• Proceedings of the KSME Conference
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• 2002.08a
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• pp.267-270
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• 2002

Combustion instability, which is one of the most undesirable phenomena in the development of liquid Propellant rocket engine, can cause serious damage to the rocket itself, and must be evaded by all means. Unfortunately, KSR-III rocket went through the combustion instability during engine start at the propulsion test article No.2. To resolve the problem, time sequence has been changed, and the baffle system has been applied. In consequence of the change, stable combustion was achieved.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2003.05a
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• pp.171-176
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• 2003

A Test Facility was established to carry out the integrated propulsion performance tests(IPPT). To perform IPPT's with maximum safety, an emergency blockage system was investigated. An emergency blockage system using combustion chamber pressure and acceleration signals was set up to monitor ignition delay and fail, flame out, propellant feeding status, unstable combustion and excessive structural vibration. With such system, the maximum safety could be secured by rapid judgement and follow-up measures, which made IPPT's be safely completed.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2003.05a
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• pp.193-196
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• 2003

The KSR-III developed by KARI is the first rocket vehicle which is adopting the liquid propellant rocket engine system in Korea and its flight test was successfully done last year. KSR-III is a sounding rocket class launch vehicle, but there is a sense to accomplish design, manufacture, performance test and finally its flight test by domestic technology. In this paper, the authors are intended to introduce the multi-purpose test facility(PTA-II Test Facility) which is constructed for the variety of tests on KSR-III feeding system(single component tests, verification tests, cold flow tests and combustion tests) and its test results.

• Proceedings of the KSR Conference
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• 2007.05a
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• pp.875-880
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• 2007

Due to increasing demands for environment-friendly railway system, bronze wires with cadmium, which is a potential environmental hazard, have been no longer permitted as messenger wire for electric railway system. One of materials being considered as the replacements is copper-clad steel conductor(CCSC), which is currently used as contact wire for high speed operation in the Japanese shinkansen. However, there have been few studies for the application as messenger wire by the CCSC. This study deals with requirements and performances of the messenger wire stranded by the CCSC, especially for high speed electric railway. And the tentative evaluation items and methods to be specified as the Korean railway standard(KRS) are proposed.

• Aerospace Engineering and Technology
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• v.11 no.1
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• pp.126-134
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• 2012

The Single Species, Unreacted Flow Model which is effectively applicable on the computational analysis of rocket exhaust flow is introduced in this paper. The basic concept of this model had been originated from chemically frozen analysis of hot air but it was complemented by compensating molecular weight and specific heat which was obtained CEA code analysis of exhaust plume. Comparing single species, unreacted model with the finite chemistry model, unreacted model can reduce calculation time to 1/5 while it makes similar simulation results.

• Proceedings of the KIEE Conference
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• 2015.07a
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• pp.1619-1620
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• 2015

KS C IEC 62561-2 표준은 피뢰시스템 구성요소로서의 도체 및 접지극에 관한 요구사항 및 시험에 대하여 규정되어 있다. 외부 피뢰 구성자재는 대기 중 혹은 대지에 직접 노출되어 있기 때문에 전기적 성능과 기계적 성능을 모두 만족해야 한다. 또한 피뢰도체와 접지극은 재질과 크기, 형태가 모두 다르기 때문에 각각의 요구사항에 부합할 수 있는 성능을 지녀야 한다. 본 논문에서는 일반적으로 많이 쓰이는 재질과 단면적을 가지는 접지봉으로 성능시험을 진행하였으며, 접지봉의 재료는 스테인레스강에 구리를 코팅한 동복강선으로 구성된다. 시험 결과 점착 시험 및 굽힘 시험에서 모두 크랙 및 코팅이 벗겨지는 것을 확인할 수 있었다. 코팅에 크랙 혹은 벗겨짐이 발생하면 지중에서 접지극의 부식이 진행되고, 접지저항이 높아져 전기적 성능을 저하시키는 결과를 야기한다. 때문에 스테인레스강에 구리 혹은 아연 등을 코팅하는 과정에서 벗겨짐이 없도록 점착 성능이 개선되어야 한다고 판단된다.

• Proceedings of the KSME Conference
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• 2000.11a
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• pp.274-279
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• 2000

The overhead transmission wires operating both at warm temperature and tighten state for a long period of time in a power transmission plant are degraded by air pollution, wind, creep and slip between steel wire and aluminium conductor. The objective of this study is to investigate a high carbon steel wire. We tested for basic mechanical properties and 3 types fatigue behavior, tension-tension, 4 points bending and 3 points bending fatigues. In this study, a conventional fatigue strengths between 4 points bending and tension-tension fatigue were determined by Gerber, Sorderberg and Goodman's theory and we investigated S-N diagram for bending and tensile loading.

• Journal of the Korean Institute of Rural Architecture
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• v.12 no.2
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• pp.23-29
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• 2010

Vinyl house is a simple agricultural structure that is installed economically and easily. In contrast, every year the farmers have spent a lot of money because of the collapse of this structure caused by the external forces such as strong wind and heavy snow. To prevent this damage due to frequent heavy snow and strong wind, it would be necessary to design it again. But getting rid of former vinyl house and reconstructing is unreasonable. It would be very economic if the former vinyl house is strengthened simply. This paper covers the investigation of the effect of the bracing systems that are additionally inserted inside the ordinary single frames as well as unbraced multiple frames that resisting only the strong wind load.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2007.04a
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• pp.283-288
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• 2007

This paper presents an analytical prediction of Nonlinear characteristics of prestressed concrete bridges by strengthened of externally tendon considering the work sequence, using beam-column element based on flexibility method and tendon element. The beam-column element was developed with reinforced concrete material nonlinearities which are based on the smeared crack concept. The fiber hysteresis rule of beam-column element is derived from the uniaxial constitutive relations of concrete and reinforcing steel fibers. The tendon element represent the bonded tendon and unbonded tendon behaviors. Beam-column element and tendon element was be subroutine A computer program, named RCAHEST (Reinforced Concrete Analysis in Higher Evaluation System Technology), for the analysis of RC and PSC structures was used. The proposed numerical method for prestressed concrete structures by strengthened of externally tendon is verified by comparison with reliable experimental results.

• Transactions of Materials Processing
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• v.25 no.5
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• pp.306-312
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• 2016

Effects of manufacturing conditions, such as austenitizing temperature, patenting temperature and carbon content in steels, on mechanical properties, especially on reduction of area (RA), of hyper-eutectoid steel wires were investigated. RA increased and then decreased with transformation temperature. This was attributed to the presence of abnormal structures in steels transformed at low transformation temperatures and the occurrence of shear cracking during tensile testing of steels transformed at high transformation temperatures. The increase of austenitizing temperature resulted in the increased austenite grain size and consequently the decrease of RA. The decrease of RA with increasing the carbon content in steels was attributed to the increased fraction of cleavage fracture in tensile fractured surfaces.