• Journal of the Korean Society for Railway
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• v.15 no.1
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• pp.42-47
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• 2012

There are ATC (Automatic Train Control), ATP (Automatic Train Protection), ATS (Automatic Train Stop) and ATO (Automatic Train Operation) etc. in train control systems. As various train control systems are installed according to sections, on-board signaling systems are installed to apply to the section. Hence, operation flexibility of trains is decreased. In other words, when trains are operated in the section where other train control systems are used, the on-board signaling systems are changed. Recently, a study on the combined on-board signaling system has been researched to solve this problem. The combined on-board signaling system consists of ATC, ATP and ATS device. Because the train control systems are vital, it needs to design the combined on-board signaling system by using k out of n system. In this paper, when k out of n system is applied in the combined on-board signaling system, the reliability and loss cost are analyzed by using failure rate in each device. Hence, the ideal number of systems is presented according to the number of outputs.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.42 no.5
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• pp.406-414
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• 2014

In this paper, it is introduced characteristics of FMCW-type Radar Altimeter for KUH, and its defects occurred during ground/flight test in initial product phase. In addition, it is also described 'data/control flow model' based fault analysis results of S/W and processes of verifying improvement design through flight test as well as aircraft system integration test called MEP SIL. As a result of design improvement and verification, it is validated that settling the defects and improving not only safety but also capability of the KUH.

• Journal of the Korean Geographical Society
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• v.43 no.2
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• pp.220-234
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• 2008

In many security monitoring contexts, the performance or efficiency of surveillance sensors/networks based on a single sensor type may be limited by environmental conditions, like illumination change. It is well known that different modes of sensors can be complementary, compensating for failures or limitations of individual sensor types. From a location analysis and modeling perspective, a challenge is how to locate different modes of sensors to support security monitoring. A coverage-based optimization model is proposed as a way to simultaneously site k different sensor types. This model considers common coverage among different sensor types as well as overlapping coverage for individual sensor types. The developed model is used to site sensors in an urban area. Computational results show that common and overlapping coverage can be modeled simultaneously, and a rich set of solutions exists reflecting the tradeoff between common and overlapping coverage.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.42 no.8
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• pp.707-712
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• 2014

Aircraft fuel indicator is a device to indicate the amount of fuel remained during flight, where accurate and consistent operation of the indicator should be maintained. Previously the Korean Utility Helicopter fuel indicator sporadically displayed abnormal sign by "8888" during flight, jeopardizing flight safety. Inappropriate EMI/EMC performance was detected during trouble shooting process. The cause of the abnormal display was found to be resulted from unstable power induced by electro-magnetic disturbance and CAN communication error. The aircraft fuel indicator design was improved and the design compatibility was verified to avoid abnormal display.

• Fire Science and Engineering
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• v.16 no.3
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• pp.8-11
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• 2002

Recently, the spark and the overheat due to in the failure of pressure contacts on connecting points and the momentary short circuit have been the major causes of electrical fire because these may cause the deposition and the graphite of insulating materials in electrical wiring system. Also, because in these cases the current is a surge one, the losses and faults of a communication, a home appliances, a computer and a measuring instrument may occur. Especially, in such cases, we are very difficult to detect the failure of pressure contacts on connecting points and the momentary short circuit. In this paper, we have developed an auxiliary control device, the electrical fire prevention control device(EFPCD), of an earth leakage breaker(ELB). And we can pre-vent the electrical fire caused by the spark and the overheat occurring in the failure of pressure contacts in connecting points and the momentary short circuit with the EFPCD.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.44 no.4
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• pp.316-323
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• 2016

A UAV(Unmanned Aerial Vehicle) flies along pre-programed navigation points(in-flight, take-off, or landing) automatically without pilot input. Even though UAVs fly differently from general piloted aircraft as the pilot controls the aircraft from a ground station through means of a data-link system. Occasionally, the data-link connection can be lost for any number of reasons, in which case, the FLCC(Flight control Computer) must automatically switch to autopilot to continue flying. Hence, the FLCC is a flight-critical component that must be throughly tested and validated. This paper discusses the development of a HILS(Hardware in the Loop Simulation) test environment designed to simulate real flight conditions to verify the FLCC satisfies flying quality requirements and maintains robustness despite any potential malfunctions or emergency situations.

• Journal of Energy Engineering
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• v.26 no.3
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• pp.113-122
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• 2017

The district heating system, which is the main axis of Korea's collective energy business, contributes to the national benefit and safety with the economical heat energy supply system.However, due to the uncertainty of management subjects and the shortage of professional technical personnel, there are many problems such as deterioration of thermal efficiency and unfairness of the price of the apartment houses. In this paper, we propose the monitoring points necessary for the efficiency and fault management of the district heating customer-side. And we propose a standard reference model to standardize it. We propose a technical methodology to improve the service quality and energy efficiency of the district heating facilities by applying IoT sensor technology, real-time monitoring and integrated management system.

• Korean Chemical Engineering Research
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• v.46 no.6
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• pp.1039-1042
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• 2008

In order to increase a functionality, OH value, for a recycled polyol prepared from the glycolysis reaction of a waste polyurethane rigid foam(PUR), the effect of an addition of pentaerythritol(PEN, functionality(f)=4) or sorbitol(SOR, f=6) to the its glycolysis reactor on the prepared polyol functionality and the mechanical properties of the polyurethane prepared using it was investigated. The OH values increased from 2.2 for a virgin to 2.8 for the recycled polyol. There was an increase in the mechanical properties including dimensional stability for PUR prepared using the recycled polyol, in which the increased OHs provided higher crosslinking density during PUR synthesis. In addition, the amount of the recycled polyol in the polyol system increased to from 8 to 20 wt% to give better mechanical properties to the PUR.

• Journal of the Korean Society for Railway
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• v.12 no.5
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• pp.670-677
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• 2009

This paper is a study of testing on-board signalling equipment in advanced high speed rail at the maximum speed of 400km/h. The on-board signalling equipment in advanced high speed rail provides operating information to the driver when operating at ATC, ATS, and ATP sections, and maintains safety from driver oversight, signalling equipment malfunction, natural disasters and so on. Since the testing train performance of advanced high speed rail at 400km/h must include the function test of on-board signalling equipment, this thesis focuses on the function test of on-board signalling equipment and analyze the necessity of the test at the maximum speed. Finally, it is suggested to change some infrastructure and to use specific test methods to test the train performance at the maximum speed in high speed line ATC section.

• Journal of Korean Tunnelling and Underground Space Association
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• v.22 no.2
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• pp.197-217
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• 2020

Shield TBM tunneling, used in the construction of Seoul subway line 7 and line 9, has been well known as a very efficient, as well as safe, tunneling method. Although the Shield TBM method has been known to be effectively used in poor ground conditions, a number of troubles have occurred during the use of the shield TBM, due to inappropriate machine selection, machine breakdown, and unpredicted ground conditions etc. In this study, several accidents and trouble cases occurred during excavation by Shield TBM, reported from Japan, were investigated. A series of numerical analysis was then performed to compare with the trouble cases and back-analysis results for the cause analysis. The lessons learned from the case studies are presented at the end.