• The KSFM Journal of Fluid Machinery
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• v.3 no.1 s.6
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• pp.28-36
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• 2000

For the improvement of the pump characteristics in the partial capacity range, it must be verified that the influence of the impeller design factor on the internal flows and the influence of the impeller internal flows on the pump characteristics. In this paper, in order to understand the influence of outlet angles on flow conditions and characteristics of a mixed flow pump, experiments were carried out for four kinds of impeller, which have the same inlet angle distributions and meridional section shapes. Results shown that separation and stall in the partial capacity range were enlarged by the outlet angles. The relationship between the separation and the stall at the impeller and the discharge flow conditions were clarified.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.21 no.8
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• pp.1034-1045
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• 1997

For the improvement of the pump characteristics in the partial capacity range, it must be verified that the influence of the impeller design factor on the internal flows and the influence of the impeller internal flows on the pump characteristics. In this paper, in order to understand the influence of inlet angles on flow conditions and characteristics of a mixed flow pump, experiments were carried out for three kinds of impeller, which have the same outlet angle distributions and meridional section shapes. Results show that separation and stall in the partial capacity range can be controlled by the inlet angles. The relationship between the separation - stall at the impeller leading edge and the discharge flow conditions is clarified.

• Journal of Advanced Marine Engineering and Technology
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• v.38 no.10
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• pp.1347-1353
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• 2014

It's possible for a human to breathe under water, if dissolved oxygen is effectively used. Fish can stay under water using the gill which extracts dissolved oxygen from water. Water includes small amounts of oxygen, so a human needs larger amounts of water to acquire oxygen enough for underwater breathing. The exhalation gas from a human is another method to get higher amounts of oxygen under water. It mainly composes of oxygen, nitrogen and carbon dioxide. So, if only carbon dioxide is decreased, the exhalation gas has good characteristics for breathing of a human under water. In this paper, composition of the exhalation gas from a human was analyzed using GC. Based on these results, the synthesized gas was prepared and mixed into water which was used for experimental devices to analyze separation characteristics of dissolved gases from water. Experimental devices included a water pump, a hollow fiber membrane module and a vacuum pump. The effects of pressure and water flow on separation characteristics of synthesized gas were investigated. The compositions of gases separated from water using synthesized gas were investigated using GC. These results expect to be applied to the development of underwater breathing technology for a human.

• Journal of Advanced Marine Engineering and Technology
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• v.40 no.10
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• pp.916-921
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• 2016

It is possible for humans to breathe underwater using dissolved oxygen. However, unlike fish, humans need large amounts of oxygen to breathe underwater. Water generally contains small amounts of dissolved oxygen. To get enough dissolved oxygen from water, great volumes of it should be supplied into a separation device. If exhalation gases are used, the amounts of water supplied into the membrane can be decreased. However, the characteristics of exhalation gases after passage through the separation device need to be investigated. To reuse the exhalation gases, the concentration of carbon dioxide should be decreased. A compressor is needed to supply the exhalation gases because of the high pressure generated in the membrane inlet. However, compressors require a lot of power and are heavy, so it is not proper to get the portable separation device. A system without the compressor is needed. If the pressure of the position mixed from the exhalation is less than atmosphere, the compressor is not needed. In this thesis, characteristics of the gases which are mixed with exhalation gases and separated from water after passing the membrane are investigated. The compositions of carbon dioxide, oxygen, and nitrogen are measured with the gas chromatography. The effects of water and exhalation gas flow rates on characteristics of gases separated from water after the membrane are showed.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.49 no.5
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• pp.352-357
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• 2000

This paper presents about an example of circuit design and characteristics of inverter according to the variable capacitance of the DC voltage source separation capacitor used in ZVS-HB type high frequency resonant inverter. The soft switching technology known as ZVS is used to reduce turn off loss at switching. In the event the capacitance of the DC voltage source separation capacitor is varied, the analysis of inverter circuit has generally described by using normalized parameter and operating characteristics have been evaluated in terms of switching frequency and parameters. According to the calculated characteristics value, a method of the circuit designs and operating characteristic of the inverter is also presented in this paper. In addition, this paper proves the validity of theoretical analysis through the experiment. This proposed inverter shows that it can be practically used in future as power source system for the lighting equipment of discharge lamp, DC-DC converter etc.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.30 no.2 s.245
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• pp.177-185
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• 2006

This study aims deriving analysis the flow characteristic of kitchen hood system with using 3-D numerical analysis method and improving the system to expel pollutes more efficiently. To understand the flow characteristics of four models, this study only focuses on velocity field, temperature field, and concentration field varying with followings whether separation plate is set or not and the shapes of separation plates. The quantity of air, speed of exhaust fan and temperature and concentration of heating source are concerned as constant values. The three models having different shapes have one exhaust port and the model which has the vent at the closest position to where pollutes are generated is discovered to be the most efficient model. Compare to the initial model (having no separation plate), it was $1.4-1.9\%$ more efficient at temperature distribution and $9.4-11.9\%$ more at $CO_2$ concentration distribution.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.266-267
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• 2017

A numerical investigation of the stage separation behavior of two-body vehicle focusing on its flow characteristics were carried out. For this simulation, separation of a booster from vehicle was modeled by a chimera grid system and calculated by using commercial code, CFD-FASTRAN$^{TM}$. Consideration of a spring force, gravity and relative acceleration of a booster was the essential factor that simulates the realistic situation. In this study, It was validated that the booster separation time decreases with increase in flight mach number and angle of attack. In view of the results so far achieved, it was expected that the dynamics modeling and boundary condition set up applied in this study will be helpful in a estimation of a safe stage separation and event sequence of flight test.

• Membrane Journal
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• v.13 no.3
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• pp.154-161
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• 2003

We measured the permeation characteristics of water with the hydrophobic PTFE membranes dependent on water temperature to confirm the separation of oxygen isotopes using Air Gap Membrane Distillation (AGMD) and Vacuum Enhanced Membrane Distillation (VEMD). Isotopic concentrations of $H_2^{16}O$ and $H_2^{18}O$ of the permeated water vapor were measured by Diode Laser Absorption Spectroscopy. Concentrations of the heavy oxygen isotopes in the permeated water vapor were decreased. Isotope separation coefficients for the hydrophobic PTFE membranes were 1.004∼1.01 depending on the experimental conditions. We observed the effects of air in membrane pores on the oxygen isotope separation. Isotope separation coefficients for the hydrophobic PTFE membranes without air in pores are higher than those for the membrane with air in pores.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.45 no.7
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• pp.539-549
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• 2017

In this paper, experimental studies on the shroud separation were performed to investigate characteristics of the shroud separation at mach 3. Shroud separation tests were carried out in the vertical free-jet wind tunnel that is capable of testing separable structures. A shroud model was miniaturized to meet test objectives and test section dimensions of the wind tunnel. Pneumatic Locking and separation mechanisms were designed considering external force due to free stream. High speed cameras were used to record the shroud motion and unsteady shock patterns over the deploying shrouds during the shroud separation process. Also, unsteady pressures on the nose surface were measured by using the pressure sensors. Through the tests, the measurement data necessary for researches on the shroud separation technology were obtained. Shroud separation behaviors and characteristics of unsteady pressure on the nose surface for each external flow conditions were analyzed.

• Aerospace Engineering and Technology
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• v.4 no.2
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• pp.199-202
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• 2005

Separation motion of 1:2 downscaled nose fairing is simulated. In comparison with the experimental results, results of analyses on the separation simulation are verified and the characteristics of nose fairing separation are analyzed. The results shows about 5% analysis error.