• Journal of the Korean Society for Heat Treatment
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• v.36 no.6
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• pp.382-388
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• 2023

In this study, hydrogen embrittlement (HE) behavior of a SA-723 steel via controlling gaseous hydrogen pre-charging condition has been analyzed. The gaseous hydrogen charging of the SA-723 steel was performed under a constant pressure of 20 MPa of gaseous H₂ at 150℃ and 300℃ for 2 and 6h, and TDS, SSRT and Charpy tests were conducted to analyze the hydrogen embrittlement (HE) behavior of the SA-723 steel. Furthermore, prior to commencing the test, these specimens were coated with Zn to prevent hydrogen from diffusing out of a specimen during the tests. The TDS results showed that the 300℃-6h and 150℃-6h charged steels contain larger amounts of hydrogen than 300℃-2h and 150℃-2h charged steel. The SSRT and Charpy test results also showed the similar trends that the mechanical properties of the steels deteriorate as the amount of hydrogen charged in the steel increases. Therefore, this study suggests that, for SA-723 steel, the charging time parameter is more effective to charge more amount of hydrogen into SA-723 steel, rather than the charging temperature.

• Journal of the Korean Chemical Society
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• v.15 no.6
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• pp.347-352
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• 1971

The variations of the positive and negative electrode potentials, and of internal pressure were measured during the charge of the sealed type Ni-Cd cell. Both polarization characteristics of a paste type Cd-electrode as a gas diffusion electrode in 30% KOH solution and the effects of active carbon electrode as an oxygen consuming auxiliary electrode of the Ni-Cd cell on the charging characteristics of the cell were studied. Peak voltage at the end of charge of the cell is ascribed to the peak at the negative electrode potential, which is due to the concentration polarization by the lack of $Cd^{++}$ ion and oxygen concentration. And the recovery of the negative electrode potential is resulted from depolarization by the increasing diffusion limiting current density with the increasing oxygen pressure. The active carbon electrode was effective as an oxygen consuming auxiliary electrode. The internal pressure of the cell could be maintained below 200mmHg even at one hour rate charge and overcharge by the use of active carbon electrode as an auxiliary electrode.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.32 no.7
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• pp.227-233
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• 1983

Noticing that action of gaseous phase in insulating oil concerns to the discharging characteristics, I investigated the smalness pressure effects on quantity of the partial discharge and discharging pulse frequency. Tests are carried out between the niddle points in insulating oil at pressure being changed by gradual charge of inert gas Ar. At pressure as low as of 0.1-0.5 torr pulse frequency and maximum partial discharge reach peak while at pressure haigher than 20 torr no pulse is observed. The fact that pulse frequency has peak value at certain presure, which is changed either by charging Ar or by adding oil, implies that the action of gaseous phase depends on pressure. Test results are that partial discharge pulse are governed by pressure of Ar-charged oil, and less partial discharge pulses correspond to smaller bubbles whereas more partial descharge pulses correspond to larger bubbles.

• Journal of Power System Engineering
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• v.10 no.1
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• pp.83-89
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• 2006

Recently, the seriousness of high blood pressure was appeared as the most frequent disease of a the whole sickness in the world. However, the treatment of this disease is uncertain and produces an adverse reaction of a medicine therapy. Also, the patients are burdened with a fee for medical treatment. Therefore, in this paper, we studied effectively and financially to execute the treatment of high blood pressure using the Chinese medicine theorem that is recently arousing the great interest of the people. The main theories in this paper are blood vessel theory and acupuncture, respectively. Especially, the composed circuit systems are classified the blood pressure depressor part and the meridian points discrimination part, respectively. The blood pressure depressor part is composed generally of low-frequency generation circuit, charging-discharging circuit, and micro-computer circuit. Finally, this research have the advantage of discrimination parts such as regular voltage generating circuit, stimulus circuit, amplifying circuit, and alarm circuit.

• Proceedings of the KIEE Conference
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• 1990.07a
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• pp.459-461
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• 1990

Me performed an experiment about preionization electron number density of charge transfer type KrF excimer laser. At the total pressure of 1.8 and 2.2 atm with helium (He) buffer gas, the experimental range of the electron number density is 8-9 ${\times}$ 10 cm The distance between electrode and preionization pin is 15 mJ at charging voltage of 27kV,gas pressure of 2.2 atm,gas mixture of F /Kr/He = 0.3/396.7(%).

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.12
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• pp.723-729
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• 2016

This study compared fin-tube and parallel-flow heat pipes for their sensible heat exchange rate, heat recovery amount, and air-side pressure drop. Tests were done with different refrigerant charging rates of 40-60% vol. and air flow rates of 300-1,400. The sensible heat exchange rate was highest for both types of heat pipes at a working fluid charge of 40% vol. and low flow rate. For the parallel-flow heat pipe, the 60% vol. charge is too high and results in a low sensible heat exchange rate. The reason is that the thicker liquid film of the tube wall deteriorates the heat transfer effect. Hence, the optimal charging rate is 40 to 50% vol. The evaporator heat pipe has a larger air-side pressure drop than the condenser section heat pipe. The reason is considered to be condensation water arising from the evaporator surface. Compared to the fin-tube heat pipe, the parallel-flow heat pipe showed better performance with a working fluid charging rate of 48%, volume of 41%, and an air-side pressure drop about 37%.

• Journal of Advanced Marine Engineering and Technology
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• v.39 no.6
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• pp.626-632
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• 2015

The International Maritime Organization (IMO) has adopted several regulations for the prevention of air pollution from ships. In addition, there is a requirement for shipping liners to reduce greenhouse gas emissions. Accordingly, we need to take measurements to ensure that the steps taken are both efficient and environmentally friendly. It has been determined that the application of the Miller cycle in diesel engines has the effect of both reducing the amount of NOx and improving thermal efficiency. However, this method requires a considerably larger charge air pressure. Therefore, we consider a two-stage turbo-charging system, which not only results in a high charging pressure, but also improves the part load performance with an exhaust-gas bypass system or the application of the Miller cycle. Because of complications associated with the two-stage turbo-charging system, it is complex and difficult to realize a design that optimizes matching between diesel engine and turbo-chargers. Accordingly, it is necessary to perform a quantitative analysis to determine the effects and optimal conditions of these different systems in the early stage of system design. In this paper, we develop a simulation program to model these systems, and we verify that the results of this program are reliable. Further, we discuss methods that can be employed to improve its efficiency.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.28 no.4
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• pp.415-424
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• 2004

Cooling the electronic equipment is one of the major focal points of the design process and the key to successful product launch. The two-phase loop thermosyphone which is a good candidate among many available options was investigated fur cooling of the high power amplifiers. The system is composed of evaporator which contains 6 parallel cold plates, fan cooled condenser, gas-liquid separator, and interconnecting tubes. Experiments were performed for several refrigerant charging values, hs and as a experiment result, the optimum charging value fur this system was proposed. In order to optimize the system design, the operating cycle pressure and inlet/outlet temperatures of evaporator and condenser are measured and analyzed. The effect of the three parameters such as flow rate and temperature of condenser cooling air, and thermal load on the evaporator are investigated. The lower the operating pressure and the cycle temperatures are also better to prevent the leakage of the system. The system invesigated in this paper can be directly used for cooling of a real unmanned wireless communication station.

• KIEE International Transactions on Electrophysics and Applications
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• v.12C no.4
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• pp.229-235
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• 2002

The apparent volume resistivity of powders measured by both the tapping and the compressing methods was compared in this study. Factors such as applied voltage, pressure, corona charging, and so on affecting the apparent volume resistivity of polymer powders were also examined experimentally. Powders of polyacrylonitrile and Nylon 11 were mainly used. The values of the apparent resistivity of polymer powders taken by the tapping method turned out to be larger than those taken by the compressing method, which indicates that the apparent volume resistivity of polymer powders depends strongly on the measurement method. The apparent resistivity of polymer powders increased with an increase in applied voltage while it decreased with an increase in pressure, tapping time, and particle size. The influence of the moisture content of powder and corona charging on the resistivity of polymer powders is also discussed.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.4 no.3
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• pp.183-188
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• 2003

Non-molding and welding line happen by the assembly of gas at the connector terminal. There is not good phenomenon of burr by increasing the over injection pressure, the temperatures of die and resin to prevent from them. Therefore, the connector mold to apply the vacuum molding system is developed in this study. The vacuum pressure is controlled systematically with the optimum conditions in the important ingredients of injection molding that are the temperatures of melting resin and die and cooling condition. The badness in charging is cleared by making a vacuum to non-charging part of the deep bottom part of each cavity. And the vacuum system to reduce the cycle time is applied as the study envelopment of molding work. So, the good product and the productivity improvement can be obtained in this study.