakage can contribute to reducing the development of pressure ulcer by lowering the pressure peak, temperature and humidity, the air pressure changes with time and the desired air-cell pressure has to be determined as an optimal value for each user. To select the desired air-cell pressure, we first divide the parts of the body into four sections such as head, trunk, hip, and leg. Then, the pressure of each section grouped with air-cells is calculated from the weight of each part estimated from the individual height and body weight. Air supply system for the air-cell mattress is implemented by using four electronic solenoid valves and an air compressor, and it is driven by a real-time microcontroller. We experimented with five subjects of the contact pressure on skin. The experimental results show that the proposed air-cell mattress is effective for the prevention of the pressure ulcer.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.26 no.9
• /
• pp.441-446
• /
• 2014

In Jeju province, the Citrus is widely spread crop which is the most popular fruit on the island. When the quality of a Citrus is not in a good condition or when its size exceeds or is lower than the set criteria, it is discarded as a waste. In this study, a drying machine for waste Citrus has been developed with 2.6 GHz microwave energy supply to the Citrus at vacuum environment. The vacuum environment of the drying chamber was maintained to reduce the energy supply to the Citrus by lowering the evaporating temperature of the water. The experiment was conducted with variation of the vacuum pressure, interior temperature of the drying chamber, and operating time of the microwave. As a result, the effect of the temperature was shown to be higher than the other two control methods, and it showed with 0.305 g/W evaporation efficiency.

• Transactions of the Korean hydrogen and new energy society
• /
• v.15 no.2
• /
• pp.159-165
• /
• 2004

Fuel cell makes electricity through chemical reaction. Bipolar-plate distribute hydrogen, oxidation using channel geometry condensation of water vapor inside channels of bipolar-plates lowers efficiency of fuel cell. Usually high pressured gas supply is used to solve the water condensation problem with serpentine type channel geometry. In this study, a new channel geometry shows feasible to minimize lowering efficiency due to water condensation through numerical and experimental analysis.