• Proceedings of the KSR Conference
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• 2011.05a
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• pp.1647-1653
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• 2011

In the case of an urban rail chopper type subway train, varistors have been installed for protecting usual electronic equipments, semiconductor devices(diodes, transistors, thyrister, etc.) communications, measuring, control device and absorbing opening & closing surge of electromagnetic valve. These varistors were steadily reduced dielectric strength as becoming superannuated. Thus there is a problem that reacts more sensitive at the same surge in the general control operation. On existing maintenance, there is not specific standard to replace superannuated varistor. So when maintaining chopper type subway train, all varistors or old varistors that workers checked a discoloration & crack with the naked eye and noticed degradation smell by deterioration are replaced. This study suggests detail standards for judgement that varistors are good or bad chopper type subway train, and it draw a efficient maintenance which efficient maintenance can check more easy the degradation properties variation.

• Journal of the Korean Society of Safety
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• v.25 no.5
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• pp.7-14
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• 2010

Ultra high pressure system, which can be generally increased over 1,000bar, needs to have sealing mechanism to protect leakage and selection of the materials used in the intensifier. Components such as pressure vessel, hydraulic hose assembly, accumulator, hydraulic cylinder, hydraulic valve, pipe, etc., are tested under the impulse-pressure conditions. Components need to be tested under 1.5 to 3 times of rated pressure to check the tolerance even though rated pressure range of these components are not ultra high pressure. So, the ultra high pressure system needs to be equiped to test components. In this study, safety assessments of ultra high pressure system which are using failure analysis of components, changing the types of the control system, and finite element analysis with static condition, are investigated.

• Proceedings of the KIEE Conference
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• 2006.10c
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• pp.288-290
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• 2006

This paper presents the real-time water tank wireless control in a ship using duplex RF modules and PLC(Programmable logic Controller). The purpose of this paper is developing HMI(Human Machine Interface) for automation equipments. The system can low a cost because long wires are no more used. Analog signals of the water gauge and flow meter are changed to discrete signals by the micro-processor. The PLC checks the volume of water and runs On or Off of the valve and pump. Duplex RF modules send and receive data between the water tank and control room. Everywhere the Internet is used, operators are able to check the status of the system by the web-server.

• Archives of Craniofacial Surgery
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• v.17 no.4
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• pp.225-228
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• 2016

The entrapment of intracranial air from the check valve system results in a tension pneumocephalus. It should be distinguished from simple pneumocephalus because they are intracranial space-occupying masses that can threaten life. Communicating hydrocephalus is a serious and frequent complication of post-traumatic head injury. Head injury is one of the most common causes in etiopathogenesis of communicating hydrocephalus. Here, we describe a case of a 65-year-old man who developed communicating hydrocephalus after a post-traumatic tension pneumocephalus. To the best of our knowledge, this is the first reported case of communicating hydrocephalus developed after a post-traumatic tension pneumocephalus. Although the exact pathogenic mechanisms underlying the cascade following trauma remain unclear, communicating hydrocephalus after a tension pneumocephalus could be considered a possible complication.

• Proceedings of the KSME Conference
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• 2003.04a
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• pp.1833-1838
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• 2003

In the nuclear power plant, emergency core coolant system(ECCS) is furnished at reactor coolant system(RCS) in order to cool down high temperature water in case of emergency. However, in this coolant system, thermal stratification phenomenon can be occurred due to coolant leaking in the check valve. The thermal stratification produces excessive thermal stresses at the pipe wall so as to yield thermal fatigue crack(TFC) accident. In the present study, when the turbulence penetration occurs in the branch piping, the maximum temperature differences of fluid at the pipe cross-sections of the T-branch with thermal stratification are examine

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.12
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• pp.2935-2944
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• 2000

Gas tungsten arc(GTA) welding is used to rrpiar the seat ring in swing type check valve in power plant because of its high weld quality. In order to automate the welding process, it is needed to analyze the process of inside pipe girth welding. In this study, the shapes of weld bead on pipe inside and outside were predicted and its validity was investigated. On the assumption that the welding arc had a bivariate gaussian distribution, analytical solution was derived to predict the temperature distribution in pipe weld using mapping under consideration of physical relationships. The size of weld bean could be predicted from this equation and its accuracy was verified by experiments.

• Journal of the Korean Institute of Telematics and Electronics B
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• v.31B no.10
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• pp.53-66
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• 1994

In this paper, a fuzzy expert system is developed for fault diagnoisis of a drum-type boiler system in fossil power plants. The develped fuzzy espert system is composed of knowledge base, fuzzification module, knowledge base process module, knowledge base management module, inference module, and linguistic approximation module. The main objective of the fuzzy expert system is to check the states of the system including the drum level and detect faults such as the feedwater flow sensor fault, feedwater flow control valve fault, and water wall bube rupture. The fuzzy expert system diagnoses faults using process values, manipulated values, and knowledge base which is built via interviews and questionaries with the experts on the plant operations. Finally, the validity of the developed fuzzy expert system is shown via experiments using the digital simulator for boiler system is Seoul Power Plant Unit 4.

• The KSFM Journal of Fluid Machinery
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• v.14 no.6
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• pp.26-34
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• 2011

Waterhammer and slamming phenomena can occur when power is cut off due to reversal flow in pipeline and sudden close of check valve. Therefore analysis of reversal flow time, which means the time of reversal flow in pipeline due to pumping station blackout, is needed to protect facilities from waterhammer economically and efficiently. However systematic study on reversal flow time has not been done yet. So theory of reversal flow time analysis is proposed and verified with experiment using several parameters like pump specific speed, motor pole number, and characteristic curve of pipeline in this study.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.11 no.1
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• pp.39-44
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• 2015

The fracture toughness of 2.25Cr-1Mo cast steel (SA217-WC9) samples which were taken from the check valves of feed water piping of Korean Standard Nuclear Power Plant(KSNPP) was measured by Master Curve method. The measured $T_0$ reference temperature of SA217-WC9 steel was $-30^{\circ}C$. The obtained $T_0$ was compared to the derived value from Charpy impact test data following to SINTEP procedure. The heat-to-heat variation in fracture toughness of SA217-WC9 steel was observed. It was found that the low toughness of a heat of SA217-WC9 steel was attributed to the coarse MnS inclusion originated by high sulfur content as the results of microanalyses.

• Transactions of the Korean Society of Automotive Engineers
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• v.3 no.6
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• pp.69-77
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• 1995

This paper presents performance investigation of a continuously variable ER(Electro-Rheological) damper for passenger vehicles. A dynamic model of the damper is formulated by incorporating electric field-dependent Bingham properties of the ER fluid. The Bingham properties are experimentally obtained through Couette type electroviscous measurement with respect to two different particle concentrations. The governing equation of the hydraulic model treating three components of fluid resistances;electrode duct flow, check valve flow and piston gap flow, is achieved via the bond graph method. A prototype ER damper is then designed and manufactured on the basis of parameter analysis. The damping forces of the system are experimentally evaluated by changing the intensity of the electric field, the particle concentration and the electrode gap.